FOUS11 KWBC 092037
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
337 PM EST Sun Nov 9 2025

Valid 00Z Mon Nov 10 2025 - 00Z Thu Nov 13 2025

...Great Lakes to Interior Northeast and Appalachians...
Days 1-2...

Leading shortwave impulse/vort max lifts northward over Lake
Ontario tonight as an area of low pressure reloads on Monday over
New England as the deep upper low swings across the Ohio Valley.
This setup will provide warm air advection mixed ptype into
northern New England, the northern Adirondacks, and St.Lawrence
river valley through tonight before cold air advection returns to
the region Monday into Tuesday. Light freezing rain is expected in
at least pockets from the Tug Hill through the Adirondacks and
north as well as the White Mtns of NH/ME. WPC probabilities for

0.1" ice accretion are between 30-50%% in northern NY and closer

to 30% for the White Mtns.

...Lake Effect/Enhanced Snow through Tuesday...
Deepening upper-low drops southward from the Great Lakes tonight to
the southern/central Appalachians Monday night, with heights
dropping into record levels for early-mid November. This will lead
to the first major lake effect and Appalachian upslope snow event
of the season as bitter cold Canadian air rushes over the warm
Great Lakes. The pivoting and depth of the developing strong upper
low over the Great Lakes region will prolong the cold air advection
flow and thus lake effect/enhanced snow from Lake Superior through
Monday with single banding likely off Lake Michigan tonight/Monday
with Huron/Erie/Ontario LES late tonight through Tuesday.
Favorable QPF spreads through all the Great Lakes before easing off
Lake Ontario on Tuesday.

The cold airmass, headlined by 850mb temperatures between negative
10 and 12 degrees C over the warm Great Lakes (temperatures of +10
to +15C) will result in an impressive convective environment with
model soundings indicating steep lapse rates and deep mixing
heights to near or above 700mb. Given lake temp and 850mb air temp
delta Ts of 20 to 30C, the environment will be rather supportive
for lake effect/enhanced snow production and likely periods of
thundersnow.

North-northwest to northerly surface winds along with increasingly unidirectional winds aloft will act on the instability and support
the development of a few prominent north-south lake effect snow
bands, particularly downwind of Lake Superior through Monday, Lake
Michigan tonight through Monday, Lakes Huron and Erie late tonight
through Monday night, and Lake Ontario Monday night/Tuesday.
Decent confidence in heavy banding spreading west into the Chicago
metro this evening as CAMs develop a mesolow over southern Lake
Michigan and help enhance the intense snow rates around 2-3"/hr
along the western shores before drifting back east through Monday
morning. Localized totals over 1 foot are possible (10-20%) in
northwest IN depending on how long the single Lake Michigan
snowband can remain in tact. Here, major impacts are possible due
to very intense snowfall rates and extend into the highly
populated region of northwest IL tonight. In addition, cold
upslope northwesterly flow and a moist fetch from Lake Michigan
will also cause upslope snow showers for the Central/Southern
Appalachians tonight through Monday night with Days 1-2 WPC
probabilities for >6" 40-70%. Days 1-2 snow WPC probabilities for

8" are 30-60% in northeast IL, northwest IN, the central Appalachians/Alleghenies, and southern Appalachian crest.

Additional 50-80% Day 2 WPC probabilities for >8" exist along the
shoreline of Lake Erie from northwest PA into far western NY and
along the southern shoreline of Lake Ontario between Wayne and
Oswego counties. As always the case with lake effect snow, amounts
and impacts could drastically differ over the span of tens of miles
depending on where snowbands situate.



Snell/Jackson





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FOUS11 KWBC 160800
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
300 AM EST Sun Nov 16 2025

Valid 12Z Sun Nov 16 2025 - 12Z Wed Nov 19 2025

...Northeast/Great Lakes...
Days 1-2...

A vigorous shortwave will slide east of the Great Lakes this
morning, with a closed upper center forecast to develop over New
England later today. At the surface, a low pressure center is
expected to redevelop along the Maine coast this morning and track
east into southern New Brunswick by this evening. This track will
support snow across interior Maine, with rain along the coast,
followed by a transition to snow as far south as Downeast Maine as
the low tracks into Canada. The heaviest amounts across Maine are
likely to center over the North Woods, with WPC probabilities
continuing to indicate that amounts over 4 inches are likely to
cover the region, with locally heavier amounts over 8 inches
possible in the higher terrain.

Meanwhile, any lingering mixed precipitation from the overnight
falling over northern New York, Vermont, and New Hampshire is
likely to transition to all snow early in the period, with upslope
snow beginning to ramp up this morning. Little change to the
previous forecast, with northwest flow targeting parts of the
northern Adirondacks, Greens, and Whites with the best chance for
significant accumulations. The heaviest accumulations are expected
today. But with some additional accumulations continuing through
Monday, two day totals likely expected to top a foot in some
locations, especially in the northern Greens and the Presidential
Range.

The cold air advection and west-northwesterly to northwesterly
flow will support multiple lake effect bands off of Lake Ontario,
producing some locally heavy totals around the Finger Lakes. A
narrow intense single band with connections to lakes Superior and
Huron may set up downwind of Lake Erie, resulting in some locally
heavy totals near the far western New York-Pennsylvania border
into northwestern Pennsylvania. These are reflected in some higher
WPC probabilities for snowfall amounts exceeding 4 inches in those
areas.

...California to the Central and Southern Rockies...
Days 1-3...

A pair of upper lows will impact the region this period. The first
system, which is currently, producing widespread precipitation
across central to southern California and parts of Nevada and
Arizona this morning, is forecast to lift northeast across
southern California into the Great Basin later today, before
continuing east across the central Rockies tonight into early
Monday. This will be followed by a highly amplified shortwave
dropping out of the northeastern Pacific, with a closed low
developing near the northern California coast tomorrow. This second
system is then expected to continue to drop south, moving into
southern California on Tuesday.

For the leading low, additional accumulations of 6 inches or more
are likely for parts of the Sierra Nevada, mainly for areas above
9000 ft in the southern Sierra and above 7000 ft in the central to
northern Sierra. Farther to the east, this system may produce
similar totals, mostly for areas above 9000 ft, across the southern
Utah mountains and the Rockies from areas as far south as the San
Juans to as far north as the Teton and Wind River ranges.

Heavy accumulations with the second low will focus mostly on the
Sierra Nevada once again, with early Monday to early Wednesday two-day
totals expected to exceed 8 inches for many areas above 7000 ft in
the central Sierra. Some of the higher elevations in the central
and southern Nevada and the southern Utah mountains, as well as
the San Juans could also see locally heavy totals.

Pereira

$$

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FOUS11 KWBC 161905
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
205 PM EST Sun Nov 16 2025

Valid 00Z Mon Nov 17 2025 - 00Z Thu Nov 20 2025

...Northeast/Great Lakes...
Days 1-2...

Amplifying closed mid-level low will continue its slow trek into
the Canadian Maritimes tonight through Monday, but wintry
precipitation will continue in earnest across portions of Northern
New England and Upstate New York.

While the primary warm conveyor will pivot well east and away from
the United States, a modest TROWAL will persist into northern Maine
bringing some pivoting/comma head snowfall with rates of 0.5-1"/hr
at times. This combined with increasing northerly winds will bring
moderate impacts to the north and east portions of the state,
especially the first half of the period, before the DGZ dries out
and precip wanes. WPC probabilities for additional snowfall
exceeding 4" in northern/eastern Maine are generally 30-50%.

The more significant snowfall is expected farther west into the
terrain of central ME and across NH, VT, and Upstate NY. This will
be in response to prolonged and impressive upslope flow as NW winds
develop and strengthen behind the departing low pressure system.
The guidance is in good agreement that unidirectional NW flow will
persist D1 and into D2, bringing periods of heavy snow as ascent is
forced into the deepening DGZ and moistening the lower half of the
resultant column. This should provide an environment favorable for
heavy snow into Tuesday, and with Froude numbers indicating
critical flow, the focus should be along the crests of the higher
terrain and just upwind. With snowfall rates from the HREF progged
to exceed 1"/hr at times, this will produce heavy accumulations for
which WPC probabilities are high (>70%) for an additional 6+ inches
of snow in the northern Adirondacks, Greens, and portions of the
Whites of NH and ME, with locally up to 1 foot of snowfall possible
(10-30%). Precipitation will wane on Tuesday with snow likely
ending Tuesday aftn.

Finally, the pronounced CAA on NW flow behind this system will
cross the Great Lakes and produce some narrow bands of lake effect
snow (LES), especially downwind of Lake Superior and Lakes
Erie/Ontario. While this direction is not ideal for elongated fetch
across the lakes, the high-res guidance is in good agreement that
an upstream connection will occur from Superior, to Huron, to Erie,
with an additional upstream band from Georgian Bay to Lake
Ontario. This should produce narrow corridors of heavy snowfall
exceeding 1"/hr on D1, leading to accumulations for which WPC
probabilities indicate have a 50-90% chance of exceeding 4 inches
across the Chautauqua Ridge, the Tug Hill Plateau, and portions of
the eastern Finger Lakes region, with the latter continuing through
D2.


...California to the Central and Southern Rockies...
Days 1-3...

A pair of upper lows embedded within persistent troughing across
the West will bring periods of high-elevation heavy snow to
portions of the region.

The first will be associated with a compact shortwave lifting
across UT/WY/CO that will deepen into a closed feature as it moves
into the Central High Plains Monday afternoon. The amplification of
this wave will result in increased deformation to its west,
aligning with modest upper diffluence as a weak jet streak develops
in the vicinity. This paired ascent occurring within a moist column
(PWs above the 99th percentile) will result in a transition to
heavy snow through dynamic cooling, especially in the higher
terrain of CO and WY above 7000 ft. WPC probabilities for more
than 6 inches of snow are high (>70%) from the Wind Rivers through
portions of the Uintas and into much of the CO Rockies, with
locally as much as 12 inches possible in the Wind Rivers and the
Park Range.

Upstream of this feature, a more pronounced upper low will dig
slowly along the CA coast, tracking into Baja Wednesday before
finally beginning to eject eastward late in the forecast period.
Downstream of this feature, another round of impressive IVT
exceeding the 90th percentile according to NAEFS ensemble tables
will surge eastward into CA and the Great Basin, reaching the Four
Corners states Wednesday. Beneath the upper low, snow levels will
fall to 5000-5500 ft, but within the plume of IVT and accompanying
WAA, which is also where the heaviest precipitation is expected,
snow levels will remain elevated at 7000-9000 ft. This will result
in heavy snowfall, initially in the Sierra, then spreading east
into the Great Basin and Four Corners terrain including the San
Juans, Wasatch, and portions of the Mogollon Rim (White Mountains
of AZ area). WPC probabilities D1-2 are high (>70%) for 6+ inches
in the Sierra and the higher terrain of the Great Basin and into
the Wasatch and San Juans, where locally 1-2 feet of snow is likely
by the middle of the week.


...Central Plains/Upper Midwest...
Day 2...

Compact mid-level shortwave will close off as it crosses from
Nebraska to the Great Lakes Monday night and Tuesday. Significant
mid-level moisture advection ahead of this feature will spread
precipitation northwards into the Dakotas and then eastward through
the Upper Midwest. On the north side of this precipitation shield,
soundings suggest the column will be marginally thermally favorable
for snowfall. However, cross-sections indicate an increasing threat
for CSI where theta-es decreases with height, directly into the DGZ
to support intense snow growth. Additionally a deep isothermal
layer beneath the DGZ indicates a favorable setup for aggregate
maintenance and large snow flakes with efficient accumulation.

The guidance, especially the available high- res, has become more
aggressive with this development, and it is likely that this ascent
will cause rapid dynamic cooling of the column to support a narrow
band of heavy snowfall which will track slowly from near the
Coteau des Prairies through far southeast Wisconsin. While there is
still pronounced latitudinal spread and timing differences,
confidence is increasing that a band of heavy snow, with rates of
at least 1"/hr, will move across the area. This is supported by
increasing snowfall probabilities in both the NBM and the AIFS, and
the updated WPC probabilities for at least 1" of snowfall have
increased to above 70%. Locally much heavier snow is possible, and
future updates will need to be monitored for this potential.


Weiss


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FOUS11 KWBC 170805
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
305 AM EST Mon Nov 17 2025

Valid 12Z Mon Nov 17 2025 - 12Z Thu Nov 20 2025

...Northeast/Great Lakes...
Day 1...

A deep closed low now centered over the Canadian Maritimes will
begin to lift north this morning and then accelerate later in the
day. Supported by deep northwesterly to west-northwesterly winds in
its wake, ongoing orographic and lake effect snow showers will
continue but gradually wane through the day. The northern
Adirondacks, Green, and White mountains will remain the focus for
upslope snows, with some potential for several more inches in some
spots, especially along the northern Greens, where WPC
probabilities for additional accumulations exceeding 4 inches
remain high.

Further to the west, there is a decent signal for a single band
intensifying off of Lake Ontario and shifting east across the
Finger Lakes, with WPC probabilities indicating several inches are
possible east-southeast of Syracuse.

Lastly, the band off of Lake Erie with a connection extending back
to Lake Superior is expected to wane and shift east, most likely
producing just another inch or two across parts of southwestern New
York and northwestern Pennsylvania today.

...California to the Central and Southern Rockies...
Days 1-2...

An upper low will move across Colorado and Wyoming this morning.
Snow will continue to fall this morning across the western and
south-central Wyoming ranges, as well as the western Colorado
mountains, with additional accumulations remaining light for most
areas. Favorable upper jet-streak forcing along with moist
southwesterly flow may support some higher totals along the Sierra
Madre, Park Range, and Medicine Bow mountains in south-central
Wyoming and north-central Colorado. WPC probabilities indicate
additional totals over 4 inches are likely, especially for areas
above 8,000 ft.

A second low closing off within the base of a sharp trough
approaching northern California will continue to deepen and drop
south along the coast through today into early tomorrow. This
system is expected to linger as it settles along the southern
California coast tomorrow before rotating inland as yet another
Pacific system moves toward California late Wednesday into
Thursday.

Areas of heavy snow are forecast to spread south along the Sierra
Nevada today, before diminishing tonight, but with light amounts
continuing across parts of the central and southern Sierra through
Tuesday. WPC probabilities indicate that two-day totals are likely
to exceed 8 inches for many locations in the central Sierra above
8,000 ft. Some locally heavy totals, exceeding 8 inches, are also
expected farther east in parts of the central and southern Nevada
ranges, and the southwestern Utah mountains.

...Central Plains/Upper Midwest...
Days 1-2...

The previously noted low exiting the Rockies today is forecast to
move steadily east from the Central Plains into the mid and upper
Mississippi Valley tonight. Low to mid level frontogenesis along
with a coupled upper jet will support a stripe of moderate
precipitation developing from eastern South Dakota, through
southern Minnesota, into southern Wisconsin tonight. Dynamic
cooling will support rain changing to snow where this heavier band
sets up. While probabilities for accumulations beyond an inch or
two remain low, the potential for locally heavier amounts cannot be
ruled out.

Pereira

$$

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FOUS11 KWBC 120744
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
344 AM EDT Sun Oct 12 2025

Valid 12Z Sun Oct 12 2025 - 12Z Wed Oct 15 2025

...Northern Rockies & Pacific Northwest...
Days 1-2...

By the start of the forecast period (12Z Sunday), a potent
shortwave upper-level trough will be quickly exiting the northern
Rockies along with an associated strong surface low pushing
northeastward into southern Saskatchewan. Gradually increasing
heights are then expected across the northern Rockies through the
remainder of the day 1 forecast period, while a rapidly deepening
upper low drops southward along the coast of the Pacific Northwest.
At the surface, cold Canadian high pressure nosing southward into
northwest MT will allow for favorable upslope ascent in this
region, with general low-to-mid level convergence extending across
northern WA and ID along a sinking frontal boundary. This will
favor light to moderate snow across areas above 5,000ft, but with
snow levels dropping enough for flakes to reach into parts of the
MT Front Range and adjacent High Plains at times on Sunday night.
For the Cascades of WA and OR, snowfall will be tied to the
dropping upper low as snow levels start around 4,000-5,000ft
(lowest in the northern WA Cascades) before eventually lowering to
around 3,000ft in WA and 4,500ft in OR on day 2.

WPC probabilities show moderate-to-high probabilities (50-80%) for
storm-total snowfall amounts >8" from the Cascades on eastward into
the northern Idaho Panhandle to the Lewis Range of Montana.
Mountains within and around Glacier Nat'l Park even have moderate
chances (40-60%) for over 12" of snow, particularly above 7,000ft.
The WSSI shows mostly Minor Impacts due to potentially slick travel
conditions, while some passes in Montana and Glacier Nat'l Park
may contend with Moderate Impacts that could result in road
closures.

...California...
Days 2-3...

...First heavy snowfall event of the season set to impact the
Sierra Nevada beginning Monday night...

By day 2, the upper low dropping southward along the West Coast is
forecast to deepen into a robust 500mb low off the northern
California coast. This sudden amplification of the 500mb trough
(18Z ECMWF shows 500mb heights below the 0.5 climatological
percentile and nearing October records off the California coast
Monday afternoon) is due to an impressive anti- cyclonic weak break
over British Columbia. The dramatic height falls and modest
500-700mb CAA aloft will support lowering snow levels down to
around 6000-6500ft through the Siskiyou and the Sierra Nevada
starting Monday and continuing into the first half of next week.
All guidance also shows a healthy IVT topping 400 kg/m/s helping to
direct plenty of Pacific moisture at the mountain ranges. Snow
arrives over the northern California mountains on Monday with the
heaviest snowfall occurring Monday night into Tuesday over the
Sierra Nevada. Guidance has come in snowier over the past 12-24
hours, and given the lack of deep, cold air aloft, snow is likely
to be a heavy/wet snowfall along the Sierra Nevada. This could
raise concerns for potential impacts to trees and infrastructure
given this is the first significant mountain snowfall in the Sierra
Nevada this season.

WPC probabilities show moderate-to-high chances (50-80%) for at
least 24" of snowfall throughout the central Sierra Nevada (above
8,000 feet) by Wednesday morning, with maximum amounts up to 36"
possible. Latest WSSI-P shows high chances (70-99%) for Moderate
Impacts along the central Sierra Nevada with the Snow Amount, Snow
Load, and Snow Rate impacts being the main concerns for the first
significant snow of the season. Current WSSI also highlights Major
to Extreme Impacts, which would imply difficult to impossible
travel at times between Monday night and much of the day on Tuesday,
including for many major passes.


The probability of significant freezing rain across CONUS is less
than 10 percent.


Snell/Mullinax





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FOUS11 KWBC 121913
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
313 PM EDT Sun Oct 12 2025

Valid 00Z Mon Oct 13 2025 - 00Z Thu Oct 16 2025

...Northern Rockies & Pacific Northwest...
Days 1-2...

Snow has subsided in parts of WY and central ID as the 500mb
shortwave trough responsible for snowfall late yesterday and
overnight tracks into south-central Canada. However, periods of moderate-to-heavy snow will linger over western MT as cold
Canadian high pressure nosing southward allows for favorable
upslope ascent in this region, with general low-to-mid level
convergence extending across northern WA and ID along a sinking
frontal boundary. This will favor light to moderate snow across
areas above 5,000ft, but with snow levels dropping enough for minor accumulations for parts of the MT Front Range and adjacent High
Plains above 4,000ft through tonight. For the Cascades of WA and
OR, snowfall will be tied to the amplifying upper low emerging from
British Columbia as snow levels start around 4,000-5,000ft (lowest
in the northern WA Cascades) before eventually lowering to around
3,000ft in WA and 4,500ft in OR on Monday

WPC probabilities show moderate-to-high probabilities (50-80%) for
storm-total snowfall amounts >8" from the Cascades on eastward into
the northern ID Panhandle to the Lewis Range of MT. Over western
MT and the ID Panhandle, including Glacier Nat'l Park, an
additional... particularly above 7,000ft. The WSSI shows mostly
Minor Impacts, signaling potentially slick travel conditions, while
some passes in MT and Glacier Nat'l Park may contend with Moderate
Impacts that could result in road closures.

...California & Central Nevada...
Days 2-3...

...First significant snowfall event of the season set to impact
the Sierra Nevada beginning Monday night...

The upper low dropping southward along the West Coast is forecast
to deepen into a robust 500mb low off the California coast. This
amplification of the 500mb trough (06Z ECMWF shows 500mb heights
below the 0.5 climatological percentile and nearing October records
off the California coast Monday afternoon) is due to an impressive anti-cyclonic wave break over British Columbia. Height falls and
modest 500-700mb CAA aloft will support lowering snow levels down
to around 6000-6500ft through the Siskiyou and the Sierra Nevada
starting Monday and continuing through the first half of next week.
A healthy IVT topping 400 kg/m/s is helping to direct a rich plume
of Pacific moisture at the mountain ranges. Snow arrives over the
northern California mountains on Monday with the heaviest snowfall
occurring Monday night into Tuesday over the Sierra Nevada. Given
the lack of deep, cold air aloft, snow is likely to be a heavy/wet
snowfall along the Sierra Nevada. This raises concerns for
potential impacts to trees and infrastructure given this is the
first significant mountain snowfall in the Sierra Nevada this
season. WPC's Snowband Probability Tracker shows HREF guidance
identifying 2-3"/hr rates over the central Sierra Nevada Monday
night. Look for some heavy snowfall to spill into central Nevada's
taller ranges with anywhere from 6-12" of snowfall possible.

WPC probabilities show moderate-to-high chances (50-80%) for at
least 24" of snowfall throughout the central Sierra Nevada (above
8,000 feet) through Wednesday with maximum amounts exceeding 36"
possible. Latest WSSI-P shows moderate-to-high chances (50-80%)
for Major Impacts along the central Sierra Nevada with the Snow
Amount, Snow Load, and Snow Rate impacts being the main concerns
for the first significant snow of the season. Current WSSI also
highlights Moderate to Major Impacts, which would imply difficult
to impossible travel at times between Monday night and much of the
day on Tuesday, including for many major passes.


The probability of significant freezing rain across CONUS is less
than 10 percent.


Mullinax/Snell






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FOUS11 KWBC 260900
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
500 AM EDT Sun Oct 26 2025

Valid 12Z Sun Oct 26 2025 - 12Z Wed Oct 29 2025


...Pacific Northwest to the Central Rockies...
Days 1-2...

The primary shortwave axis will be positioned well inland, near
the Northern Rockies, to begin the period /12Z Sunday/, but a
secondary impulse and accompanying surface wave will move onshore
near the OR/CA border this evening. The accompanying pinched and
confluent mid-level flow will continue to advect higher moisture
onshore, leading to a second wave of heavy precipitation moving
from the Cascades early today into the Northern Rockies by early
Monday.

This second wave of precipitation will occur behind the primary
cold front, and during a period of continued height falls, so snow
levels will fall steadily through D1. The latest NBM snow level
forecasts have trended downward, reaching as low as 2000 ft in the
eastern Cascades, to around 3500 ft in parts of OR/MT/ID. This will
occur in tandem with waves of precipitation, such that even though precipitation intensity may be less than what occurred Saturday,
pass level impacts will be more substantial due to the lower snow
levels. This wave moves quickly east, however, and by Monday night precipitation should generally wane across the region.

WPC probabilities are high (>70%) for 6+ inches across the Cascades
and into portions of the Salmon River ranges D1 before waning
quickly during D2. Passes will likely become hazardous D1 due to
low snow levels, especially around Stevens and Santiam Passes in
the Cascades.


The probability of significant ice across the CONUS is less than
10 percent.


Weiss


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FOUS11 KWBC 261939
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
339 PM EDT Sun Oct 26 2025

Valid 00Z Mon Oct 27 2025 - 00Z Thu Oct 30 2025


...Cascades and Northern/Central Rockies...
Day 1...

The third and final shortwave trough axis with the troughing over
the Northwest the past couple of days is pushing over the OR coast
this afternoon. This axis reaches central MT by 18Z Monday and will
provide the focus for moderate to locally heavy snow over the
Cascades and northern Rockies that mainly tapers off for the
Cascades Monday morning and Monday evening for the northern
Rockies. Snow levels drop further under this trough, to around
3000ft in the WA Cascades tonight and the Bitterroots Monday
morning, and around 3500ft in the OR Cascades through Sawtooths of
ID and around Yellowstone (Absarokas, Tetons, Wind River) and about
4500ft for the Bighorns.

Day 1 WPC probabilities are high (50-80%) for >8" for the Tetons,
southern Absarokas, Wind River, and Bighorns while moderate
(40-60%) for >6" for the higher Cascades, Blue Mtns of OR,
Bitterroots and Lewis Range, Uinta of UT and the Medicine Bow/Park
Range along the WY/CO border.

Lee-side troughing should allow some higher elevation snow in
eastern WY and the Black Hills Monday evening.


...Washington Cascades...
Day 3...

A potent, but progressive low pushes across the BC coast Tuesday
night with a trough axis extending south over Washington State.
High snow levels around 8000ft Tuesday afternoon in the elevated
moisture plume quickly crash to around 4500ft by the time the
trough crosses and precip cuts off. Day 3 snow probabilities for

6" are 20-40% around North Cascades NP.

The probability of significant ice across the CONUS is less than
10 percent.


Jackson



$$

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FOUS11 KWBC 270735
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
335 AM EDT Mon Oct 27 2025

Valid 12Z Mon Oct 27 2025 - 12Z Thu Oct 30 2025


...Northern/Central Rockies...
Day 1...

Persistent moisture on confluent west to east flow impinging into
the Northwest will be acted upon by height falls/PVA through the
last in this series of shortwaves moving from ID into MT and WY
today into tonight. This feature will be quickly followed by
shortwave ridging in its wake, bringing an end to precipitation by
the end of D1. Snow levels will remain relatively low, around 3500
ft west, 4500 ft east, with several inches of snowfall likely above
these levels, leading to at least scattered pass level impacts.
WPC probabilities D1 indicate a high chance (>70%) for additional
snowfall above 6" in the Tetons and Big Horns, with light snow
accumulating to a few inches likely in the CO Rockies, the
Northern Rockies, and even into the higher Black Hills.


...Washington Cascades...
Day 2...

A potent, but progressive low pushes across the BC coast Tuesday
night with a trough axis extending south over Washington State. A
brief period of enhanced moisture noted in regional soundings will
result in transient but heavy precipitation, driven by a narrow
corridor of intense 700-600mb fgen late Tuesday night. The
strongest fgen appears to efficiently intersect the DGZ, which will
deepen as colder air floods eastward behind the accompanying
shortwave. While the heaviest precip will likely occur with snow
levels around 8000 ft limiting pass-level impacts, they will crash
quickly, aided by the heavy precipitation rates, to around 4500 ft
before precipitation wanes. This results in WPC probabilities for
more than 4" of snow reaching 70-90% across the highest terrain of
the WA Cascades, with a few inches of snow likely at Washington
Pass.


The probability of significant ice across the CONUS is less than
10 percent.


Weiss


$$

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FOUS11 KWBC 181926
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
226 PM EST Tue Nov 18 2025

Valid 00Z Wed Nov 19 2025 - 00Z Sat Nov 22 2025

...California through the Southern Rockies...
Days 1-3...

A series of upper lows tracking into the southwestern U.S. will
continue through the remainder of the work-week that will keep
mountain snow in the forecast from the Sierra Nevada and the peaks
of the Transverse Ranges to as far east as the CO/NM Rockies.

The current stretch of active weather is due to an upper low over
southern CA that is directing a swath of rich subtropical moisture
and generating large-scale vertical ascent over the Southwest. A
lack of a sub-freezing antecedent air-mass is making the more
remote mountains ranges of the southern Sierra Nevada, northern AZ,
southern UT, and CO's San Juan Mountains as the favored locations
for measurable snow through Wednesday evening. By Wednesday night,
the 500mb upper low opens up into a potent shortwave trough that
takes on a negative tilt over the Gulf of California, resulting in
increased divergence aloft and a healthier influx of moisture into
the southern Rockies. While snow levels may dip to as low as 7,000ft
in parts of NM and CO, the bulk of the heavier snowfall totals
will be confined to elevations above 9,000ft in the San Juans and
Sangre De Cristo. The heaviest snowfall transpires in these
mountain ranges on Thursday and persists with lighter amounts into
Friday morning. WPC probabilistic guidance shows moderate-to-high
chances (50-80%) for snowfall totals >8" and low-to-moderate
chances (20-40%) for snowfall totals >12" for elevations above
9,000ft in southern CO and northern NM, while similar probabilities
for snowfall totals >8" also exist for southern UT mountain ranges
above 8,000ft.

At the same time as the current upper-level trough goes negative
tilt over northern Mexico early Thursday morning, another upper low
off the West Coast tracks south along the CA coast on Thursday. By
Friday, the upper low is forecast to reside over the southern CA
coast with a near carbon-copy setup to Tuesday's upper-level
pattern. Snow will start to unfold in Salmon/Trinity/Siskiyou of
northern CA early Thursday morning, followed by the Sierra Nevada
throughout the daytime hours on Thursday. Snow levels may dip as
low as 5,000ft, but only minor snowfall accumulations are
anticipated below 6,000ft. The heavier snowfall totals are most
likely to unfold at elevations above 7,000ft in the Sierra Nevada
through Friday morning. This new upper-low will perform a similar synoptic-scale evolution to Tuesday's low, but this time it will
track a little farther south and west, resulting in lesser
concerns for snow in the higher mountain ranges of southern NV,
northern AZ, and southern UT. WPC probabilities depict moderate
chances (40-60%) for snowfall totals >4" along the Sierra Nevada
above 7,000ft with low chances (10-30%) for elevations >9,000ft in
the southern Sierra Nevada receiving >8" of snow. The peaks of the
San Gabriel and San Bernadino Mountains (above 7,000ft) also have
moderate chances (40-60%) for snowfall totals >4" late Thursday
night and into Friday.


Mullinax



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FOUS11 KWBC 190800
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
300 AM EST Wed Nov 19 2025

Valid 12Z Wed Nov 19 2025 - 12Z Sat Nov 22 2025

...California through the Southern Rockies...
Days 1-3...

An upper low centered over Southern California this morning will
slowly translate eastward over the next 24 hours before the next in
a series of developing lows approaches the coast and begins to
eject it eastward. As the leading low moves east, it will continue
to direct deeper moisture and associated mid level energy farther
inland. With high snow levels in place at the onset, there will be
little threat for widespread heavy snow accumulations through early
Thursday. WPC's Day 1 probabilities shows the threat for
accumulations above 6 inches to be isolated and mostly confined to
the higher peaks of the southern Utah Mountains, the San Francisco
Peaks and White Mountains in Arizona, and the San Juans in
southwestern Colorado.

As the leading system moves east, the extent of light snow
accumulations is forecast to increase across the Colorado and
northern New Mexico ranges. However, accumulations greater than 6
inches will likely be limited to areas in the San Juans and Sangre
de Cristos above 10,000 ft.

Meanwhile, mountain snow will spread quickly south across
California from the southern Cascades to the northern Transverse
Ranges on Thursday. Given the progressive nature of this second
system and more modest moisture, widespread heavy snow
accumulations are unlikely. WPC probabilities for 24 hour amounts
exceeding 6 inches are limited mostly to the higher peaks of the
Sierra Nevada.

Similar to its predecessor, this second low is expected to settle
and linger over Southern California Friday into Saturday. The
footprint for heavy snow is expected to become even more
confined, limited to the higher peaks of the Transverse Ranges and
perhaps the southern Nevada mountains.

Pereira

$$

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FOUS11 KWBC 191858
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
158 PM EST Wed Nov 19 2025

Valid 00Z Thu Nov 20 2025 - 00Z Sun Nov 23 2025

...Southern & Central Rockies...
Days 1-2...

An upper low tracking through the Desert Southwest today will
sharpen up and take on an increasingly negative tilt over northern
Mexico tonight and into Thursday morning. Healthy 500mb PVA and an
influx of moisture (courtesy of IVT values topping 400 kg/m/s that
exceed the 97.5 climatological percentile per ECMWF SATs) will
be the key ingredients in a blossoming area of precipitation over
AZ, NM, southern UT, and southern CO. Temperatures aloft are not
overly cold and the antecedent air-mass is generally mild, thus
forcing most of the impending snowfall to occur in the more
remote/higher terrain of the Southern Rockies.

As the upper trough reaches the Southern Plains Thursday night,
the 500mb trough will become inverted with a narrow tongue of
easterly upslope flow still producing a persistent light-to-
moderate snow in the forecast into Friday morning. Snow levels for
the event may dip as low as 6,000ft in parts of the Wasatch and as
far south and west as Zion Nat'l Park, but the bulk of the more
impactful snowfall totals will reside above 7,000ft in the
mountains surrounding Las Vegas and the southern Wasatch, above
8,000ft in the Mogollon Rim and Gila Mountains of AZ, above
9,000ft in the San Juans and Sangre De Cristo, and above 10,000ft
along the CO Front Range. WPC probabilities show most of these
ranges above the listed elevations are likely to see at least 4"
of snowfall, but it will be in these mountains' more
remote/elevated reaches that sport low-to-moderate chances
(30-50%) for snowfall totals >8" through Friday.

...California...
Days 1-3...

As this lead upper-trough tracks towards the South-Central U.S. on
Thursday, the next Pacific upper-level trough is hot on its heels
as it dives southward along the CA coast. A progressive system, it
will produce a swath of accumulating snowfall at/above 5,000ft
from the Trinity/Siskiyou mountains of northern CA on south along
the Sierra Nevada and even the peaks of the Transverse and
Peninsular ranges. The heaviest snowfall for the Sierra Nevada is
expected on Thursday with snowfall tapering off by Friday morning.
WPC probabilities depict moderate-to-high chances probabilities
(50-8%) for snowfall totals >6" in the central and southern Sierra
Nevada with localized totals approaching 12" in the >10,000ft
peaks.

Snow will pick up in intensity over the peaks of the San Gabriel
and San Bernadino mountains starting Thursday afternoon and lasting
through Friday morning. Snow should taper off in the peaks of the
Transverse and Peninsular ranges by Saturday morning. Snow levels
are likely to be as low as 6,000ft with minor accumulations
possible around that elevation, but the heaviest snowfall is likely
to occur above 7,000ft where WPC probabilities show moderate-to-
high chances (50-80%) for snowfall totals >6" and even low-to-
moderate chances (30-50%) for localized amounts >12" in the peaks
of the San Bernadino mountains.


The probability of significant ice across the CONUS is less than
10 percent.


Mullinax




$$

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FOUS11 KWBC 200815
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
315 AM EST Thu Nov 20 2025

Valid 12Z Thu Nov 20 2025 - 12Z Sun Nov 23 2025

...Southern & Central Rockies...
Day 1...

An upper low over AZ this morning will take on an increasingly
negative tilt over northern Mexico though weaken overnight as it
mostly shears out to the east after 00Z. Snow will continue this
morning over northern AZ/NM into UT/CO with relatively high snow
levels >8000ft that will drop through the day. Some light snow will
still persist into D2 (early Friday) as lingering convergence and
upslope squeeze out another inch or two over the CO Rockies. WPC
probabilities for at least four inches of snow after 12Z Thu are
highest (>50%) over the highest peaks of the San Juans and the
Sangre de Cristos (generally above 10,000ft).

...California...
Days 1-2...

A Pacific upper low will form early this morning just west of
WA/OR and dive south-southeastward today through NorCal then to a
position west of Los Angeles early Friday. With regions of
vorticity rotating around the main center, bouts of snow will move
through the CA terrain from the Trinity/Siskiyou mountains today
then through the Sierra later this afternoon into Friday. Snow
levels will be around 5000-6000ft this morning over NorCal and
around 6000ft over the central/southern Sierra this evening and
slowly drop overnight. Over SoCal, snow levels will be around
6500ft this afternoon and drop to around 6000ft overnight. The
upper low will be in no hurry to exit the region, moving through
northern Baja California Saturday evening. By then, most of the
precipitation will be confined to the lower elevations and mostly
rain (though snow may linger over the SoCal mountains).

WPC probabilities for at least six inches of snow are >50% above
about 9000ft over the Sierra. Across the San Gabriel and San
Bernadino mountains, with a longer duration of precipitation
through Friday, significant snowfall is quite probable. WPC
probabilities for at least eight inches of snow are >50% above
about 7000ft (around the elevation of Big Bear Lake). Three-day
totals may exceed 12-18" above 9000ft. This could cause significant
travel disruptions over these higher elevations.

The probability of significant ice across the CONUS is less than
10 percent.

Fracasso

$$

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FOUS11 KWBC 201935
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
235 PM EST Thu Nov 20 2025

Valid 00Z Fri Nov 21 2025 - 00Z Mon Nov 24 2025

...Southern & Central Rockies...
Day 1...

An upper trough that is becoming negatively titled over New Mexico
today will weaken overnight as it shears out to the east after
00Z. Snow over northern AZ/NM into UT/CO, with relatively high snow
levels >8000ft, will still persist into early Friday as lingering
convergence and upslope muster up another inch or two of snow over
the CO/NM Rockies. WPC probabilities show low-to-moderate chances
(30-50%) for additional snowfall totals >4" in the San Juans, the
Sangre de Cristos, and central CO Rockies (generally above
10,000ft).

...California & Southern Rockies...
Days 1-3...

A Pacific upper low making its way south-southeastward through
northern CA today will become positioned of the southern CA coast
on Friday. As healthy PVA and upslope flow ensue down wind of the
upper low this afternoon, periods of snow will taper off over the Trinity/Siskiyou mountains and the persist along the Sierra Nevada.
Snow levels will hover around 6000ft over the central/southern
Sierra this evening and slowly drop overnight. Across southern CA,
snow levels around 6500ft this afternoon will drop to around
6000ft tonight. The upper low will continue to plunge southward
Friday night and become located west of Baja California by
Saturday. With the upper low so far south of the region, the colder temperatures aloft will be displaced south and diminished upslope
flow will reduce precipitation rates. This will make rain the
primary precipitation type across southern CA on Saturday (though
some snow may linger over the tallest peaks of the SoCal
mountains). The upper low will begin to push east on Sunday that
will deliver additional high elevation mountain snow to the San
Juans and Sangre De Cristo above 10,000ft.

WPC probabilities for >8" of snow are >50% above about 9000ft over
the Sierra. Across the San Gabriel and San Bernadino mountains,
with a longer duration of precipitation through Friday, a significant
heavy/wet snowfall is likely. WPC probabilities for >8" of snow
are >70% above 7000ft (around the elevation of Big Bear Lake).
Three-day totals may approach 24" above 9000ft. This could cause
locally significant travel disruptions over these higher
elevations, along with the potential for some tree damage and
infrastructure impacts given the heavy/wet consistency of the
snowfall. The WSSI does depict some Moderate to locally Major
Impacts in the San Gabriel and San Bernadino Mountains above
8,000ft. In the Southern Rockies, WPC probabilities show low-to-
moderate chances (30-50%) for snowfall totals >6" in the more
remote/higher ridge lines of the San Juans and Sangre De Cristo.


The probability of significant ice across the CONUS is less than
10 percent.


Mullinax




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FOUS11 KWBC 210718
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
218 AM EST Fri Nov 21 2025

Valid 12Z Fri Nov 21 2025 - 12Z Mon Nov 24 2025


...California & Southern Rockies...
Days 1-3...

A Pacific upper low near the central CA coast this morning will
continue to drop south-southeastward today into a position just
west of the northern Baja Peninsula by early Saturday. A
combination of healthy PVA, upslope flow, and a modest moisture
feed will promote periods of snow for the southern Sierra and SoCal
ranges today (San Rafael/San Gabriel/San Bernadino/San Jacinto).
Snow levels will continue to tick downward to between 5500-6000ft.
With the upper low so far south of the region by tomorrow, the
colder temperatures aloft will be displaced southward and
diminished upslope flow will reduce precipitation rates. Snow
levels will rise and change snow to rain below 7000ft before ending
midday Saturday. The upper low will begin to push eastward
Saturday night through Sunday and spread moisture across AZ into NM
and CO with snow at high elevations (generally above 8000-9000ft).
The upper low will pick up speed Sunday evening and lift through
CO and weaken into an open wave over the High Plains by early
Monday. Along and near its path, modest snow is expected over the
San Juans and Sangre de Cristos but snow levels will remain high
through the event (no lower than about 7500ft which will be at the
end of the event).

WPC probabilities for an additional 6 inches of snow today are

50% above about 10,000ft over the southern Sierra. Across the

SoCal Mountains, with a longer duration of precipitation today, a
significant heavy/wet snowfall is likely to continue. WPC
probabilities for an additional 6 inches of snow are >50% above
8000ft. This could cause locally significant travel disruptions
over these higher elevations, along with the potential for some
tree damage and infrastructure impacts given the heavy/wet
consistency of the snowfall. The WSSI does depict some Moderate to
locally Major Impacts in the San Gabriel and San Bernadino
Mountains above 8,000ft.

In the Southern Rockies, WPC probabilities for at least 8 inches
of snow primarily on Day 3 (Sunday) are >50% above about 11,000ft
in the more remote/higher ridge lines of the San Juans and
especially the Sangre De Cristo range.

...Pacific Northwest...
Day 3...

Quasi-zonal flow out of the Northern Pacific will bring in a
rather strong frontal system to WA/OR/ID and northwestern MT
Sunday. Snow levels around 5000-6000ft Sunday afternoon will drop
to below 3000ft by early Monday as precipitation lightens. Some
significant snow may impact the higher passes where WPC
probabilities for at least 6 inches of snow are >50% above about
4000-4500ft. Snow will also spread across northern ID into
northwestern MT late Sunday/early Monday with snow continuing
beyond this forecast period.

...Northeast...
Day 3...

A clipper system associated with a shortwave and dip in the jet
stream will push quickly through southern Ontario/Quebec and
northern NY/New England Sunday afternoon/evening. QPF amounts
appear light, and generally only an inch of two of snow is
expected. WPC probabilities for at least 4 inches of snow are less
than 10 percent, though the NBMexp (v5.0) probabilities max out
between 15-25% over the northern Green Mountains of VT.


The probability of significant ice across the CONUS is less than
10 percent.

Fracasso


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FOUS11 KWBC 211920
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
220 PM EST Fri Nov 21 2025

Valid 00Z Sat Nov 22 2025 - 00Z Tue Nov 25 2025


...Southern Rockies...
Days 2-3...

The upper-low that produced heavy mountain snow in the peaks of the
southern California mountains will make its way through northern
Mexico Saturday night. Healthy subtropical moisture will be
directed at the Southern Rockies at the same time as diffluent flow
aloft supports upper-level ascent atop the atmosphere. Add in the
favorable upslope component into mountain ranges such as the Gila
Mountains, the San Juans, and the Sangre De Cristo, and this
upper-low will produce snow in the Southern Rockies. Snow begins in
the AZ/NM mountains Saturday evening, then begins in far northern
NM and the CO Rockies on Sunday. Some lingering snow showers may
persist in the remote peaks of the Southern Rockies through early
Monday morning before concluding Monday afternoon.

Given the lack of a cold antecedent air-mass, snow levels will
struggle to dip much lower than 7,000ft. In terms of where the
heaviest snowfall is most likely to occur, elevations above 9,000ft
in the Mogollon Rim and Gila Mountains are most likely, while
heavy snow will be mostly confined to the more remote elevations
above 10,000ft in the San Juans and Sangre De Cristo. WPC
probabilities for at least 8 inches of snow primarily on Day 3
(Sunday) are >50% above about 11,000ft in the more remote/higher
ridge lines of the San Juans and especially the Sangre De Cristo
range. WPC probabilities show low-to-moderate chances (20-50%) for
storm total snowfall >8" for all the mountains and elevations
referenced, although the higher end of those probabilities applies
mostly to the highest and most remote sections of the Southern
Rockies.

...Pacific Northwest & Northern Rockies...
Days 2-3...

A Pacific disturbance embedded within uasi-zonal flow will usher in
a progressive, but potent, frontal system into WA/OR/ID and
northwestern MT Sunday. As the cold front traverses the Pacific
Northwest, snow levels around 5000-6000ft Sunday afternoon will
drop to as low as 2,000ft on the windward side of the Cascades by
early Monday as precipitation begins to taper off. WPC
probabilities for >4" of snow do range between 30-50% in both
Stevens and Snoqualmie Passes, with potentially upwards of 6"
possible. Snow will also spread across northern ID into
northwestern MT late Sunday and through Monday as moisture
associated with the Pacific system moves through. Additional heavy
snowfall may ensue along the Lewis Range on Monday as strengthening
high pressure to the north gives rise to strengthening easterly
upslope flow. WPC probabilities show moderate-to-high chances
(50-80%) for snowfall totals >8" in the Lewis Range through Monday
afternoon. The highest elevations of the Lewis Range may top 12"
in spots through Monday afternoon.

...Northeast...
Days 2-3...

A clipper system rotating beneath the base of an broad upper-low
over Quebec will push quickly through northern NY/New England
Sunday evening and exit the to the east by Monday morning. Guidance
shows some uncertainty on the strength of the approaching clipper
system with the GFS/CMC showing a more amplified solution while the
ECMWF/UKMET camp is less amplified and features less QPF. Even
taking the average of these solutions, it would lead to some minor
snowfall accumulations (1-4") across the Tug Hill, the
Adirondacks, and both the Green and White Mountains. At this
moment, WPC probabilities show low-to-moderate chances (20-50%) for
snowfall totals >4" in these ranges with elevations above 2,000ft
most favored for accumulating snowfall.


The probability of significant ice across the CONUS is less than
10 percent.

Mullinax





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FOUS11 KWBC 220732
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
232 AM EST Sat Nov 22 2025

Valid 12Z Sat Nov 22 2025 - 12Z Tue Nov 25 2025


...Southern Rockies...
Days 1-2.5...

An upper-low just west of Baja California will move eastward today
and northeastward tonight, spreading rain and high mountain snow
across AZ then into CO/NM tomorrow. Healthy subtropical moisture
will be directed at the Southern Rockies at the same time as
diffluent flow aloft supports upper-level ascent atop the
atmosphere. Upslope enhancement into some of the mountain ranges
such as the Gila Mountains, the San Juans, and the Sangre De Cristo
will aid in producing modest snow totals for the mountain peaks.
The upper low will cross over the Four Corners region and bring
heavier snow to the San Juans and Sangre de Cristos, but at high
elevations. Snow will taper off on Monday as the upper low slowly
fills.

Given the lack of a cold antecedent air-mass, snow levels will
struggle to dip much lower than 7,000ft. Elevations above 9,000ft
in the Mogollon Rim and Gila Mountains and the more remote
elevations above 10,000ft in the San Juans and Sangre De Cristos
will see the heaviest snow. WPC probabilities for at least 8 inches
of snow are >50% above about 11,000ft in the more remote/higher
ridge lines of the San Juans and Sangre De Cristo range. WPC
probabilities are low-to-moderate (20-50%) for storm total snowfall

8" over the White Mountains in eastern AZ.

...Pacific Northwest & Northern Rockies...
Days 1-3...

A Pacific disturbance embedded within quasi-zonal flow will usher
in a progressive, but potent, frontal system into WA/OR/ID and
northwestern MT Sunday. As the cold front traverses the Pacific
Northwest, snow levels around 5000-6000ft Sunday afternoon will
drop to as low as 2,000ft on the windward side of the Cascades by
early Monday as precipitation begins to taper off. WPC
probabilities for >4" of snow do range between 30-60% in both
Stevens and Snoqualmie Passes, with potentially upwards of 6"
possible.

Snow will also spread across northern ID into northwestern MT late
Sunday and through Monday as moisture associated with the Pacific
system moves through. Additional heavy snowfall along the Lewis
Range on Monday may be enhanced by easterly upslope flow due to
strengthening high pressure to the north. WPC probabilities for at
least 8 inches of snow are >50% across the Lewis Range and above
7000ft where more than a foot of snow is possible at the highest
elevations.

...Northeast...
Day 2...

A clipper system rotating beneath the base of an broad upper-low
over Quebec will push quickly through northern NY/New England
Sunday afternoon/evening and exit to the east by Monday morning.
QPF and therefore snowfall may be somewhat limited due to its fast
movement, but some upslope enhancement may yield a bit more than
2-3" of snow across the Tug Hill, Adirondacks, and both the Green
and northern White Mountains. WPC probabilities for at least 4
inches of snow are low (10-40%) in these areas generally above
15000-2000ft.


The probability of significant ice across the CONUS is less than
10 percent.

Fracasso/Mullinax


$$

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FOUS11 KWBC 221903
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
203 PM EST Sat Nov 22 2025

Valid 00Z Sun Nov 23 2025 - 00Z Wed Nov 26 2025


...Southern Rockies...
Days 1-2...

An upper-low over Baja California will move northeast today and
tonight, spreading rain and high mountain snow across AZ then into
CO/NM tomorrow. Healthy subtropical moisture directed at the
Southern Rockies will at the same time be co-located beneath
diffluent flow aloft. Upslope enhancement into some of the
mountain ranges such as the Gila Mountains, the San Juans, and the
Sangre De Cristo will aid in producing periods of moderate-to-heavy
snow across these mountain ranges. The upper low will cross over
the Four Corners region on Sunday and deliver heavier snowfall to
the San Juans and Sangre de Cristos, but primarily in the
higher/remote elevations. Snow tapers off by Monday as the upper
low tracks into the central Great Plains.

Due to the lack of a cold antecedent air-mass, snow levels will
struggle to fall much lower than 7,000ft. Elevations above 9,000ft
in the Mogollon Rim and Gila Mountains and the more remote
elevations above 10,000ft in the San Juans and Sangre De Cristos
are the most likely candidates to see the heaviest snowfall amounts.
WPC probabilities for at least 8 inches of snow are >50% above
about 11,000ft in the more remote/higher ridge lines of the San
Juans and Sangre De Cristo range.

...Pacific Northwest & Northern Rockies...
Days 1-3...

A Pacific disturbance embedded within quasi-zonal flow will usher
in a progressive, but potent, frontal system into WA/OR/ID and
northwestern MT Sunday. As the cold front traverses the Pacific
Northwest, snow levels around 5000-6000ft Sunday afternoon will
drop to as low as 2,000ft on the windward side of the Cascades by
early Monday as precipitation begins to taper off. WPC
probabilities for >4" of snow do range between 40-60% in both
Stevens and Snoqualmie Passes, with potentially upwards of 6"
possible. A brief lull in mountain snow Monday night and into
Tuesday morning concludes by Tuesday afternoon when the next
Pacific storm system delivers another round of mountain snow to
the Cascades and Olympics with snow levels as low as 2,500ft.
Additional snowfall totals of 1-4" are possible through Tuesday
afternoon with more snow still to come into the middle of the week.

Farther east, snow will also spread across northern ID into
western MT late Sunday and through Monday as moisture associated
with the Pacific system passes through. Minor snowfall
accumulations (1-4") are possible as far south as the Tetons and
Big Horns. The focus for the heaviest snowfall resides along the
Lewis Range on Monday as snowfall rates become enhanced by
easterly upslope flow due to strengthening high pressure over
southwest Canada. Snow should taper off across all of the northern
Rockies by Early Tuesday morning. WPC probabilities for >8" of
snowfall are >70% across the Lewis Range above 5,000ft. In the
highest elevations of the Lewis Range (>6,000ft), WPC probabilities
show moderate chances (40-70%) for snowfall totals >12". The WSSI
does show mostly Minor Impacts in the Lewis Range, the Bitterroots,
the Crazy Mountains with some localized Moderate Impacts (hazardous
driving conditions) in the higher peaks of the Lewis Range.

...Northeast...
Day 2...

A clipper system rotating beneath the base of an broad upper-low
over Quebec will push quickly through northern NY/New England
Sunday afternoon/evening and exit to the east by Monday morning.
QPF and the resulting snowfall will be somewhat limited due to its
fast movement and the clipper being relatively moisture-starved,
but some upslope enhancement may allow for anywhere between 1-4"
of snow across the Tug Hill, Adirondacks, and both the Green and
northern White Mountains. WPC probabilities for at least 4 inches
of snow remain on the lower side (10-40%) in these areas generally
above 1500-2000ft in the Adirondacks and Tug Hill. Still, some
snow covered roads could make for slippery driving conditions
Sunday night and Monday morning.

...Northern Plains...
Day 3...

The shortwave trough responsible for the snow across the Northern
Rockies to start the week moves into the northern High Plains on
Monday night. There are ongoing differences on model guidance in
terms of the speed/strength of this feature as it enters the
northern High Plains. Most guidance does agree, however, that as
the 500mb trough tracks over the Dakotas, a compact 500mb low
develops and with an inverted low-to-mid level trough on the low's
western flank. This becomes effectively a TROWAL that helps to
focus a narrow band of 850-700mb FGEN and WAA that, when combined
with sufficient lef-texit region jet streak dynamics, gives rise to
a band of moderate-to-heavy snow starting over eastern MT Monday
night. As the 500mb low forms over the Dakotas on Tuesday, EC-AIFS
shows the TROWAL develops a formidable band of heavy snow over the
Dakotas Tuesday morning that then tracks into central MN by
Tuesday afternoon.

It is worth noting guidance over the last 12-24 hours is still
trying to synthesize a better forecast track with this developing
storm system, and the placement of where the heavier snowfall
occurs is still coming into focus. This is also looking like a
fairly progressive system, but could still pack a punch with
snowfall rates >1"/hr in play as it tracks through the northern
High Plains and Upper Midwest through Tuesday night. At this
moment, WPC probabilities are focusing on ND (20-50% chances for

4" of snow) as the most likely to witness impactful snowfall, as

well as gusty winds that greatly reduce visibilities. Heavy snow
will likely translate into northern MN by Tuesday evening, and SD
could also contend with wind blown snow that causes travel delays.
Interests in the Northern Plains and Upper Midwest should keep a
close eye on the forecasts from their NWS WFOs and WPC in the
coming days given this storm could prove a headache for those
traveling in the lead up to Thanksgiving.


The probability of significant ice across the CONUS is less than
10 percent.

Mullinax





$$

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FOUS11 KWBC 230758
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
258 AM EST Sun Nov 23 2025

Valid 12Z Sun Nov 23 2025 - 12Z Wed Nov 26 2025


...Southern Rockies...
Day 1...

An upper-low over central AZ this morning will move across the
Four Corners and through Colorado later today. Diffluent flow atop
a robust subtropical moisture feed will promote snow across the San
Juans and Sangre de Cristos, aided by upslope enhancement as the
upper low approaches. Snow levels will be high -- generally above
9000ft initially then dropping to around 7000ft as precipitation
ends early Monday. WPC probabilities for at least 8 inches of snow
are >50% above about 11,000ft in the more remote/higher ridge lines
of the San Juans and Sangre De Cristo range.

...Pacific Northwest & Northern Rockies...
Days 1-2...

A Pacific disturbance embedded within quasi-zonal flow will usher
in a progressive, but potent, frontal system into WA/OR/ID and
northwestern MT this morning. As the cold front traverses the
Pacific Northwest, snow levels around 5000-6000ft this afternoon
will drop to as low as 2,000ft on the windward side of the Cascades
by early Monday as precipitation begins to taper off. This would
affect many of the passes with at least some snow, and WPC
probabilities for >4" of snow are between 30-50% in both Stevens
and Snoqualmie Passes.

Farther east, snow will also spread across northern ID into
western MT later today through Monday as moisture associated with
the Pacific system passes through. Minor snowfall accumulations
(1-4") are possible as far south as the Tetons and Big Horns. The
focus for the heaviest snowfall resides along the Lewis Range on
Monday as snowfall rates become enhanced by easterly upslope flow
due to strengthening high pressure over southwest Canada. Snowfall
rates nearing >1"/hr are possible at higher open passes (e.g.,
Marias Pass). Snow should taper off across all of the northern
Rockies by early Tuesday morning. WPC probabilities for >8" of
snowfall are >70% across the Lewis Range above 5,000ft. In the
highest elevations of the Lewis Range (>6,000ft), WPC probabilities
show moderate chances (40-70%) for snowfall totals >12". The WSSI
does show mostly Minor Impacts in the Lewis Range, the Bitterroots,
and the Crazy Mountains.

...Northern Cascades/Olympic Peninsula...
Day 3...

The next Pacific system will move into western Washington on
Tuesday on a 120kt jet. Cold air in place could support some spotty
freezing rain along/east of the crest as warmer air aloft moves
in. Snow levels will slowly rise as the warm front lifts through
overnight into early Wednesday, but may be loathe to budge east of
the Cascades until later on Wednesday. With a fairly long moisture
fetch into the Pacific, precipitation amounts could be at least
modest, suggesting impactful snow even at Snoqualmie Pass. Through
12Z Wednesday, WPC probabilities of at least 6 inches of snow are

50% above about 5000ft.

...Northeast...
Day 1...

A clipper system rotating beneath the base of an broad upper-low
over Quebec will push quickly through northern NY/New England this afternoon/evening and exit to the east by Monday morning. QPF and
the resulting snowfall will be somewhat limited due to its fast
movement and the clipper being relatively moisture-starved, but
some upslope enhancement may allow for anywhere between 1-4" of
snow across the Tug Hill, Adirondacks, and the Green and northern
White Mountains. WPC probabilities for at least 4 inches of snow
remain on the lower side (10-40%) in these areas generally above
1500-2000ft in the Adirondacks and Tug Hill, with the highest peaks
showing a slightly higher change (50-60%) of at least 4 inches of
snow. Still, some snow covered roads could make for slippery
driving conditions tonight and Monday morning.


...Northern Plains...
Day 3...

The shortwave trough responsible for the snow across the Northern
Rockies to start the week moves into the northern High Plains on
Monday night. By early Tuesday, a sharpening of the jet will allow
the mid-level shortwave to deepen and close off (at least briefly)
as it remains progressive. WAA and lower-level FGEN will support a
stripe of light to modest snow across ND as a surface low deepens
along the ND/SD border. It will then continue to strengthen and
lift northeastward through MN into the western Great Lakes, with
sufficiently cold air on its northwest side for a broad area of
snow. The wrapped-up system could form a TROWAL across northern MN,
favoring a region of heavier snow. The models disagree on the
location and amount of QPF (and thus snow), but the potential
exists for an axis of appreciable snow late Tuesday into Wednesday
(and beyond for the western Great Lakes).

Through 12Z Wednesday, WPC probabilities for at least 4 inches of
snow are >50% from northeastern MT across much of ND and northern
MN. Within this region, probabilities for at least 8 inches of snow
are 30-50% over central ND and northern to northeastern MN.
Blowing snow may become a hazard as winds increase in response to
the deepening low pressure. Interests in the Northern Plains and
Upper Midwest should keep a close eye on the forecasts from their
NWS WFOs and WPC in the coming days given this storm could prove a
headache for those traveling in the lead up to Thanksgiving.


The probability of significant ice across the CONUS is less than
10 percent.

Fracasso/Mullinax


$$

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FOUS11 KWBC 231947
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
247 PM EST Sun Nov 23 2025

Valid 00Z Mon Nov 24 2025 - 00Z Thu Nov 27 2025


...Pacific Northwest & Northern Rockies...
Days 1-2...

A Pacific shortwave trough is escorting a progressive, but potent,
frontal system into WA/OR/ID and northwestern MT today. As the
cold front traverses the Pacific Northwest, snow levels around
5000-6000ft this afternoon will drop to as low as 2,000ft on the
windward side of the Cascades tonight as precipitation. Even as the
upper-level trough exits east, lingering upslope flow could keep
light snow in the forecast through Monday afternoon. This would
affect many of the passes with at least some snow, and WPC
probabilities for >4" of snow are between 30-50% in both Stevens
and Snoqualmie Passes.

Farther east, as the aforementioned plume of mid-level moisture
tracks eastward, snow will also spread across northern ID into
western MT this afternoon through Monday as moisture associated
with the Pacific system passes through. Measurable snowfall will
stretch as far south as the Tetons and Absaroka with the peaks of
the Tetons north of Jackson, WY sporting moderate-to-high chances
(50-70%) for snowfall totals >8". The focus for the heaviest
snowfall resides along the Lewis Range tonight and through Monday
as snowfall rates become enhanced by easterly upslope flow due to
strengthening high pressure over southwest Canada. Snowfall rates

1"/hr are possible at higher open passes (including Marias Pass).

Snow should taper off across all of the northern Rockies by early
Tuesday morning. WPC probabilities for >8" of snowfall are >70%
across the Lewis Range above 5,000ft. In the highest elevations of
the Lewis Range (>6,000ft), WPC probabilities show moderate chances
(40-70%) for snowfall totals >12". The WSSI does show Moderate
Impacts (hazardous travel conditions) in the Lewis Range, the
Bitterroots, the Crazy Mountains, and peaks of the MT Absaroka.

...Northern Cascades/Olympic Peninsula...
Days 2.5-3...

Following a brief lull in the action on Monday night and Tuesday
morning, the next Pacific system moves into western WA on Tuesday
at the nose of an 140kt 250mb jet. Unlike the storm system this
weekend, Canadian high pressure will provide a colder air-mass out
ahead of this next Pacific storm system that will support some
spotty freezing rain along the leeward slopes/valleys of the
Cascades and in the valleys of the Columbia River Basin over
northern WA. Snow levels will gradually rise as the warm front
lifts through Tuesday night into early Wednesday, but the surface
front will takes longer to cross the Cascades rather than the more
robust 700mb WAA nose that support the potential for icy
conditions east of the Cascades. Thanks to a longwave trough firmly
entrenched over the North Pacific, an extended moisture fetch into
the the Pacific Northwest provides a favorable setup for multiple
days worth of accumulating snow and ice that continues through
Wednesday afternoon. Through 00Z Thursday, WPC probabilities of at
least 6 inches of snow are >50% above about 4000ft, with as much as
4-6" of snowfall possible near Snoqualmie Pass.

...Northeast...
Day 1...

A clipper system rotating beneath the base of an broad upper-low
over Quebec will push quickly through northern NY/New England this
evening and exit to the east by Monday morning. QPF and the
resulting snowfall will be somewhat limited due to its fast
movement and the clipper being relatively moisture-starved, but
upslope enhancement will allow for anywhere between 1-4" of snow
across the Tug Hill, Adirondacks, and the Green and northern White
Mountains. WPC probabilities for at least 4 inches of snow remain
on the lower side (10-30%) in these areas generally above
1500-2000ft in the Adirondacks and Tug Hill. Despite the minor
accumulations, this system would still support snow covered roads
that could make for slippery driving conditions tonight and Monday
morning.

...Northern Plains & Upper Midwest...
Days 2-3...

The shortwave trough responsible for the snow across the Northern
Rockies to start the week moves into the northern High Plains by
Monday night. An 850mb low will form along a strengthening
925-850mb front over central ND, while a narrow inverted trough
axis forms on its western flank. By 12Z Tuesday, areas from
northeast MT to central ND will be enveloped in a band of
moderate-to-heavy snow that also includes increasingly gusty winds
as low pressure strengthens. As the low moves east, the TROWAL on
the western flank of the storm is likely to produce at least 1"/hr
snowfall rates during the daytime hours Tuesday, which combined
with wind gusts approaching 30 mph will cause poor visibility.
However, areas not beneath the deformation axis will struggle to
accumulate given marginal boundary layer temperatures and lesser
SLRs. Expect a tight gradient in snowfall totals, where beneath the
TROWAL WPC probabilities over central ND show low-to- moderate
chances (30-50%) for snowfall totals >6" through Tuesday evening.
Across northeast ND and southern ND, those probabilities drop to
low chances (10-30%) for >6".

By Tuesday evening, the winter storm will strengthen as most
guidance agrees that a closed 500 low develops as it heads for
central MN. The 500mb low will be embedded within a broad 500mb
trough that takes on a negative tilt, fur The heaviest snowfall is
likely to occur just north of the 700mb low track, which places
northern MN in the sweet spot for heavier totals. Beneath the
strengthening TROWAL, snowfall rates of 1-2"/hr are possible late
Tuesday afternoon and into Tuesday night. As the storm tracks into
northern WI Tuesday night, ENErly winds will accelerate off Lake
Superior and introduce more low-level moisture and convergence over
the MN Arrowhead. Snowfall rates of 1-2"/hr are anticipated and
should accumulate efficiently do the bulk of the snow in northern
MN coming over night. Snow will also fall heavily over northwest WI
and the western Michigan U.P. Tuesday night and continue into
Wednesday as CAA over Lake Superior kick up lake-enhanced snowfall.

WPC probabilities for >6" of snow are >50% across north-central MN
with low-to-moderate chance probabilities (30-50%) for >12" of
snowfall in the MN Arrowhead. The area most likely to see >12"
snowfall amounts are portions of Michigan's far western U.P.,
including the Porcupine Mountains, where WPC probabilities show
moderate chances (40-60%) for >12" of snowfall. Across much of ND,
most snowfall amounts will range between 2-6", but on which end of
those amounts portions of the state witness will depend heavily on
the placement of the banded areas of snowfall. Interests in the
Northern Plains and Upper Midwest should keep a close eye on the
forecasts from their NWS WFOs and WPC in the coming days given this
storm could prove a headache for those traveling in the lead up to Thanksgiving.


The probability of significant ice across the CONUS is less than
10 percent.

Mullinax





$$

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FOUS11 KWBC 240813
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
313 AM EST Mon Nov 24 2025

Valid 12Z Mon Nov 24 2025 - 12Z Thu Nov 27 2025


...Northern Rockies...
Day 1...

Shortwave over Washington this morning will carry a cold front
through the Northern Rockies today. The strongest height falls will
cross through northwestern MT around Glacier NP with modest snow
above 5000-6000ft. WIth the moisture feed stretched back (but
weakening) to the Pacific, snow will fall as far south as the
Bitterroots and into northwestern WY where amounts will be lower (a
few inches). Snow will taper from west to east this afternoon
through this evening as the cold front makes steady progress
through the region. WPC probabilities for at least 8 inches of snow
are >50% above about 5000ft.


...Pacific Northwest/Northern Rockies...
Days 2-3...

The next Pacific system moves into western WA on Tuesday at the
nose of an 140kt 250mb jet. Colder air in place ahead of the
moisture may support some spotty freezing rain along the leeward
slopes/valleys of the Cascades and in the valleys of the Columbia
River Basin over northern WA. Snow levels will gradually rise as
the warm front lifts through Tuesday night into early Wednesday,
but the surface front will takes longer to cross the Cascades
rather than the more robust 700mb WAA nose that support the
potential for icy conditions east of the Cascades. Thanks to a
longwave trough firmly entrenched over the North Pacific, an
extended moisture fetch into the the Pacific Northwest will support
a more or less continuous stretch of mountain snow over the
Cascades and downstream into the Northern Rockies through the end
of this forecast period (then continuing into the medium range).
Snow levels will vary, starting around 2000-4000ft then rising to
around 5000-7000ft as milder air moves in. WPC probabilities for at
least 8 inches of snow are >50% above about 5000ft. Both
Snoqualmie and Stevens Pass may see multiple inches of snow before
snow levels rise above the passes early Wednesday.

...Northern Plains/Upper Midwest/Upper Great Lakes...
Days 1-3...

The shortwave trough exiting the Northern Rockies this afternoon
will move into the northern High Plains tonight. The upper jet
across the US/Canada will sharpen and support a strengthening area
of low pressure that will move from the Plains to the Upper Midwest
and western Great Lakes over the next few days. Tonight, an 850mb
low will form along a strengthening 925-850mb front over central
ND, while a narrow inverted trough axis forms on its western flank.
By 12Z Tuesday, bands of moderate to heavy snow are likely from
northeastern MT to central ND with increasingly gusty winds as the
low pressure strengthens. Tuesday afternoon the low over
southeastern MN will start to deepen quickly as the mid-level
shortwave starts to close off, allowing a TROWAL to form on the
western side of the storm. This could allow for >1"/hr snowfall
rates along with gusty winds over 30mph, causing blowing/drifting
snow. Some areas closer to Lake Superior and over central MN will
see marginal temperatures and snow may not accumulate quickly if
the rates are not high, though colder air will eventually win and
change all areas to snow overnight into early Wednesday as the low
moves into the U.P. of Michigan and deepens into the mid 990s mb.
By Wednesday night into early Thursday, the system will reach its
peak intensity over Ontario and take the bulk of its snow with it.
However, northerly to northwesterly flow will transition the lake-
enhanced snow to lake effect snow over northern WI into the U.P.
where the 850-lake temperature difference will be >15C (-10 to -14C
at 850mb and a lake temperature around 5C). Lake effect snow will
eventually break out across the rest of the Great Lakes by Thursday
morning and continue into the medium range period.

WPC probabilities for at least 4 inches of snow are >50% from
northwestern ND to central MN then eastward through the Arrowhead,
northern WI, and across much of the U.P. of Michigan. Within this
areas, probabilities for at least 8 inches of snow are >50% over
northeastern MN due to the synoptic system itself. Across northern
WI and into the U.P., the combination of synoptic snow and then
lake effect snow will boost totals well over a foot. There, WPC
probabilities for at least 18 inches of snow are >50% from near
Ironwood northeastward across the northern portion of the U.P. near
the Huron Mountains.

The probability of significant ice across the CONUS is less than
10 percent.

Fracasso

$$

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FOUS11 KWBC 241905
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
205 PM EST Mon Nov 24 2025

Valid 00Z Tue Nov 25 2025 - 00Z Fri Nov 28 2025


...Significant winter storm to impact parts of the Northern Plains
and Upper Midwest/Great Lakes through Wednesday before lake effect
snow intensifies on Thanksgiving. Key Messages have been issued for
this storm...


...Northern Plains/Upper Midwest/Upper Great Lakes...
Days 1-3...

Shortwave trough exiting the Northern Rockies this afternoon will=20
move into the northern High Plains tonight. The upper jet across=20
the US/Canada will sharpen and support a strengthening area of low=20
pressure that will move from the Plains to the Upper Midwest and=20
western Great Lakes over the next few days. Tonight, an 850mb low=20
will form along a strengthening 925-850mb front over central ND,=20
while a narrow inverted trough axis forms on its western flank. By=20
12Z Tuesday, bands of moderate to heavy snow are likely from=20
northeastern MT to central ND with increasingly gusty winds as the=20
low pressure strengthens. Tuesday afternoon the low over=20
southeastern MN will start to deepen even more rapidly as the mid-
level shortwave starts to close off, allowing a TROWAL to form on=20
the western side of the storm. This could allow for >1"/hr snowfall
rates along with gusty winds over 30mph, causing some blowing/drifting
snow. Some areas closer to Lake Superior and over central MN will=20
see marginal temperatures and snow may not accumulate quickly if=20
the rates are not high, though colder air will eventually win and=20
change all areas to snow overnight into early Wednesday as the low=20
moves into the U.P. of Michigan and deepens into the mid 990s mb.
There remains some latitudinal uncertainty with today's guidance
shifting slightly south across the ND/MN and aligned with the
second ensemble cluster in WPC's QPF cluster prototype in the
north-central U.S.. Mesoscale banding within the inverted trough
and eventual TROWAL will likely make for rapidly changing
conditions within narrow corridors of heavy snow.

By Wednesday night into early Thursday, the system will reach its=20
peak intensity over Ontario and take the bulk of its snow with it.=20
However, northerly to northwesterly flow will transition the lake-=20
enhanced snow to lake effect snow over northern WI into the U.P.=20
where the 850-lake temperature difference will be >15C (-10 to
-14C at 850mb and a lake temperature around 5C). Lake effect snow=20
will eventually break out across the rest of the Great Lakes by=20
Thursday morning and continue into the medium range period.=20

WPC probabilities for at least 8 inches of snow are 30-50% from=20
northwestern ND to central MN. Then, these probs increase to 50-70%
across northeast MN and the MN Arrowhead. Across northern WI and=20
into the U.P., the combination of synoptic snow and then lake=20
effect snow will boost totals well over a foot. There, WPC=20
probabilities for at least 24 inches of snow are 50-80% from near=20
Ironwood northeastward across the northern portion of the U.P. near
the Huron Mountains. This region is also where major impacts due to
snow amounts are possible. Residents and visitors in the Upper
Midwest/Great Lakes are advised to check the latest forecast=20
before traveling this week.


...Great Lakes...
Day 3...

Lake effect snow will continue on day 3 (00z 11/27-00z 11/28) as
the deep low drifts into southeast Canada and promotes strong west-northwesterly flow over the relatively warm lake waters. Fetch
will be favorable for additional snow across the U.P. of MI and the
northern L.P., as well as along the shores of Lake Erie from
northwest PA to western NY as well as the Tug Hill of NY downwind
of Lake Ontario. Current WPC probabilities for at least 8 inches of
snow on day 3 are 60-80% for these locations.

...Pacific Northwest/Northern Rockies...
Days 1-3...

The next Pacific system moves into western WA on Tuesday at the=20
nose of an 140kt 250mb jet. Colder air in place ahead of the=20
moisture may support some spotty freezing rain along the leeward=20 slopes/valleys of the Cascades and in the valleys of the Columbia=20
River Basin over northern WA. Snow levels will gradually rise as=20
the warm front lifts through Tuesday night into early Wednesday,=20
but the surface front will takes longer to cross the Cascades=20
rather than the more robust 700mb WAA nose that support the=20
potential for icy conditions east of the Cascades. Thanks to a=20
longwave trough firmly entrenched over the North Pacific, an=20
extended moisture fetch into the the Pacific Northwest will support
a more or less continuous stretch of mountain snow over the=20
Cascades and downstream into the Northern Rockies through the end=20
of this forecast period (then continuing into the medium range).=20
Snow levels will vary, starting around 2000-4000ft then rising to=20
around 5000-7000ft as milder air moves in ahead of a potent low
pressure system on Thursday. WPC probabilities for at least 8=20
inches of snow are >50% above about 5000ft. Both Snoqualmie and=20
Stevens Pass may see multiple inches of snow before snow levels=20
rise above the passes early Wednesday.


The probability of significant ice across the CONUS is less than=20
10 percent.

Snell


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!_60s3P1rZA2qOM-sH8hmxQmMcm_TMHKSclFZitwZibDbR= 9U43WW4a4OnOF9smZ5yJhTQx51PqToOcrM8C9y7zFDOnTw$=20



$$

=3D =3D =3D
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FOUS11 KWBC 250750
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
250 AM EST Tue Nov 25 2025

Valid 12Z Tue Nov 25 2025 - 12Z Fri Nov 28 2025


...Significant winter storm to impact parts of the Northern Plains
and Upper Midwest/Great Lakes through Wednesday before lake effect
snow intensifies on Thanksgiving. Key Messages have been issued=20
for this storm...


...Northern Plains/Upper Midwest/Great Lakes...
Days 1-3...

Shortwave trough moving through the northern Plains this morning=20
will continue eastward today. The sharpening upper jet across the=20
US/Canada supports a strengthening area of low pressure that will=20
move from the Plains to the Upper Midwest and western Great Lakes=20
over the next couple of days. An inverted trough over ND will act=20
as a focus for modest snow this morning, then translate east-
southeastward today as the surface low deepens over southeastern=20
MN. Trend in recent guidance was to bring this swath of light to=20
moderate snow farther south than just 12hrs ago, down the I-94=20
corridor into the Twin Cities. As the mid- level shortwave starts=20
to then close off, a TROWAL should form on the western side of the=20
storm as warmer air wraps northward and westward around the low.=20
This could allow for >1"/hr snowfall rates along with gusty winds=20
over 30mph, causing some blowing/drifting snow and low visibility=20
at times. By tonight into early Wednesday, the low will lift toward
the U.P. with northeasterly flow off Lake Superior, aiding in=20
enhancing moisture into the region just north of the 850mb low=20
(eastern central MN into northern WI).=20

By Wednesday night into early Thursday, the system will reach its=20
peak intensity over Ontario and take the bulk of its snow with it.=20
However, northerly to northwesterly flow will transition the lake-=20
enhanced snow to lake effect snow over northern WI into the U.P.=20
where the 850-lake temperature difference will be >15C (-10 to
-14C at 850mb and a lake temperature around 5C). Lake effect snow=20
will eventually break out across the rest of the Great Lakes by=20
Thursday morning and continue through the day and into Friday=20
morning. With 850mb temperatures < -10C and Lakes Erie/Ontario=20
SSTs around +10C, intense lake bands will persist on WSW to W to=20
WNW flow as the cyclone pulls farther away from the region. Single
banded snow will drop southward and become more multi-banded=20
downwind of Lake Erie but may retain a stronger single band off=20
Lake Ontario. Multi-banded snow will persist across the Upper=20
Great Lakes as well through early Friday.=20

For the synoptic event D1, WPC probabilities for at least 6 inches
of snow are >30% from southeastern ND and northeastern SD eastward
across much of central MN from the Twin Cities northward to the=20
Arrowhead. Higher probabilities >70% exist across central MN and=20
northern WI to the U.P. of Michigan. After the surface low passes=20
and the snow becomes driven by lake effect (mostly D2-3), WPC=20
probabilities for at least 12 inches of snow are >50% from near=20
Ironwood eastward across the northern portion of the U.P. near the=20
Huron Mountains. This region is also where major impacts due to=20
snow amounts are possible as three day snow totals could be in=20
excess of two feet. Over northwestern Lower Michigan, lake effect=20
snow could yield in excess of a foot of snow as well (probabilities
are >50% just east of Traverse City). Residents and visitors in=20
the Upper Midwest/Great Lakes are advised to check the latest=20
forecast before traveling this week.

Lake effect snow will pick up in earnest over western and northern
NYS on Thursday (Thanksgiving) and continue into Friday. WPC=20
probabilities for at least 8 inches of snow are >70% over=20
northeastern OH, northwestern PA, and western NY as well as the Tug
Hill Plateau downwind of Lake Ontario. Areas that see stronger=20
snow bands hold the longest may see totals in excess of 18 inches,=20 especially over northwestern PA where WPC probabilities are already

50%.=20

...Pacific Northwest/Northern Rockies...
Days 1-3...

An active North Pacific jet will send in two systems into the=20
Pacific Northwest and northern Rockies over the next three days.=20
The first will be today as the upper jet dips south across=20
Washington and a cold front (with a leading warm front) move in=20
from the west/southwest. Another system will form west of 140W=20
tomorrow and travel along the lead stationary/moisture boundary=20
into Washington on Thursday. Snow levels will start low today with=20
colder air in place but then rise on Wednesday as milder air wins=20
out across the region. The second system will push into the Rockies
late Thurs/early Fri.

For D1, colder sheltered locations along/east of the Cascades may=20
see some freezing rain as moisture moves in from the west.=20
Otherwise, snow levels initially near 2000-4000ft (north to south)=20
along the Cascades will slowly rise over the northern WA Cascades=20
but rise much quicker over the southern WA/northern OR Cascades to=20
over 6000ft by early Wednesday. Thereafter, snow levels will rise=20
well above 5000-6000ft Thursday as the second system moves in. WPC=20 probabilities of at least 6 inches of snow D1 are >50% above about=20 3000-4000ft in the WA Cascades (which includes Stevens and=20
Snoqualmie Passes). For D2-3, WPC probabilities for at least 8=20
inches of snow are >50% above about 5000ft. Farther east, much of=20 northwestern MT above 6000ft or so across the Lewis and Flathead=20
Ranges show probabilities of at least 8 inches of snow above 50%.


The probability of significant ice across the CONUS is less than=20
10 percent.

Fracasso

...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!4LDjCV1VJ-Jt_mbQyvEw7p95f8ihrIq4NbocPm8O4o_KN= 9w-OXp-MvmkFlPWbEc22b1dUNJdhbzUHBf4SUOwBb9sSDw$=20



$$

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FOUS11 KWBC 252111
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
411 PM EST Tue Nov 25 2025

Valid 00Z Wed Nov 26 2025 - 00Z Sat Nov 29 2025


...Significant winter storm/locally a Blizzard continues to impact
parts of the Upper Midwest/Great Lakes through Wednesday before=20
lake effect snow intensifies Wednesday night and lingers through=20 Thanksgiving and even Friday for the eastern Great Lakes...

...Confidence increasing on a second winter storm to affect the
Northern Plains Friday and the Midwest/Great Lakes Friday night=20
into Sunday...

...Key Messages for both systems are in effect and linked below...


...Upper Midwest/Great Lakes...=20
Days 1-3...

Potent developing low over eastern South Dakota this afternoon will
continue to deepen/strengthen as it tracks east over Wisconsin
tonight and the northern L.P. of Michigan Wednesday. The trough
around this low takes on a negative tilt tonight as the downstream
SWly jet intensifies and a strong pressure gradient with a 1032mb
high over ND by Wednesday morning allows for a strong and broad
wind field that will allow Blizzard conditions as indicated by the
Blizzard Warnings over the U.P. of MI and in northeast SD. A=20
TROWAL forms on the western side of the storm as warmer air wraps=20
northward and westward around the low which aids dynamic banding,
but also results in a more marginal thermal environment tonight
over the eastern U.P. and Wednesday over the northern L.P. However,
areas on the back side of the low will see rapid cooling that
allows for heavy snow banding and eventually LES.=20

The system continues to strengthen/deepen through Thursday night as
it pushes in to Quebec and becomes rather sprawling. Powerful northerly
to northwesterly flow will transition the lake- enhanced snow to=20
lake effect snow over northern WI into the U.P. tonight into
Wednesday where the 850-lake temperature difference will be >15C=20
(-10 to -13C at 850mb and a lake temperature around 5C). Lake=20
effect snow will break out for the L.P. of MI Wednesday afternoon
and off the eastern Great Lakes late Wednesday night. The threat
for single-band LES exists over northern MI Thursday/Thursday night
and the eastern Great Lakes Thursday. Expect 850mb temperatures of
<-10C over Lakes Erie/Ontario SSTs around +10C, allowing intense=20
lake bands to persist on WSW to W to WNW flow as the cyclone shifts
north of the region. Single banded snow will drop southward and=20
become more multi-banded downwind of Lake Erie but may retain a=20
stronger single band off Lake Ontario. Multi- banded snow will=20
persist across the Upper Great Lakes as well through early Friday.=20

For the rest of the synoptic event, Day 1 WPC probabilities for >8"
are 50-90% from the northern MN/WI border through northern WI and
the western/central U.P. with potential for two feet centered on=20
the Porcupine Mtns. Day 1 snow probs for >4" greater than 40%=20
extend northeast from the Twin Cities across north-central WI.=20
Considerable LES is expected after the surface low passes late=20
tonight through Wednesday with Day 2 snow probs for >12" 50 to 80%=20
for most of the U.P. the northern L.P. west from I-75 (as well as=20
30% south of Grand Rapids). For Day 2.5 the snow probs for >8" are=20
50-90% southeast of Lake Erie (including the Chautauqua Ridge into
northwest PA) and over the Tug Hill.=20


...Cascades through Northern Rockies...=20
Days 1-2...

A strong WNWly upper jet shifts across Washington State tonight
with sufficient Pacific Moisture for the Cascades (snow levels=20
around 4000ft rising to 5000ft) continuing for the Northern Rockies
into Wednesday where snow levels rise from 3000ft to 4000ft. Day 1
snow probs for >6" are 40-60% above these snow levels for the WA
Cascades, Bitterroots to the Absarokas.=20

High moisture plume ahead of the next wave tracks into Oregon
Wednesday with snow levels rising over 8000ft in OR Wednesday
afternoon with WA snow levels of 6000ft. Day 2 snow probs for >6"
are limited to the high WA Cascades.


...Glacier NP through Dakotas to Iowa...=20
Day 3...

...Increasing Winter Storm Threat Friday into/through the
Weekend...

The next winter storm to affect the central U.S. comes from a=20
Pacific shortwave low that crosses Washington State Thursday night=20
that combines with a shortwave trough that drops from the Canadian
Arctic Wednesday night, reaching Montana (and thus the connection
to the NW low) Thursday night. This combined longwave trough digs
across the northern Rockies Friday as lee-side surface cyclogenesis
occurs over eastern WY/CO. Confidence is increasing that a=20
resultant developing low pressure system then tracks east over the=20
central Plains Friday night with ample Gulf moisture allowing heavy
snow bands to set up across portions of the Midwest.

Of particular note for Thursday night/Friday is the Pacific
moisture combining with Gulf-sourced moisture with strong dynamics
ahead of the Pacific low (which opens Thursday night as the
northern stream trough approaches) allowing heavy snow bands to
develop over much of the MT Rockies and adjacent High Plains. Day=20
3 snow probabilities for >6" there are around 20% in a swath that
tracks just north over Great Falls with 40-80% values for any and
all terrain north of the Red Lodge portion of the Absarokas.=20

As the low develops Friday, a deformation axis of snow develops
across South Dakota and stretches into Iowa by 00Z Saturday. Day 3
snow probs for >4" are currently limited to 10-40% mainly in
eastern SD, but it's that banding that further develops and pivots
over the Midwest for much of Saturday.



The probability of significant ice across the CONUS is less than=20
10 percent.

Jackson


...Winter Storm Key Messages are in effect for the ongoing system=20
over the Upper Midwest and Great Lakes (link one below) and new=20
Key Messages are in production for the next wave (link two below) that
reaches the Northern Plains Thursday night and crosses the Great=20
Lakes through Sunday...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!4D5seMbfgWTVEv3GFrgjqqfSu-WjjwVo0HYX4BGYOLHZM= ASgNnyhPvfDYvN7k7rjdLjy6M2Tn9Fe3jRAzRog-FLWKQk$=20

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!4D5seMbfgWTVEv3GFrgjqqfSu-WjjwVo0HYX4BGYOLHZM= ASgNnyhPvfDYvN7k7rjdLjy6M2Tn9Fe3jRAzRogjtma3wE$=20



$$

=3D =3D =3D
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FOUS11 KWBC 260756
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
256 AM EST Wed Nov 26 2025

Valid 12Z Wed Nov 26 2025 - 12Z Sat Nov 29 2025


...Significant winter storm with localized blizzard conditions=20
will continue to impact parts of the Upper Midwest/Great Lakes=20
through Wednesday as lake effect snow intensifies into Thanksgiving
and Friday for the eastern Great Lakes...

...Confidence increasing on a second winter storm to affect the=20
Northern Plains Friday and the Midwest/Great Lakes Friday night=20
into Sunday...


...Key Messages for both systems are in effect and linked below...


...Upper Midwest/Great Lakes...=20
Days 1-3...

Deepening area of low pressure over the U.P. of Michigan will=20
reach peak intensity today as it moves eastward into Canada.=20
Northerly flow on its northwest side will continue to wrap in=20
moisture all the way around from the Northeast US with additional=20
infusion from Lake Superior. Lake enhanced snow will transition to=20
lake effect snow over northern WI and the U.P. of Michigan this=20 afternoon/evening and continue through Thursday and into Friday as=20
upper troughing will be slow to move out. NW flow across Lake=20
Michigan will signal the start of lake effect snow into the Lower=20
Peninsula as well, starting overnight. Lastly, after the cold front
clears through western NYS today, the lake machine will pick up=20
off of Lakes Erie and Ontario and continue through Friday and into=20
Saturday morning as additional height falls and PVA flow out of=20
Ontario across the Great Lakes. Winds will remain blustery to=20
strong at times (especially along lake shores), creating blowing=20
and drifting snow. The snow bands off of the eastern lakes will=20
start as single bands on SW to WSW flow before transitioning to=20
more multi-bands off at least Lake Erie as the flow veers to W then
WNW and NW on Friday.=20

Snow will accumulate rapidly under the more intense lake bands=20
that remain over the same area. The most favored locations for this
will be over the western to central U.P. of Michigan where the=20
multi- banded flow can still be quite intense. WPC probabilities=20
for an additional 8 inches of snow after 12Z today are at least 50%
over northern WI, most of the U.P. of Michigan (except for areas=20
closer to Lake Michigan), northwest Lower Michigan, northeastern=20
Ohio, northwestern PA, southwestern NY, and around the Tug Hill=20
Plateau. Within these regions, there is a smaller but still=20
significant area of probabilities >50% for 18 inches of snow.=20
Isolated totals could exceed 30 inches, including what has already=20 fallen.=20

Travel will be difficult and perhaps impossible at times due to=20
snow- covered roads, blowing snow, and low visibility.=20


...Northern Rockies...=20
Day 1...

Pacific system moving through WA/OR this morning will weaken but=20
retain its moisture through the northern Rockies. Generally lighter
snow is expected with moderate (30-60%) probabilities of at least=20
6 inches of snow for parts of the Absarokas and south central MT=20
ranges.=20


...Cascades, Northern Rockies/Plains to the Corn Belt...
Days 2-3...

The next Pacific system will approach the coast late tonight with=20
some light WAA-driven snow to the WA Cascades. Bulk of the=20
precipitation comes in on Thursday with high snow levels around=20
5000ft (north) to 7000ft (south), limiting accumulations to the=20
higher mountains. However, the mid-level shortwave will maintain=20
its identity as it crosses the Divide and is joined by an incoming=20
shortwave out of western Canada Friday. This combined longwave=20
trough will then digs through the Rockies as lee-side surface=20
cyclogenesis occurs over eastern WY/CO Friday afternoon. High=20
pressure following from Canada will help support some lower-level=20 upslope-enhanced snow over western MT where snow could be heavy at=20
times over the Lewis Range around Glacier NP. WPC probabilities for
at least 8 inches of snow are >50% over the northwestern MT=20
ranges. Over the valley floors, WPC probabilities for at least 4=20
inches of snow are generally >50% east of the Divide and including=20
the Absarokas and Bighorns.

Farther east, north of the developing surface low, sfc-850=20
troughing and WAA will enhance snow as well over=20
northern/northeastern MT that will eventually stretch=20
eastward/southeastward onto the Northern Plains Friday afternoon.=20
The addition of Gulf moisture from the south will help the snow=20
quickly expand ESE from the Plains to the Corn Belt by Friday=20
evening and continue into early Saturday, driven by 850-700 WAA and
surface convergence near/north of the warm front. By early=20
Saturday, the upper jet will sharpen along 100W and help to=20
continue to deepen the surface low over the central Plains. Light=20
to moderate snow will continue across the Corn Belt and become=20
heavier by the end of this forecast period (to continue into the=20
medium range). Through 12Z Saturday, WPC probabilities for at least
4 inches of snow are >30% from along the ND/SD border=20
southeastward through southwestern MN into Iowa. There (northern=20
Iowa), low chances (10-30%) of at least 6 inches of snow are shown=20
with more to come.


The probability of significant ice across the CONUS is less than=20
10 percent.

Fracasso


...Winter Storm Key Messages are in effect. Please see current Key
Messages below...

Ongoing storm:

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!67bOiLvMYtS1-WWIqNX8W1wwqqjbRDhtwJhwysHg9qQnP= olnpwJlNXfvYYUApTN3uV-YUEATpPITnOvf32225fCX0SA$=20

Next system:

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!67bOiLvMYtS1-WWIqNX8W1wwqqjbRDhtwJhwysHg9qQnP= olnpwJlNXfvYYUApTN3uV-YUEATpPITnOvf3222AR5asso$=20



$$

=3D =3D =3D
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FOUS11 KWBC 262025
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
325 PM EST Wed Nov 26 2025

Valid 12Z Wed Nov 26 2025 - 12Z Sat Nov 29 2025


...Significant winter storm with localized blizzard conditions will=20=20 continue to impact parts of the Upper Midwest/Great Lakes through=20
Wednesday as lake effect snow intensifies into Thanksgiving and=20
Friday for the eastern Great Lakes...

...Confidence increasing on a second winter storm to affect the
Northern Plains Friday and the Midwest/Great Lakes Friday night=20
into Sunday...


...Key Messages for both systems are in effect and linked below...


...Great Lakes...=20
Days 1-2...

Strong surface cyclone, 991mb over the central U.P. of Michigan
this afternoon has a well- defined axis of deformation situated=20
over western portions of Lake Superior down through Wisconsin.=20
Peak cyclone intensity is now with a gradual occlusion phase
expected as it shifts east tonight. Powerful north to northwest=20
flow will continue to spread in behind the system making for
prolific lake effect snow (LES). This remains downwind of Lake=20
Superior through the overnight period with heavy snowfall=20
situated across all of the Michigan U.P. and the heaviest focused=20
across the the area from Ironwood over to Marquette. Lake effect=20
snows will increase over western lower Michigan through this
evening as WSWly flow veers to WNWly and increasing cold air
advection. General persistence in the flow coupled with multiple=20
shortwave perturbations moving around the periphery of the ULL=20
positioned over the U.P. and adjacent Ontario will maintain to a=20
multi- band structure downwind of Lake Michigan. Strongest bands=20
will likely reside off northern Lake Michigan down through Traverse
City with hi-res CAMs and Canadian Regional highlighting heavy
narrow banding (nearly single banding) from Lake Superior and
northern Lake Michigan fetch to the area northwest of Gaylord
through Thursday night. LES threat diminishes Friday as the flow
decreases with the low approaches the Gulf of St. Lawrence.=20

Downstream of the eastern Lakes of Erie and Ontario, persistent=20
LES pattern will ensue this evening behind the swift moving cold=20
front with snow formation across both lakes by midnight.=20
Prevailing southwest flow off Lake Erie will kick off the banding=20
along the southern periphery of the Lake up through the eastern=20
regions before manifesting into a more consolidated band structure=20
as it drifts south overnight. Winds will veer more out of the west=20
and northwest by Thursday afternoon with the banding positioning=20
becoming more pronounced off the southern periphery of Erie leading
to several inches of snow falling in the adjacent terrain downwind
of the Lake. Lake Ontario will see a similar pattern with=20
southwesterly flow veering back west in a similar time scale. This=20
will lead to areas of the Tug Hill and places downwind of the Lake=20
off I-81 seeing the initial heavy LES signature, eventually with=20
the banding shifting towards the southeast side of Lake Ontario.=20
Initial indications are for a long- fetch connection between Huron=20
and Ontario could enhance banding downwind of the lake on Friday=20
leading to several inches of snowfall across the southern portions=20
of the Tug Hill and points south and west.=20

WPC probabilities for an additional 8 inches of snow after 00Z=20
Thursday are at least 50% over much of the U.P. of Michigan (except=20
for areas closer to Lake Michigan), northwest Lower Michigan, far-=20 northeastern Ohio, northwestern PA, southwestern NY, and around the=20
Tug Hill Plateau. Within these regions, there is a smaller but still=20 significant area of probabilities between 40-70% for 18 inches of=20
snow. Isolated totals could exceed 30 inches, including what has=20
already fallen across the Michigan U.P. Best chances are likely over=20
the western U.P. terrain, areas downwind of Lake Michigan and=20
Traverse Bay, I-90 corridor along the southern lake shores of Erie,=20
and the Tug Hill down through Oswego county in western New York=20
state.

Travel will be difficult and perhaps impossible at times due to snow-
covered roads, blowing snow, and low visibility.

Kleebauer/Jackson


...Northwest to Montana...=20
Days 1-2...

Developed low arrives to the WA Coast early Thursday with elevated
snow levels dropping to around 5000ft in the Cascades through the=20
day Thursday. Day 1.5 snow probs for >8" are 30-60% for the higher
WA Cascades.=20

An approaching shortwave trough descends Alberta Thursday night=20
and meets this low over ID/western MT on Friday. This combined=20
trough expands over the northern Rockies on Friday, promoting=20
downstream lee-side cyclogenesis near the eastern WY/CO border=20
Friday morning. 1040mb+ surface high pressure following from Canada
will help support some lower- level upslope-enhanced snow over=20
western MT where snow could be heavy at times over the Lewis Range=20
around Glacier NP particularly Thursday night. Day 2 WPC=20
probabilities for >8" snow are 50 to 80% over the northwestern MT=20
ranges down to the Bitterroots.

The arrival of Arctic air Thursday night allows snow for the
valleys/Plains of northern MT through Friday. Banding intensifies=20
north of the developing surface low with sfc-850 troughing and WAA
enhancing rates across northern MT through Friday morning with
lighter snows for the rest of the state into Friday evening. Day 2
snow probs for >6" are 20-50% over north-central MT.=20


...Northern Plains through the Midwest...
Days 2/3...

A low level frontogenetical band will set up along the baroclinic
zone northeast of the developing low Friday. Expect moderate to
locally heavy snow to establish in an ever expanding swath of snow
across southwest ND and much of SD Friday, reaching central Iowa by
Friday evening. 3-6" snowfall can be generally expected through
this band with locally higher amounts possible given slow motion
away from its orientation allowing some prolonged snowfall.

By early Saturday, the upper trough will push onto the High Plains,
the surface low is well developed over southern KS with an inverted
trough extending northeast to Wisconsin. Broad cyclonic flow around
this trough with Gulf- sourced moisture allows for rapid expansion
to the precip shield Friday night/Saturday with ample cold air for
snow both on the WAA ahead of the low/ and through the entire back
side/comma head. Broad coverage of moderate to heavy snow develops
Friday night over eastern SD/southern MN/northern IA with expansion
east to lower Michigan then through Saturday. A strong pressure
gradient will make for blustery conditions. Probabilities for
notable snow continue to increase with current Day 3 WPC snow probs
for >8" 40-75% over southern MN down through central Iowa with a
contour of 40% >6" snow from far eastern SD clipping northeast Neb
and including much of northern IL, southwestern WI, and up to the
Twin Cities in MN.



The probability of significant ice across the CONUS is less than=20
10 percent.

Jackson


...Winter Storm Key Messages are linked below...

Lake Effect Snow:

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!-l_s6iqeeDLG8U0cpRm4Ugv_XIj_L2CQQzY8a-JrBs0c_= c23jxXUqD4At1cseASflzM56Gg8cSClQJW3ckc29S1aTEE$=20

Northern Plains through Midwest System Friday-Sunday:

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!-l_s6iqeeDLG8U0cpRm4Ugv_XIj_L2CQQzY8a-JrBs0c_= c23jxXUqD4At1cseASflzM56Gg8cSClQJW3ckc2aqw0z4A$=20



$$

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FOUS11 KWBC 270840
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
340 AM EST Thu Nov 27 2025

Valid 12Z Thu Nov 27 2025 - 12Z Sun Nov 30 2025

...Great Lakes...=20
Days 1-2...

Long duration and impressive lake effect snow (LES) event ramps up
today and continues through Friday with prolific snowfall totals
likely in the favored snow belts SE of the Lakes.

This event is driven by a large closed 500mb low which will be over
southeast Ontario to begin the period. This low will spin nearly in
place through this evening before secondary vorticity energy
rotating into its base helps pivot it off to the east on Friday. A
final piece of energy, a strung-out vorticity lobe, will then move
across the Great Lakes Friday aftn, pulling the entire system to
the east and resulting in warm-to-neutral temperature advection by
Friday night, bringing an end to this event.

With strong cyclonic flow covering the region, NW winds will bring
strong cold advection (CAA) across the lakes to produce this
impressive LES. 850mb temps are progged to fall to -10C to -15C,=20
which when moving across lake temperatures that are still generally
+6C to +10C according to GLERL, will produce increasingly steep=20
lapse rates, SBCAPE as high as 800-1000 J/kg, and inversion depths
potentially reaching 700mb from the surface. This all will support
intense snowfall rates for which both the HREF and WPC snowband
tool suggest will reach 1-2"/hr within narrow bands, and locally
heavier snowfall rates cannot be ruled out.

While the bands may twist and pivot at times due to wind
fluctuations, in general they should be pretty persistent and
focused across the northern U.P and far NW L.P. of MI through
Friday morning, with more focused and longer-duration bands
impacting the Chautauqua Ridge and Tug Hill Plateau into Friday
night. This will result in storm total snowfall that has a high
probability (>70%) of exceeding 12 inches near Traverse City, MI,
as well as east of Lakes Ontario and Erie. Locally, more than than
2 feet of snow is possible (10-30% chance according to WPC=20
probabilities) across the Chautauqua Ridge and Tug Hill Plateau.

Key Messages remain in effect for this system, and are linked below
(Key Message #1).


...Northern High Plains through the Great Lakes...
Days 1-3...

...Significant winter storm likely to impact portions of the
Northern Plains, Upper Midwest, and Great Lakes through this
weekend...

A closed low off the WA coast will dive rapidly southeast while
opening, reaching the Northern Rockies by Friday morning. This wave
interacting with a stationary front draped across the region and a strengthening upstream jet streak will help spread precipitation
into the High Plains of MT very late D1 into D2 (around 12Z
Friday). Temperatures will be plenty cold for all snow as
precipitation continues to expand into the Dakotas, and the
evolution of this shortwave will drive the stationary front
southward as a cold front, leading to even colder temperatures and
dry fluffy snow into D2. Ascent during this period will be
generally modest, but as snowfall expands, WPC probabilities
suggest a moderate risk (50-70% chance) for at least 4 inches of
snow from northeast Montana through eastern South Dakota. This
jet-streak forced band has intensified in recent model progs, so
locally heavier snow is possible, especially across South Dakota
where a stripe of 700-600mb fgen gets intensified through the jet
structure.

Thereafter, the system amplifies to become much more impressive=20
with expanding heavy precipitation into the Upper Midwest Friday=20
night through Saturday. The mid-level trough diving into the=20
Central Plains will sharpen, and as the vort swings into the base=20
of the longer wave trough it will force a negative tilt coincident=20
with the development of coupled jet streaks (one strengthening over
the Central Plains and another exiting the Great Lakes) to produce
robust ascent. This overlapping synoptic lift will help strengthen
a surface low developing in the lee of the CO Rockies and then=20
tracking east, and eventually northeast, from KS through IL and=20
into MI by 12Z Sunday.

Downstream of this surface low, warm and moist advection will
rapidly intensify as 850mb winds surging to above 50kts draw
elevated PWs northward from the Gulf, reflected by PW anomalies
surging above the 90th percentile according to NAEFS into KS/MO/IA.
This will be accompanied by a theta-e ridge lifting northward as
well, and although a true TROWAL is not currently progged, this
theta-e ridge will still promote additional moisture and some
elevated warm air to promote modest potential instability. This
evolution suggests intense WAA, which is reflected as well by model
output, which will help expand precipitation from the Dakotas and
Iowa Friday night, to encompass most of the Upper Midwest Saturday,
and then reach the Great Lakes Saturday night.=20

As far as snowfall amounts and impacts, there is still considerable
uncertainty due to model placement and timing of this system. In
general, the models are in good agreement with the large-scale
evolution, but with such strong WAA in place, even minor timing or
latitudinal differences can result in significant changes to
impacts. Evaluation of D3 and D4 clusters suggests the GEFS is
potentially a bit under-dispersed with its faster trough
progression, while the ECENS/CMCE feature more spread to support a
variety of solutions suggesting a continued ensemble approach
especially by D3. However, some condensing of the spread D2 boosts
the confidence that light to moderate snow will expand into the
Corn Belt before 12Z Saturday, before pushing east thereafter.

In general, this event appears to be of longer-duration with=20
moderate snowfall rates driven by 280-290K isentropic ascent
combined with modest fgen beneath the weak theta-e ridge aloft.=20
However, as is the case with most strong WAA events, a narrow=20
corridor of heavier snowfall with rates greater than 1"/hr appears=20
likely, especially near MO/IA where conditional instability is in=20
place and strong fgen drives lift into the DGZ. The DGZ appears to=20
be elevated and shallow in most places (although some SREF=20
probabilities for 100mb of depth do eclipse 30%), but locally some=20
banding could produce more intense rates leading to more=20
substantial amounts and impacts.

Currently, WPC probabilities are extremely high (>90%) for more
than 4 inches in a large swath from eastern SD through most of IA,
northern IL, southern WI, and into parts of lower Michigan.
However, the axis of heaviest snowfall is likely from southern IA
through western Michigan, where WPC probabilities are high (>70%)
for more than 8 inches of accumulation, and locally 12+ inches of
snow is possible, and there are several members within the WSE
plumes which indicate more than 15 inches in some areas. The exact
placement of the heaviest snow is still in question due to a=20
continued southern trend in guidance, but the long duration of this
event, combined with locally heavier snow rates, leads to high=20
confidence in an impactful event. This is additionally reflected by
WSSI-P probabilities which exceed 90% (50%) for moderate (major)=20
impacts for portions of IA, IL, and WI. Post-Thanksgiving travel is
likely to be extremely disrupted during this event.

Key Messages are in effect for this system and are linked below
(Key Message #2).


...Cascades and Northern Rockies...=20
Days 1-2...

Closed mid-level low west of WA will push onshore Thursday evening
while opening into a shortwave as it lifts into the Northern
Rockies. Downstream of this impulse, modest warm and moist
advection will surge IVT to above 250 kg/m/s into the Cascades,
leading to increasing coverage and intensity of precipitation. Snow
levels will climb to around 6000 ft within this IVT plume, but then
crash quickly as the cold front accompanying this system pushes
east as well. At the same time, a secondary front will dig
southward from Alberta, Canada into the Northern Rockies, and
westerly flow aloft pushing higher moisture into this region will
interact with the terrain and this front to produce ascent and
expanding precipitation. At the same time, the overlap of the
strongest height falls downstream of the filling shortwave with an
amplifying jet streak will likely cause surface low development
Friday morning, helping to additionally enhance ascent before
everything kicks off to the east by Friday night.

This evolution will likely cause moderate to at times heavy snow
(heaviest in the Northern Rockies due to fgen and upslope
enhancement), with snow levels fluctuating around 3000-4000 ft, but
remaining near the surface east of the Continental Divide and into
the High Plains. WPC probabilities are moderate (>50%) for 4+
inches D1 across the Cascades, but high (>70%) for 6+ inches near
Glacier NP and the surrounding Northern Rockies. During D2 snowfall
shuts off across the Cascades, but continues in the Northern
Rockies with an additional moderate chance (50-70%) for 6+ inches
of snow again. Travel across most of the Northern Rockies passes
will likely be impacted during this snow.


The probability of significant ice across the CONUS is less than=20
10 percent.

Weiss


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!71PkPC9AEcSguo65jYfOcG0iB12Z-tOnE0FjdAaVTtrFj= 3ARvInbHUaxEL7Y-FFu1kMuU5m89_2mgxWYr5rimWePIrw$=20

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!71PkPC9AEcSguo65jYfOcG0iB12Z-tOnE0FjdAaVTtrFj= 3ARvInbHUaxEL7Y-FFu1kMuU5m89_2mgxWYr5riXp5Fw8Y$=20


$$

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FOUS11 KWBC 272050
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
350 PM EST Thu Nov 27 2025

Valid 00Z Fri Nov 28 2025 - 00Z Mon Dec 01 2025

...Great Lakes...=20
Day 1...

Long duration lake effect snow (LES) event continues through=20
Friday with prolific snowfall totals in the favored snow belts for
NWly flow in northern MI and for WNWly flow off Lakes Erie and
Ontario.=20

Deep low remains over central Quebec through Friday before lifting
to Labrador. The mid level trough axis associated with the low is
currently over the eastern U.P. and will swing east over the
eastern Lakes tonight. Saturated DGZ zones will maintain efficient
snow production over the autumnally warm lakes. Ridging finally=20
spreads east over the region Friday night ending the LES.=20

For Michigan expect individual banding in NW flow over the eastern
U.P. with additional banding from added fetch from Lake Michigan=20
into the Tip of the Mitt will persist through Friday morning. Day=20
1 WPC snow probs for >8" additional are 40-70% in the same narrow=20
zones being impacted now.=20

Eastern Great Lakes see ideal multiple lake fetch in cyclonic flow as
seen in current radar mosaics with banding from Superior,=20
Michigan, Huron, and Ontario into the Tug Hill and fetch from
Superior, lower Michigan, and Erie into the Chautauqua Ridge of
western NY and east of Cleveland. WPC Day 1 snow probs for >8"
additional are 50-70% for these features, and over 80% on the
Chautauqua Ridge where probs for >12" are 50-70%.

Key Messages remain in effect for this system (link #1 below).


...Northern High Plains through the Midwest into the Northeast...=20
Days 1-3...

...Significant winter storm to impact large portions of the=20
Northern Plains, Midwest, and Great Lakes through this weekend...

A closed low along the WA coast this afternoon will shift southeast
tonight while opening, crossing the Northern Rockies Friday. This=20
wave is shunted on the southern trajectory from a northern stream
trough currently shifting south down the Canadian Rockies tonight.
This trough interaction and a strengthening upstream jet streak=20
will help spread moderate snow bands from Glacier NP through
northern MT tonight. Temperatures will be plenty cold for all snow
in the bands with some freezing rain potential on the southern
portions of precip over south-central MT overnight.=20

The frontogenetical banding quickly extends across the Dakotas
Friday morning, reaching western Iowa in the afternoon. This
banding is north of a developing lee-side low ahead of the merging
troughs that develops over eastern CO Friday and shifts east over
the KS/OK border as it further develops Friday night. This allows
the fgen band to transition into a deformation band around an
inverted trough extending from the surface low. Day 1.5 snow probs
for >6" are 30-60% from Northeast MT through central Iowa.=20

Thereafter, the system amplifies to become much more impressive=20
with expanding heavy precipitation through the central Midwest=20
Friday night through Saturday. The mid-level trough diving into the
Central Plains will sharpen, and as the vort swings into the base=20
of the longer wave trough it will force a negative tilt coincident=20
with the development of coupled jet streaks (one strengthening over
the Central Plains and another exiting the Great Lakes) to produce
strong ascent. This overlapping synoptic lift will help strengthen
a surface low developing in the lee of the CO Rockies and then=20
tracking east, and eventually northeast, from KS through IL and=20
into southern MI by 12Z Sunday.

Downstream of this surface low, warm and moist advection will
rapidly intensify as 850mb winds surging to above 50kts draw
elevated PWs northward from the Gulf, reflected by PW anomalies
surging above the 90th percentile according to NAEFS into KS/MO/IA.
This will be accompanied by a theta-e ridge lifting northward as
well, and although a true TROWAL is not currently progged, this
theta-e ridge will still promote additional moisture and some
elevated warm air to promote modest potential instability. This
intense WAA will help expand precipitation from the Dakotas and=20
Iowa Friday night, to encompass most of the Upper Midwest Saturday,
and then cross Lower Michigan Saturday night before surging up the
Interior Northeast Sunday.

Confidence continues to increase in the track of the low with a
preference for the northern end of the precip shield given to the
EC/GFS which are farther north (through central WI with 0.5" QPF) than
the CMC/UKMET. The broad precip shield and ample cold air will
result in pivoting heavy bands with the highest totals as of now
forecast over central IA where a foot is possible. As noted before
the DGZ depth will be a concern at times and with so much precip
from WAA, the ratios should be somewhat limited over IL/IN ahead of
the system.=20

Day 2/2.5 WPC snow probs for >8" are over 30% from far southeast
SD/northeast Neb across all but far southwest IA, southern MN,
central and southern WI, and northern IL. Day 3 probs for >8" are
20-40% for much of the L.P. of Michigan. Post-Thanksgiving travel=20
is likely to be extremely disrupted during this event.

Key Messages remain in effect for this system (Link #2 below).


...Cascades and Northern Rockies...=20
Days 1-2...

Low crossing WA tonight with snow levels in the Cascades around
5000ft. Pacific moisture surges inland ahead with snow levels over
the northern Rockies of 4000-5000ft which decrease after snow
tapers behind a northern stream trough descending from the Canadian
Rockies. Day 1 snow probs for >6" are 40% in the high WA Cascades=20
and 50-80% across all western MT ranges into northern ID.=20

A combined upper trough shifts down the Rockies Friday with Day 1.5
snow probs for >6" 40-70% in the Tetons, Absarokas, Bighorns, and
ranges of north-central C0.=20


Jackson



...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!8umiVbKQN4ZSupkAbsvNAy8egWLsRvjnEIX-waL1s0UKs= _UdFepA7tN5qL700FGj-H401SxDmvGxZyaBuiBN2o7Ywhc$=20

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!8umiVbKQN4ZSupkAbsvNAy8egWLsRvjnEIX-waL1s0UKs= _UdFepA7tN5qL700FGj-H401SxDmvGxZyaBuiBN6Di-u1E$=20




$$

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FOUS11 KWBC 280707
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
207 AM EST Fri Nov 28 2025

Valid 12Z Fri Nov 28 2025 - 12Z Mon Dec 01 2025

...Great Lakes & Northeast...=20
Day 1...

Cyclonic flow aloft will persist a long duration lake effect snow
(LES) event into Saturday morning, with prolific snowfall totals
likely in a few areas.=20

The period begins with an elongated but closed mid-level low
centered over Quebec driving lowered heights into the Northeast.
Rounding the base of this trough, a secondary shortwave and
elongated vorticity lobe will swing eastward through the Great=20
Lakes and into the Northeast tonight, bringing a brief period of=20
shortwave ridging to the area tonight. This will be the evolution=20
to finally shut off the LES.

However, until then, two significantly impactful winter weather
areas are expected. The first is in the favored WNW snow belts off
the Great Lakes: from the eastern U.P. through the NW L.P. of MI,
and then downstream along the Chautauqua Ridge and the Tug Hill
Plateau. 850mb temps falling to as low as -15C (-10C far east
portions) will drive steepening lapse rates across lake
temperatures that are still generally +6C to +10C according to
GLERL. The cooling column will keep the DGZ relatively shallow, but
favorable ascent crossing the DGZ efficiently will produce bands of
very heavy snow for which the HREF indicates has a >60% chance of
exceeding 1"/hr, and will likely reach 2-3"/hr at times in response
to deep inversion depths as high as 700mb. Although winds will
fluctuate just enough to prevent stationary single bands (plus the
fetch direction is not along the long-breadth of the lakes in many
areas), narrow corridors of heavy snow are expected, especially
where any upstream connection can occur from Huron/Superior/Georgian
Bay to Lakes Erie and Ontario. The heaviest snow is likely D1 just
southeast of Lakes Erie and Ontario where WPC probabilities for 8+
inches reach 50-90%, and storm total snowfall from this event=20
could be over 2 feet in a few locations.

In addition to the LES, a strong cold front pressing east from the
Lakes early this morning will reach the Atlantic coast this=20
evening. The guidance has become increasingly excited in the
potential for convective snow showers or snow squalls along this
front, as reflected by a snow-squall parameter well above 1. The
environment appears favorable for snow squalls from western PA
through northern ME as the front passes east, moving across an
environment with SBCAPE as high as 250 J/kg coincident with modest
0-2km fgen and theta-e lapse rates falling below 0C/km. Moisture
may be the limiting factor away from the Great Lakes, so the best
chance for squalls appears to be well inland of these states, but
any place that does receive a squall this afternoon would likely
experience dangerous travel due to rapidly changing conditions with
briefly heavy snow and gusty winds.

Key Messages remain in effect for this system (link #1 below).


...Northern High Plains through the Midwest into the Northeast...=20
Days 1-3...

...Significant winter storm to impact large portions of the=20
Northern Plains, Midwest, and Great Lakes through this weekend...

The first widespread significant winter storm of the season begins
in earnest today as a positively tilted shortwave trough emerges
from the Pacific Northwest and tracks southeast into the
Northern/Central Plains. As a secondary vorticity impulses rotates
into the trough, this will force downstream amplification of the
mid-level pattern, resulting in a negatively tilted trough and
increasing ascent downstream into the Upper Midwest and Great
Lakes. At the same time, jet streaks both upstream and downstream
of this amplifying trough will begin to couple, producing even more
intense deep layer lift, and a surface low will result - first in
the lee of the Rockies and then tracking gradually northeast into
MI by Sunday morning. This low will then continue to deepen as it
shifts across southeast Canada and exits into the Canadian
Maritimes by the end of the forecast period /12Z Monday/.

The guidance has come into much better agreement with the track and
intensity of this system, and while small temporal and spatial
differences among the ensembles still exist, the spread is minimal
compared to previous model runs leading to higher confidence in the
evolution. As the low deepens and moves northeast, impressive WAA
will develop downstream of the developing cyclone, spreading PWs
which will exceed the 90th percentile northward into MO/IA. The
accompanying theta-e ridge will surge in tandem and isentropically
ascent the region, and while guidance is still not suggesting a
strong TROWAL, at least subtle warm air aloft will help develop
modest conditional instability. The coincident and impressive 290K
isentropic ascent will lead to expanding and intensifying
precipitation, with moderate snow likely across much of the
Northern Plains, Upper Midwest, and Great Lakes, especially Friday
night through Sunday morning.

On D1, the heaviest snowfall accumulations are likely in a narrow
band driven by the jet streak aloft and the accompanying
ageostrophic/fgen enhancement between 700-600mb. This will cause a
stripe of periodically heavy snow from southern ND through western
IA, and although the band should be narrow, snowfall rates of
0.5"-1"/hr are likely which could cause 4-6" of snow as reflected
by WPC probabilities for 4+ inches that reach above 70%.

However, the most significant part of this event begins late D1
across IA and then spreads east through D2 into MI. Here, the
impressive isentropic ascent will be quite moist as reflected by
mixing ratios of 4 g/kg on the 290K surface, leading to a rapidly
saturating column. While in general this upglide will result in
moderate snowfall rates, there appears to be an increasing risk for
heavier snowfall across portions of MO/IA/IL as the WAA forces
an increasing isothermal layer beneath the DGZ which also begins to
deepen. Cross-sections are more robust featuring a corridor of
folding theta-es surfaces within the elevated RH, suggesting a
greater potential for CSI and convective snowfall rates. There is
still some uncertainty into this since this signal is much more
robust tonight than previous model runs, but locally 1-2"/hr rates
appear possible which is supported by the WPC prototype snowband
tool despite a modest overall appearance of the evolution with
respect to conceptual models for heavy snow bands. Still, multiple
bands lifting northward for a long duration will result in
significant snowfall accumulations and major impacts for the post-
Thanksgiving holiday travel.=20

This will be a significant system with several waves of moderate to
heavy snowfall. On D2, the heaviest accumulations are expected from
far eastern NE through IA, northern IL, and southern WI. WPC
probabilities in this region are 70-90% for more than 6 inches of
snow, and locally as high as 50% for more than 12 inches, highest
near the Quad Cities of IA. Later D2 into D3 the heaviest snow
shifts eastward and eventually wanes in intensity, but additional
heavy snowfall exceeding 6" is possible, especially around Lake
Michigan and into the L.P. of MI. Event total snowfall may reach
15" in isolated locations Saturday.

Moderate snowfall is also expected across the interior northeast=20
where WPC probabilities D3 are as high as 50-70% for 4+ inches in=20
the higher terrain of VT, NH, and ME.

Key Messages remain in effect for this system (Link #2 below).


...Central Rockies...
Day 3...

A potent shortwave will drop out of the Pacific Northwest Sunday
morning and then move progressively southeast, reaching the Four
Corners Sunday night while maintaining a positive tilt. Late D3
this feature will begin to sharpen, with the resulting downstream
jet streak intensifying into the Central Plains. The overlap of the
RRQ of this jet streak with the greatest height falls ahead of the
trough axis will help spawn low pressure in the Great Basin, and
this low will help to increase ascent across the Central Rockies
Sunday evening. As the overall ascent increases, precipitation will
expand, and periods of moderate to heavy snow are likely, generally
above 5000 ft. This system is expected to remain progressive so
prolonged snowfall is not expected, but WPC probabilities indicate
a moderate risk (50-70% chance) of at least 6 inches of snowfall
across the CO Rockies and northern San Juans, with lighter
accumulations expected as far west as the Wasatch of Utah.


Weiss




...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!6Sc2F0cnium5fdExFU2gmXHPKlYB1f8bP0Ql_VmqDRwDR= tO2_L40P2nqWm2GPccQ_EI7PVD0CcUgKaNs5dlLL32TFvQ$=20

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!6Sc2F0cnium5fdExFU2gmXHPKlYB1f8bP0Ql_VmqDRwDR= tO2_L40P2nqWm2GPccQ_EI7PVD0CcUgKaNs5dlLAcOrDGE$=20



$$

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FOUS11 KWBC 281854
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
154 PM EST Fri Nov 28 2025

Valid 00Z Sat Nov 29 2025 - 00Z Tue Dec 02 2025

...Great Lakes & Northeast...=20
Day 1...

Persistent cyclonic flow will maintain the current long duration=20
lake effect snow (LES) event into Saturday morning leading to prolific
snowfall totals likely in a few areas.=20

Elongated but closed mid-level low remains centered over Quebec=20
driving lowered heights into the Northeastern CONUS. Rounding the=20
base of this trough, a secondary shortwave and elongated vorticity=20
lobe is swinging eastward through the western Great Lakes,
eventually making headway into the Northeast tonight, bringing a=20
brief period of shortwave ridging to the area overnight. This will=20
be the evolution to finally shut off the LES machine that's been=20
present the past 48+ hours.

However, until that transpires, two significantly impactful winter
weather areas continue through this afternoon and early evening.=20
The first is in the favored WNW snow belts off the Great Lakes:=20
from the eastern U.P. through the NW L.P. of MI, and then
downstream along the Chautauqua Ridge and the Tug Hill Plateau. 18z mesoanalysis indicates a broad expanse of 850mb temps between -10
to -15C, driving steepening lapse rates across lake temperatures
that are still generally +6C to +10C according to GLERL. The
cooling column will keep the DGZ relatively shallow, but favorable
ascent crossing the DGZ efficiently has aided in producing a
plethora of multi-band structures with hourly rates upwards of
1"/hr. Hourly max rates will likely reach 2-3"/hr at times in
response to deep inversion depths as high as 700mb, especially in
the singular band structure from a long fetch axis oriented from
Lake Huron down through Georgian Bay then back over Lake Ontario.
The aforementioned persistent singular band is well-defined at this
hour off Lake Ontario through Oswego county extending into=20
southern Tug Hill and areas downstream. This area will exhibit the=20
heaviest snowfall accumulations through the period with areas=20
residing in the band likely to attain well over 12" at this=20
juncture leading to snowfall totals eclipsing 2ft for the entirety=20
of the event.

In addition to the LES, a strong cold front pressing east from the
Lakes has allowed for convective snow showers or snow squalls=20
along this front. Regional radar composite shows a multitude of
convectively based snow showers/squalls across southern NY state
down through western and central PA. The environment remains
favorable as the front advances east with MUCAPE as high as 200=20
J/kg coincident with modest 0-2km fgen and theta-e lapse rates=20
falling below 0C/km centered over west-central PA as of 18z. Snow
squall warnings have been issued in response over the past few
hrs, a testament to the environmental favor in place. Any area that
receives these snow squalls will encounter the opportunity for=20
dangerous travel due to rapidly changing conditions with briefly=20
heavy snow and gusty winds.

Key Messages remain, but will be the final issuance for the event=20
(link #1 below).


...Northern High Plains through the Midwest into the Northeast...=20
Days 1-3...

...Significant winter storm to impact large portions of the=20
Northern Plains, Midwest, and Great Lakes through this weekend...

The previous forecast discussion remains very relevant for the
incoming significant winter storm development already materializing
over the Plains and Midwest. Latest UA analysis this afternoon
indicates a positively tilted shortwave trough emerging from the=20
Pacific Northwest, forecast to track southeast into the=20
Northern/Central Plains as we continue through this afternoon. As=20
a secondary vorticity impulses rotates into the trough, this will=20
force downstream amplification of the mid-level pattern, resulting=20
in a negatively tilted trough and increasing ascent downstream into
the Midwest and Great Lakes. At the same time, jet streaks both=20
upstream and downstream of this amplifying trough will begin to=20
couple, producing even more intense deep layer lift, and a surface=20
low will result - first in the lee of the Rockies and then tracking
gradually northeast into MI by Sunday morning. This low will then=20
continue to deepen as it shifts across southeast Canada and exits=20
into the Canadian Maritimes by the end of the forecast period /12Z=20
Monday/.

The guidance this morning has maintained general continuity with=20
better agreement on the track and intensity of this system, and=20
while small temporal and spatial differences among the ensembles=20
still exist, the spread is minimal compared to previous model runs=20
leading to a high confidence scenario in both the expected
evolution and snowfall forecast. As the low deepens and moves=20
northeast, impressive WAA will develop downstream of the developing
cyclone, spreading PWs which will exceed the 90th percentile=20
northward into MO/IA. The accompanying theta-e ridge will surge in=20
tandem and isentropically ascent the region, and while guidance is=20
still not suggesting a strong TROWAL, at least subtle warm air=20
aloft will help develop modest conditional instability. The=20
coincident and impressive 290K isentropic ascent will lead to=20
expanding and intensifying precipitation, with moderate snow likely
across much of the Northern Plains, Upper Midwest, and Great=20
Lakes, especially Friday night through Sunday morning.

On D1, the heaviest snowfall accumulations are likely in a narrow
band driven by the jet streak aloft and the accompanying
ageostrophic/fgen enhancement between 700-600mb. This has allowed
for a stripe of periodically heavy snow over parts of the Dakotas,
spreading into western IA as of the past few hrs. Despite the band=20
being relatively narrow, snowfall rates of 0.5"-1"/hr are likely=20
which could cause 4-6" of snow as reflected by WPC probabilities=20
for 4+ inches that reach above 70%.

However, the most significant part of this event begins later this
evening across IA, spreading eastward through D2 IL/WI/MI. Here,=20
the impressive isentropic ascent will be quite moist as reflected=20
by mixing ratios of 4 g/kg on the 290K surface, leading to a=20
rapidly saturating column. While in general this upglide will=20
result in moderate snowfall rates, there appears to be an=20
increasing risk for heavier snowfall across portions of MO/IA/IL as
the WAA forces an increasing isothermal layer beneath the DGZ=20
which also begins to deepen. Cross-sections are more robust=20
featuring a corridor of folding theta-e surfaces within the=20
elevated RH, suggesting a greater potential for CSI and convective=20
snowfall rates. There is still some uncertainty into this since=20
this signal is much more robust tonight than previous model runs,=20
but locally 1-2"/hr rates appear possible which is supported by the
WPC prototype snowband tool despite a modest overall appearance of
the evolution with respect to conceptual models for heavy snow=20
bands. Still, multiple bands lifting northward for a long duration=20
will result in significant snowfall accumulations and major impacts
for the post- Thanksgiving holiday travel.=20

This will be a significant system with several waves of moderate to
heavy snowfall. On D2, the heaviest accumulations are expected from
far eastern NE through IA, northern IL, and southern WI. WPC
probabilities in this region are 70-100% for more than 6 inches of
snow, and locally as high as 50-70% for more than 12 inches,=20
highest near the Cedar Rapids over into the Quad Cities of IA.=20
Later D2 into D3 the heaviest snow shifts eastward and eventually=20
wanes in intensity, but additional heavy snowfall exceeding 6" is=20
possible, especially around Lake Michigan and into the L.P. of MI.=20
Event total snowfall may reach upwards of 15+" in isolated=20
locations Saturday, potentially setting November and even=20
encroaching some all-time snowfall records for the 24hr and 48hr=20
periods.

Moderate snowfall is also expected across the interior northeast=20
where WPC probabilities D3 are as high as 50-70% for 4+ inches in=20
the higher terrain of VT, NH, and ME.

Key Messages remain in effect for this system (Link #2 below).


...Central Rockies...
Day 3...

No changes necessary to the anticipated evolution of the next
winter disturbance to impact the Central Rockies. A potent=20
shortwave will drop out of the Pacific Northwest Sunday morning,
moving progressively southeast, reaching the Four Corners Sunday=20
night while maintaining a positive tilt. Late D3 this feature will=20
begin to sharpen, with the resulting downstream jet streak=20
intensifying into the Central Plains. The overlap of the RRQ of=20
this jet streak with the greatest height falls ahead of the trough=20
axis will help spawn low pressure in the Great Basin, and this low=20
will help to increase ascent across the Central Rockies Sunday=20
evening. As the overall ascent increases, precipitation will=20
expand, and periods of moderate to heavy snow are likely, generally
above 5000 ft. This system is expected to remain progressive so=20
prolonged snowfall is not expected, but WPC probabilities indicate=20
a moderate risk (50-80% chance) of at least 6 inches of snowfall=20
across the CO Rockies and northern San Juans, with lighter=20
accumulations expected as far west as the Wasatch of Utah.


Weiss/Kleebauer


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!9HzmYz-mIE6DfhJQQBQsOzECv_KFcaoJzdylhJVfCiVsb= -Dbu3RKVB1zEOHkADoLaYbeS0vS7lK--9jlNEGcykLqUmg$=20

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!9HzmYz-mIE6DfhJQQBQsOzECv_KFcaoJzdylhJVfCiVsb= -Dbu3RKVB1zEOHkADoLaYbeS0vS7lK--9jlNEGckf1n8zY$=20



$$

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FOUS11 KWBC 290825
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
325 AM EST Sat Nov 29 2025

Valid 12Z Sat Nov 29 2025 - 12Z Tue Dec 02 2025


...Northern High Plains through the Midwest into the Northeast...=20
Days 1-2...

...Significant winter storm ramps up across the Midwest today...

A positively tilted shortwave trough diving out of Montana will
sharpen today across the Central Plains, and eventually take on a
negative tilt by this evening in response to secondary vorticity
energy rotating through its base. This evolution will result in
intensifying deep layer ascent in response to more significant
height falls overlapping mid-level divergence, and this will
additionally be aided by increasingly coupled upper jet streaks.
The surface low developing within this impressive ascent will then
deepen as it lifts northeast from Kansas /12Z Saturday/ to Michigan
/12Z Sunday/. This system will become increasingly progressive
through D2, reaching the Canadian Maritimes by 12Z Monday.

This evolution will yield an impressive swath of snow from the
Northern Plains through much of the Midwest and then into the Great
Lakes. As the low develops, increasing warm/moist advection will
surge PWs out of the Gulf, and PW anomalies above the 90th
percentile are progged by NAEFS to reach as far north as MO/IA.
This will occur during a period of intensifying 290K isentropic
ascent, which when occurring beneath the larger scale synoptic lift
will cause snowfall to expand quickly, and become heavy, especially
where 700-600mb fgen intensifies (both due to the WAA and the
ageostrophic response of the upper jet position). At the same time, cross-sections continue to indicate a threat for CSI due to folding
theta-e surfaces, which additionally will support periods of heavy
snowfall rates as laterally translating bands shift northeast
through the region. Snowfall rates of 1-2"/hr are likely (>80%
chance according to the HREF), which, although won't be constant,
will help rapidly accumulate snowfall even with SLRs that will be
around to slightly below climo most of the event.

This intense snowfall will result in widespread significant
impacts, and the WSSI-P indicates a 60-80% chance of major impacts
for parts of IA, IL, and WI, including the Des Moines, Chicago, and
Milwaukee metro areas. This will snarl travel during the busy
post-Thanksgiving holiday weekend. Where snow is the most intense
and longest lasting, record or near-record November snowfall is
possible, especially across eastern IA, southern WI, and northern
IL. This is also where the ECMWF EFI is above 0.9 with an SoT of
1-5, further indicating the potentially record-breaking November
snowfall.

WPC probabilities D1 are high (>70%) for at least 6" of snow from=20
central IA though southern MI, with locally more than 12" possible
(10-30% chance) in eastern IA, southern WI, and northern IL.
Isolated higher totals are possible as well where any banding can
persist due to local convergent features such as indicated by many
of the high-res models near Lake Michigan.

The most significant snowfall should wane quickly from west to east
by 12Z Sunday, but post-system NW flow will create some modest lake
effect snow (LES) across the U.P. and L.P. of MI, as well as east
of Lakes Erie and Ontario Sunday night. Additionally, some modest warm-advection snowfall is likely across the higher terrain of the
interior Northeast before snowfall comes to an end by 12Z Monday.
Additionally snowfall of more than 4 inches is likely (50-90%
chance) according to WPC probabilities from the Chautauqua Ridge
northeast through the higher terrain of the Adirondacks, and into
VT/NH/ME.

Key Messages remain in effect for this system (Key Message 2=20
below).


...Central Rockies through the Mid-Mississippi Valley...=20
Days 2-3...

The next system follows quickly behind the powerful storm across
the Midwest as progressive flow dominates the CONUS.

This system begins as a positively tilted shortwave emerging from
the Pacific Northwest and then digging rapidly into the Four
Corners states by 12Z Monday. As this impulse dives southeast, the
associated vorticity lobe will swing rapidly east, forcing the
evolution into a neutral tilt over the Central/Southern Plains D3,
and potentially becoming negatively tilted late in the forecast
period across the Mid-Mississippi Valley. During this evolution, a
downstream upper jet streak will amplify and pivot poleward over
the Central Plains to enhance deep layer lift. This should cause an
area of heavy snowfall D2 across the Central Rockies, including=20
the Wasatch, Uintas, and CO Rockies where snow levels of around
4000-5000 ft are expected. Although the system is progressive, PW
anomalies above the 90th percentile will support periods of heavy
snow, aided by upslope into the terrain, and WPC probabilities for
more than 4 inches of snow have increased to 70-90% across the Ruby
Mountains in NV, as well as the expanse of the Wasatch, Uintas, CO
Rockies, and San Juans. Locally as much as 12" of snow is possible
in the highest terrain of Colorado.

The forecast becomes more challenging into D3 as this system=20
pushes east. Although the surface wave is likely to wane across the Southern/Central Plains, the downstream impressive jet streak and=20
height falls invof the upper trough will persist. Late Monday, some
of the guidance indicates that the downstream jet and a secondary=20 sub-tropical jet streak emerging across Mexico will phase, leading=20
to secondary low pressure development across the Mississippi=20
Valley. As this occurs, precipitation will expand from the Gulf=20
Coast through the Mid-Mississippi Valley in response to=20
intensifying moist isentropic ascent along the 290K-300K surfaces.=20
Mixing ratios within this plume are progged at 4-8 g/kg, around the
75th-90th percentile for the date, indicative of the impressive
moisture availability in this system.=20

While there are still important timing, location, and thermal=20
differences among the various global members and their associated=20
ensembles, the trends are for a wetter and colder system which=20
could produce significant snow and mixed precipitation before 12Z=20
Tuesday. The AIFS and ECMWF EFI are both well southeast of the=20
highest NBM probabilities during D3, but the D3/D4 clusters=20
indicate high variability due to timing differences of the trough.=20
Despite this uncertainty, current WPC probabilities for at least 2"
of snow are moderate (30-70% chance) from central Kansas through=20
the western Ohio River Valley, with the potent jet streak aloft=20
helping to produce potential banded snow in this region.=20

Additionally, with warm moist air flooding northward from the Gulf
and a retreating cold high pressure in place, a zone of mixed
precipitation, including freezing rain, is likely from the Ozarks
through the southern Appalachians. There continues to be much
uncertainty in the axis of heaviest ice accretions, but
probabilities for at least some modest ice have come up tonight,
leading to increasing confidence in areas of impactful freezing
rain. At this time, WPC probabilities for 0.1" on D3 are as high as
30% in the Ozarks, and 30-50% in the southern Appalachians.

This system will likely continue beyond this forecast period while strengthening, and may create heavy snow across the interior Mid-
Atlantic and Northeast on Tuesday. For this reason, key messages
have been initiated (Key Message 3 below).


Weiss


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!6AjAsWQpkfwy645ER6VQR0wLShDHv63j-1-CD6L3akHfB= DlClvSPq3DonTR_1NKPbrp6WnFzXPoiq9k9rUpb3aiBrZE$=20

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!6AjAsWQpkfwy645ER6VQR0wLShDHv63j-1-CD6L3akHfB= DlClvSPq3DonTR_1NKPbrp6WnFzXPoiq9k9rUpbkFb3CDg$=20



$$

=3D =3D =3D
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FOUS11 KWBC 290829
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
329 AM EST Sat Nov 29 2025

Valid 12Z Sat Nov 29 2025 - 12Z Tue Dec 02 2025


...Northern High Plains through the Midwest into the Northeast...=20
Days 1-2...

...Significant winter storm ramps up across the Midwest today...

A positively tilted shortwave trough diving out of Montana will
sharpen today across the Central Plains, and eventually take on a
negative tilt by this evening in response to secondary vorticity
energy rotating through its base. This evolution will result in
intensifying deep layer ascent in response to more significant
height falls overlapping mid-level divergence, and this will
additionally be aided by increasingly coupled upper jet streaks.
The surface low developing within this impressive ascent will then
deepen as it lifts northeast from Kansas /12Z Saturday/ to Michigan
/12Z Sunday/. This system will become increasingly progressive
through D2, reaching the Canadian Maritimes by 12Z Monday.

This evolution will yield an impressive swath of snow from the
Northern Plains through much of the Midwest and then into the Great
Lakes. As the low develops, increasing warm/moist advection will
surge PWs out of the Gulf, and PW anomalies above the 90th
percentile are progged by NAEFS to reach as far north as MO/IA.
This will occur during a period of intensifying 290K isentropic
ascent, which when occurring beneath the larger scale synoptic lift
will cause snowfall to expand quickly, and become heavy, especially
where 700-600mb fgen intensifies (both due to the WAA and the
ageostrophic response of the upper jet position). At the same time, cross-sections continue to indicate a threat for CSI due to folding
theta-e surfaces, which additionally will support periods of heavy
snowfall rates as laterally translating bands shift northeast
through the region. Snowfall rates of 1-2"/hr are likely (>80%
chance according to the HREF), which, although won't be constant,
will help rapidly accumulate snowfall even with SLRs that will be
around to slightly below climo most of the event.

This intense snowfall will result in widespread significant
impacts, and the WSSI-P indicates a 60-80% chance of major impacts
for parts of IA, IL, and WI, including the Des Moines, Chicago, and
Milwaukee metro areas. This will snarl travel during the busy
post-Thanksgiving holiday weekend. Where snow is the most intense
and longest lasting, record or near-record November snowfall is
possible, especially across eastern IA, southern WI, and northern
IL. This is also where the ECMWF EFI is above 0.9 with an SoT of
1-5, further indicating the potentially record-breaking November
snowfall.

WPC probabilities D1 are high (>70%) for at least 6" of snow from=20
central IA though southern MI, with locally more than 12" possible
(10-30% chance) in eastern IA, southern WI, and northern IL.
Isolated higher totals are possible as well where any banding can
persist due to local convergent features such as indicated by many
of the high-res models near Lake Michigan.

The most significant snowfall should wane quickly from west to east
by 12Z Sunday, but post-system NW flow will create some modest lake
effect snow (LES) across the U.P. and L.P. of MI, as well as east
of Lakes Erie and Ontario Sunday night. Additionally, some modest warm-advection snowfall is likely across the higher terrain of the
interior Northeast before snowfall comes to an end by 12Z Monday.
Additionally snowfall of more than 4 inches is likely (50-90%
chance) according to WPC probabilities from the Chautauqua Ridge
northeast through the higher terrain of the Adirondacks, and into
VT/NH/ME.

Key Messages remain in effect for this system (Key Message 2=20
below).


...Central Rockies through the Ohio Valley...=20
Days 2-3...

The next system follows quickly behind the powerful storm across
the Midwest as progressive flow dominates the CONUS.

This system begins as a positively tilted shortwave emerging from
the Pacific Northwest and then digging rapidly into the Four
Corners states by 12Z Monday. As this impulse dives southeast, the
associated vorticity lobe will swing rapidly east, forcing the
evolution into a neutral tilt over the Central/Southern Plains D3,
and potentially becoming negatively tilted late in the forecast
period across the Mid-Mississippi Valley. During this evolution, a
downstream upper jet streak will amplify and pivot poleward over
the Central Plains to enhance deep layer lift. This should cause an
area of heavy snowfall D2 across the Central Rockies, including=20
the Wasatch, Uintas, and CO Rockies where snow levels of around
4000-5000 ft are expected. Although the system is progressive, PW
anomalies above the 90th percentile will support periods of heavy
snow, aided by upslope into the terrain, and WPC probabilities for
more than 4 inches of snow have increased to 70-90% across the Ruby
Mountains in NV, as well as the expanse of the Wasatch, Uintas, CO
Rockies, and San Juans. Locally as much as 12" of snow is possible
in the highest terrain of Colorado.

The forecast becomes more challenging into D3 as this system=20
pushes east. Although the surface wave is likely to wane across the Southern/Central Plains, the downstream impressive jet streak and=20
height falls invof the upper trough will persist. Late Monday, some
of the guidance indicates that the downstream jet and a secondary=20 sub-tropical jet streak emerging across Mexico will phase, leading=20
to secondary low pressure development across the Mississippi=20
Valley. As this occurs, precipitation will expand from the Gulf=20
Coast through the Mid-Mississippi Valley in response to=20
intensifying moist isentropic ascent along the 290K-300K surfaces.=20
Mixing ratios within this plume are progged at 4-8 g/kg, around the
75th-90th percentile for the date, indicative of the impressive
moisture availability in this system.=20

While there are still important timing, location, and thermal=20
differences among the various global members and their associated=20
ensembles, the trends are for a wetter and colder system which=20
could produce significant snow and mixed precipitation before 12Z=20
Tuesday. The AIFS and ECMWF EFI are both well southeast of the=20
highest NBM probabilities during D3, but the D3/D4 clusters=20
indicate high variability due to timing differences of the trough.=20
Despite this uncertainty, current WPC probabilities for at least 2"
of snow are moderate (30-70% chance) from central Kansas through=20
the western Ohio River Valley, with the potent jet streak aloft=20
helping to produce potential banded snow in this region.=20

Additionally, with warm moist air flooding northward from the Gulf
and a retreating cold high pressure in place, a zone of mixed
precipitation, including freezing rain, is likely from the Ozarks
through the southern Appalachians. There continues to be much
uncertainty in the axis of heaviest ice accretions, but
probabilities for at least some modest ice have come up tonight,
leading to increasing confidence in areas of impactful freezing
rain. At this time, WPC probabilities for 0.1" on D3 are as high as
30% in the Ozarks, and 30-50% in the southern Appalachians.

This system will likely continue beyond this forecast period while strengthening, and may create heavy snow across the interior Mid-
Atlantic and Northeast on Tuesday. For this reason, key messages
have been initiated (Key Message 3 below).


Weiss



...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!9tHzHRjIkt5Wlu4_tiXy9Sv1ZC2dufc5i37Fx8TxUhNW7= OiJVNq0TjnWroPuqfJkGLQTip36UtlIlRHH1vKCqFKDIUk$=20

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!9tHzHRjIkt5Wlu4_tiXy9Sv1ZC2dufc5i37Fx8TxUhNW7= OiJVNq0TjnWroPuqfJkGLQTip36UtlIlRHH1vKCQsKH6jU$=20



$$

=3D =3D =3D
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FOUS11 KWBC 292024
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
324 PM EST Sat Nov 29 2025

Valid 00Z Sun Nov 30 2025 - 00Z Wed Dec 03 2025


...Northern High Plains through the Midwest into the Northeast...=20
Days 1-2...

...Significant winter storm unfolding across the Midwest today...

A pair of 500mb vorticity maximums are interacting with one another
and helping to carve out a negatively-tilted 250-500mb layer trough
over the Midwest this afternoon. A coupled 250mb jet streak setup
is further strengthening the ongoing storm system at the surface,
while at the same time, strong 850-700mb WAA ahead of the storm is
promoting 290K isentropic glide over the Midwest that is fostering
highly saturated profiles within a mesoscale environment that is
ripe for heavy snow bands. ECMWF ensembles show S-SWrly 850mb winds
in excess of 60 kts over the Middle MS Valley, which are topping=20
the 99.5 climatological percentile for late Nov and early Dec. This
exceptional LLJ is feeding a slug of 850-500mb moisture northward=20
that will wrap around the storm system and sufficiently saturate=20
the DGZ over the Midwest. WPC's Snowband Probability Tracker, which
utilizes HREF members, shows a band of 1-2"/hr snowfall rates from
central IA today that heads east across the MS River and towards=20
the Great Lakes this evening.=20

Snow will persist throughout the Great Lakes tonight with snow=20
arriving over the Northeast and central Appalachians Sunday=20
morning. LES bands will develop within broad cyclonic flow off=20
Lakes Superior and Michigan and continue through Sunday evening.
LES bands will stick around a little longer downwind of Lakes Erie
and Ontario but eventually taper off by Monday morning as high
pressure moves in. Locally heavy snowfall is possible in parts of=20
the Tug Hill on Sunday, as well as the White Mountains above
2,000ft where steady SWrly upslope flow within an atmosphere
remaining sub-freezing.=20

WPC probabilities depict moderate-to-hgih chances (50-80%) for
additional snowfall totals >6" along and east of the MS River from
eastern IA and southern MN to the Mitten of Michigan. There are
some low chance probabilities (10-30%) for snowfall totals
exceeding 12" in coastal areas of southeast WI, the Chicagoland
metro area, southwest MI, and northern IN where LES bands may
contribute enough snowfall to where over a foot of snow has
accumulated by the time the LES machine concludes. Downwind of Lake
Erie, parts of the Chautauqua Ridge have moderate chances (40-60%)
for snowfall totals >4" through Monday Sunday night. In the
Northeast, the Tug Hill and White Mountains sport moderate-to-high
chances (50-80%) for snowfall accumulations >6" with localized=20
totals approaching 12" possible by the time this winter storm=20
concludes. The WSSI continues to summarize this storm well,=20
highlighting Moderate to locally Major impacts from central IA on=20
east through the Milwaukee/Chicago metro areas and into northern IN
and southern MI. Expect considerable disruptions to travel in=20
these areas as travelers are likely to encounter numerous travels=20
delays by both road and by air today and lingering through tonight.

Key Messages remain in effect for this system (Key Message 2=20
below).


...Central Rockies through the Ohio Valley, Ice in the Ozarks...=20
Days 2-3...

A positively titled 500mb trough diving south from the Northwest
into the Central Rockies on Sunday will contain both sufficient
synoptic-scale lift and 700-300mb mean layer moisture to support
rounds of mountain snow from central OR and the northern Great
Basin on east across the Wasatch and into the CO Rockies. The
heavier totals in the Great Basin and Wasatch will generally=20
reside above 8,000ft, while the CO/northern NM Rockies are most=20
likely to see their heavier snowfall totals above 9,000ft. WPC=20
probabilities show these listed elevations as having >50% chances=20
for snowfall >8" with localized totals >12" in the peaks of the CO=20 Rockies.=20

As snow continues across the Central Rockies Sunday night, the
aforementioned 500mb trough will begin to eject east into the
Central Plains. A strengthening surge in 700mb WAA and the 500mb=20
PVA will foster a blossoming area of snowfall from the central
Plains to the Middle MS Valley. Snowfall totals are most likely to
range between a coating-3", although WPC probabilities do show low
chances (10-30%) for snowfall totals >4" over northeast KS,
southeast NE, and northern MO through Monday morning. This narrow=20
plume of snow races east across the Lower Great Lakes and OH Valley
Monday evening with similar snowfall totals.

Farther south, as low-level WAA and moisture over-run an air-mass
that features sub-freezing temperatures and dry dew points, a setup
for freezing rain unfolds from the ArkLaTex on across much of AR,
northern MS, western TN, and southern MO. The plume of low-level
moisture does not last too long, but 290K isentropic ascent sticks
around long enough for some disruptive ice accumulations in parts
of these areas on Monday. WPC probabilities show low chances
(10-30%) for ice accumulations over a tenth of and inch, but there
are moderate chances (40-60%) for at least a hundredth of an inch.
The WSSI-P does show up to 40% odds for Minor Impacts as a result
of this freezing rain setup on Monday across much of central AR.=20


...Central Appalachians, Mid-Atlantic, & Northeast...
Day 3-3.5...

...A complex & potentially disruptive winter storm to affect these
regions on Tuesday and into Tuesday night...

Summary: The first accumulating snowfall and disruptive ice event=20
of the season is likely to occur from the Central Appalachians and=20
interior Mid-Atlantic to the Northeast. There remain ongoing=20
changes and disagreements in guidance with snowfall totals, who=20
sees the heaviest totals, and timing all still lower in confidence.
Those in these regions should monitor the forecast from WPC and=20
their local WFOs over the next 24-48 hours.=20

Analysis: As the Central Plains disturbance tracks east Monday=20
evening, there are three other disturbances that are influencing=20
this complicated setup. The first is a weak feature over South TX=20
that is running just out in front of the main upper trough over the
Central Plains. Second: a fast moving 500mb trough over south-=20
central Canada racing southeastward through the Great Lakes by=20
Monday night. Third:the departing system over the Northeast on=20
Monday that races east of Atlantic Canada Monday night. Where=20
guidance is in agreement is that the primary trough over the=20
Central Plains works in tandem with the ejecting Deep South=20
disturbance to direct a plume of 700-300mb moisture at the East=20
Coast. This moisture source will overrun a residual sub-freezing=20
air-mass Monday night over the Central Appalachians and Mid-=20
Atlantic that will support disruptive ice accumulations. However,=20
the dome of high pressure is departing as the storm approaches. For
areas west and north of I-95 in the Mid-Atlantic, boundary layer=20
wet-bulb temperatures will support at least a brief period for=20
accumulating snow. By 18Z Tuesday, a coupling 500mb jet streak=20
setup will support strong vertical ascent aloft that deepens a=20
coastal low as it tracks off the coast. To the north of the storm=20
track, heavy-banded precipitation to the north of a 850-700mb FGEN
band will transpire with snow most likely to occur north of I-95=20
in the higher terrain.

This is where the agreements in the overall setup end. Guidance
members such as the ECMWF show a less amplified Middle MS Valley
feature and less phasing with the Great Lakes disturbance, with
that Great Lakes feature suppressing the storm tracks with its
ensemble membership over the GEFS. Meanwhile, the GEPS are north
and more amplified compared to the GEFS, making the GEFS the
middle ground in storm position. Notably, the EC-AIFS ensemble
means is stronger with the surface low as it reaches the East=20
Coast on Tuesday and its QPF footprint is farther up the coast than
the EPS membership is. At the moment, the ECMWF is on the drier=20
side of guidance, while other like the CMC/NAM are much more=20
amplified. What today's trends have favored, as of this discussion,
is a slightly faster solution that would allow for precipitation=20
to arrive sooner on Tuesday morning.=20

With the cold air-mass retreating on Tuesday, the expectations for
those from northern VA and northern MD on north and east through=20
southeast PA, the Delaware Valley, and into southern New England
was to favor lower SLRs, which should make for a heavy/wet snow.=20
That said, the storm track is critical in determining how far north
the rain/snow line gets. As is the case in marginal boundary layer
temperature environments with fast moving coastal lows that are=20
unable to develop a robust deformation zone, plus baking in=20
climatology for the time of year, it should be the higher=20
elevations north and west of I-95 that are most favored for=20
accumulating snowfall. This setup favors interior New England for=20
heavy snow, although should the Great Lakes disturbance act to=20
suppress the storm track, this could shift farther south to the=20
Catskills and higher terrain of southern New England.=20

WPC probabilities show moderate-to-high chances (50-70%) for=20
snowfall totals >4" from east-central PA on north and east through=20
the Poconos, Catskills, Berkshires, Green, and White Mountains.=20
Farther south, the Philly/Baltimore/DC metro areas may start out=20
briefly as snow, but transition to a wintry mix on Tuesday. There=20
is a possibility for a more icy scenario should cold-air damming=20
(CAD) stick around longer on Tuesday before transitioning to plain
rain. Speaking of CAD, the Central Appalachians will see sub-=20
freezing surface temperatures persist long enough to support a=20
treacherous freezing rain event. WPC probabilities depict=20
moderate-to-high chances (50-80%) for ice accumulations over a=20
tenth of an inch from the Blue Ridge of western NC on north through
the WV/VA Appalachians and Shenandoah Valley with low chances=20
(10-30%) for over a quarter inch of ice. The WSSI-P shows a swath=20
of >50% chances for Minor Impacts from the Central Appalachians on=20
north and east through the WV Panhandle, along and west of Parrs'=20
Ridge in northern MD, through east-central PA, northern NJ, southern
NY, and the interior areas of New England. Key messages are=20
ongoing for this system (Key Message 3 below).=20


Mullinax


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!-II4-v4O3ltIgIqqc2v258ylBcED4sbm6CU-CkNDfY5qL= K4MAm3zknjfJhB255Hjom1Yu-Xc5gaRSOypkDlfvV8Ix70$=20

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!-II4-v4O3ltIgIqqc2v258ylBcED4sbm6CU-CkNDfY5qL= K4MAm3zknjfJhB255Hjom1Yu-Xc5gaRSOypkDlfOJ_EuZY$=20




$$

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FOUS11 KWBC 292040
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
340 PM EST Sat Nov 29 2025

Valid 00Z Sun Nov 30 2025 - 00Z Wed Dec 03 2025


...Northern High Plains through the Midwest into the Northeast...=20
Days 1-2...

...Significant winter storm unfolding across the Midwest today...

A pair of 500mb vorticity maximums are interacting with one another
and helping to carve out a negatively-tilted 250-500mb layer trough
over the Midwest this afternoon. A coupled 250mb jet streak setup
is further strengthening the ongoing storm system at the surface,
while at the same time, strong 850-700mb WAA ahead of the storm is
promoting 290K isentropic glide over the Midwest that is fostering
highly saturated profiles within a mesoscale environment that is
ripe for heavy snow bands. ECMWF ensembles show S-SWrly 850mb winds
in excess of 60 kts over the Middle MS Valley, which are topping=20
the 99.5 climatological percentile for late Nov and early Dec. This
exceptional LLJ is feeding a slug of 850-500mb moisture northward=20
that will wrap around the storm system and sufficiently saturate=20
the DGZ over the Midwest. WPC's Snowband Probability Tracker, which
utilizes HREF members, shows a band of 1-2"/hr snowfall rates from
central IA today that heads east across the MS River and towards=20
the Great Lakes this evening.=20

Snow will persist throughout the Great Lakes tonight with snow=20
arriving over the Northeast and central Appalachians Sunday=20
morning. LES bands will develop within broad cyclonic flow off=20
Lakes Superior and Michigan and continue through Sunday evening.
LES bands will stick around a little longer downwind of Lakes Erie
and Ontario but eventually taper off by Monday morning as high
pressure moves in. Locally heavy snowfall is possible in parts of=20
the Tug Hill on Sunday, as well as the White Mountains above
2,000ft where steady SWrly upslope flow within an atmosphere
remaining sub-freezing.=20

WPC probabilities depict moderate-to-hgih chances (50-80%) for
additional snowfall totals >6" along and east of the MS River from
eastern IA and southern MN to the Mitten of Michigan. There are
some low chance probabilities (10-30%) for snowfall totals
exceeding 12" in coastal areas of southeast WI, the Chicagoland
metro area, southwest MI, and northern IN where LES bands may
contribute enough snowfall to where over a foot of snow has
accumulated by the time the LES machine concludes. Downwind of Lake
Erie, parts of the Chautauqua Ridge have moderate chances (40-60%)
for snowfall totals >4" through Monday Sunday night. In the
Northeast, the Tug Hill and White Mountains sport moderate-to-high
chances (50-80%) for snowfall accumulations >6" with localized=20
totals approaching 12" possible by the time this winter storm=20
concludes. The WSSI continues to summarize this storm well,=20
highlighting Moderate to locally Major impacts from central IA on=20
east through the Milwaukee/Chicago metro areas and into northern IN
and southern MI. Expect considerable disruptions to travel in=20
these areas as travelers are likely to encounter numerous travels=20
delays by both road and by air today and lingering through tonight.

Key Messages remain in effect for this system (Key Message 2=20
below).


...Central Rockies through the Ohio Valley, Ice in the Ozarks...=20
Days 2-3...

A positively titled 500mb trough diving south from the Northwest
into the Central Rockies on Sunday will contain both sufficient
synoptic-scale lift and 700-300mb mean layer moisture to support
rounds of mountain snow from central OR and the northern Great
Basin on east across the Wasatch and into the CO Rockies. The
heavier totals in the Great Basin and Wasatch will generally=20
reside above 8,000ft, while the CO/northern NM Rockies are most=20
likely to see their heavier snowfall totals above 9,000ft. WPC=20
probabilities show these listed elevations as having >50% chances=20
for snowfall >8" with localized totals >12" in the peaks of the CO=20 Rockies.=20

As snow continues across the Central Rockies Sunday night, the
aforementioned 500mb trough will begin to eject east into the
Central Plains. A strengthening surge in 700mb WAA and the 500mb=20
PVA will foster a blossoming area of snowfall from the central
Plains to the Middle MS Valley. Snowfall totals are most likely to
range between a coating-3", although WPC probabilities do show low
chances (10-30%) for snowfall totals >4" over northeast KS,
southeast NE, and northern MO through Monday morning. This narrow=20
plume of snow races east across the Lower Great Lakes and OH Valley
Monday evening with similar snowfall totals.

Farther south, as low-level WAA and moisture over-run an air-mass
that features sub-freezing temperatures and dry dew points, a setup
for freezing rain unfolds from the ArkLaTex on across much of AR,
northern MS, western TN, and southern MO. The plume of low-level
moisture does not last too long, but 290K isentropic ascent sticks
around long enough for some disruptive ice accumulations in parts
of these areas on Monday. WPC probabilities show low chances
(10-30%) for ice accumulations over a tenth of and inch, but there
are moderate chances (40-60%) for at least a hundredth of an inch.
The WSSI-P does show up to 40% odds for Minor Impacts as a result
of this freezing rain setup on Monday across much of central AR.=20


...Central Appalachians, Mid-Atlantic, & Northeast...
Day 3-3.5...

...A complex & potentially disruptive winter storm to affect these
regions on Tuesday and into Tuesday night...

Summary: The first accumulating snowfall and disruptive ice event=20
of the season is likely to occur from the Central Appalachians and=20
interior Mid-Atlantic to the Northeast. There remain ongoing=20
changes and disagreements in guidance with snowfall totals, who=20
sees the heaviest totals, and timing all still lower in confidence.
Those in these regions should monitor the forecast from WPC and=20
their local WFOs over the next 24-48 hours.=20

Analysis: As the Central Plains disturbance tracks east Monday=20
evening, there are three other disturbances that are influencing=20
this complicated setup. The first is a weak feature over South TX=20
that is running just out in front of the main upper trough over the
Central Plains. Second: a fast moving 500mb trough over south-=20
central Canada racing southeastward through the Great Lakes by=20
Monday night. Third:the departing system over the Northeast on=20
Monday that races east of Atlantic Canada Monday night. Where=20
guidance is in agreement is that the primary trough over the=20
Central Plains works in tandem with the ejecting Deep South=20
disturbance to direct a plume of 700-300mb moisture at the East=20
Coast. This moisture source will overrun a residual sub-freezing=20
air-mass Monday night over the Central Appalachians and Mid-=20
Atlantic that will support disruptive ice accumulations. However,=20
the dome of high pressure is departing as the storm approaches. For
areas west and north of I-95 in the Mid-Atlantic, boundary layer=20
wet-bulb temperatures will support at least a brief period for=20
accumulating snow. By 18Z Tuesday, a coupling 500mb jet streak=20
setup will support strong vertical ascent aloft that deepens a=20
coastal low as it tracks off the coast. To the north of the storm=20
track, heavy-banded precipitation to the north of a 850-700mb FGEN
band will transpire with snow most likely to occur north of I-95=20
in the higher terrain.

This is where the agreements in the overall setup end. Guidance
members such as the ECMWF show a less amplified Middle MS Valley
feature and less phasing with the Great Lakes disturbance, with
that Great Lakes feature suppressing the storm tracks with its
ensemble membership over the GEFS. Meanwhile, the GEPS are north
and more amplified compared to the GEFS, making the GEFS the
middle ground in storm position. Notably, the EC-AIFS ensemble
means is stronger with the surface low as it reaches the East=20
Coast on Tuesday and its QPF footprint is farther up the coast than
the EPS membership is. At the moment, the ECMWF is on the drier=20
side of guidance, while other like the CMC/NAM are much more=20
amplified. What today's trends have favored, as of this discussion,
is a slightly faster solution that would allow for precipitation=20
to arrive sooner on Tuesday morning.=20

With the cold air-mass retreating on Tuesday, the expectations for
those from northern VA and northern MD on north and east through=20
southeast PA, the Delaware Valley, and into southern New England
was to favor lower SLRs, which should make for a heavy/wet snow.=20
That said, the storm track is critical in determining how far north
the rain/snow line gets. As is the case in marginal boundary layer
temperature environments with fast moving coastal lows that are=20
unable to develop a robust deformation zone, plus baking in=20
climatology for the time of year, it should be the higher=20
elevations north and west of I-95 that are most favored for=20
accumulating snowfall. This setup favors interior New England for=20
heavy snow, although should the Great Lakes disturbance act to=20
suppress the storm track, this could shift farther south to the=20
Catskills and higher terrain of southern New England.=20

WPC probabilities show moderate-to-high chances (50-70%) for=20
snowfall totals >4" from east-central PA on north and east through=20
the Poconos, Catskills, Berkshires, Green, and White Mountains.=20
Farther south, the Philly/Baltimore/DC metro areas may start out=20
briefly as snow, but transition to a wintry mix on Tuesday. There=20
is a possibility for a more icy scenario should cold-air damming=20
(CAD) stick around longer on Tuesday before transitioning to plain
rain. Speaking of CAD, the Central Appalachians will see sub-=20
freezing surface temperatures persist long enough to support a=20
treacherous freezing rain event. WPC probabilities depict=20
moderate-to-high chances (50-80%) for ice accumulations over a=20
tenth of an inch from the Blue Ridge of western NC on north through
the WV/VA Appalachians and Shenandoah Valley with low chances=20
(10-30%) for over a quarter inch of ice. The WSSI-P shows a swath=20
of >50% chances for Minor Impacts from the Central Appalachians on=20
north and east through the WV Panhandle, along and west of Parrs'=20
Ridge in northern MD, through east-central PA, northern NJ,
southern NY, and interior New England. Key messages are ongoing=20
for this system (Key Message 3 below).=20


Mullinax



...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!_sInBjlekP6pjNLeRE9LcvsU1nax_MbMvx1zivFGkr4Rq= k-U2PID8H1T0KDpJqo1tgG6WZCgot_ZewEEuM12DI18XNw$=20

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!_sInBjlekP6pjNLeRE9LcvsU1nax_MbMvx1zivFGkr4Rq= k-U2PID8H1T0KDpJqo1tgG6WZCgot_ZewEEuM12uPpTWiE$=20



$$

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FOUS11 KWBC 300739
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
239 AM EST Sun Nov 30 2025

Valid 12Z Sun Nov 30 2025 - 12Z Wed Dec 03 2025


...Great Lakes to the Interior Northeast...
Day 1...

The major winter storm plaguing the Upper Midwest will wane as the
parent shortwave de-amplifies into a positive tilt and becomes more
embedded in the westerlies across Canada. This will cause a more
rapid progression of the driving low pressure, leading to moderate
continued snow accumulations across the Great Lakes, and expanding
across the higher terrain of the interior Northeast.

The surface low is progged to track from the L.P. of Michigan this
morning into the Canadian Maritimes by Monday morning /end of D1/.
This will result in two areas of additional snowfall accumulation.=20

The first is expected across the Great Lakes as NW flow develops in
the wake of the surface low. While brief deformation snow is likely
as the low departs Michigan, most of the additional snowfall is
likely to be of the lake effect snow (LES) variety as CAA
strengthens across the lakes. 850mb temps falling to -10C or lower
will support steep lapse rates and inversion depths rising to
around 800mb to support at least a brief period of heavy LES with
rates exceeding 1"/hr (40-60% chance from the HREF). The most
likely belts of heavy LES D1 will be across the eastern U.P., the
northern L.P., SW MI, and then east of Lake Ontario. In these
areas, WPC probabilities are 50-70% for more than 4 inches, with=20
locally as much as 8 inches east of Lake Ontario.

The other area of heavy snow from this system will be across the
higher terrain of Upstate NY and Northern New England. WAA
expanding northward downstream of the surface low will spread into
Canada, drawing a narrow column of moisture from the Gulf to cause
expanding precipitation in New England. The WAA is impressive but
transient, and regional forecast soundings suggest persistent mid-
level dry air which will somewhat preclude precipitation rate
intensity. Additionally, the cold high pressure over the region
early will rapidly retreat east, leading to funneled southerly=20
flow with no cold air entrenchment. This suggests that the heaviest
snow will be confined only to the higher terrain of the=20
Adirondacks, Greens, and Whites, where WPC probabilities are=20
moderate (30-50%) for 4+ inches of snowfall.


...Central Rockies/Four Corners...
Days 1-2...

A closed 500mb low dropping out of the Interior Northwest will move progressively southeast today while opening into a positively
tilted trough. The base of this feature will reach the Four Corners
Monday morning before continuing to eject into the Central Plains,
and the overlap of height falls with an amplifying jet streak will
produce large scale ascent across the Central Rockies and Four
Corners today. Available moisture is somewhat scarce (PWs only
around 0.25" and around the 10th percentile according to NAEFS) but
the impressive, albeit transient, deep layer lift will overcome
that to produce a swath of heavy snowfall. Snow should begin across
the Great Basin this morning, but intensify in response to better
lift aided by upslope flow over the Wasatch/Uintas this afternoon,
and then the CO Rockies/San Juans/Sangre de Cristos this evening
and tonight. Snow should end early Monday morning. WPC=20
probabilities suggest a high risk (>80% chance) of more than 6=20
inches across most of these mountain ranges, with snow levels=20
generally 4000-5000 ft.



...Central Plains & Ozarks through the Northeast...
Days 2-3...

...Widespread impactful snow and ice likely, but uncertainty with
respect to timing and track remains...

A complex evolution of mid-level features will create the first
widespread winter precipitation event from the Ohio Valley into the Appalachians, Mid-Atlantic, and Northeast. However, uncertainty
remains considerable at this time range and model guidance
continues to feature a variety of solutions which will affect the
accompanying impacts.

This system will develop initially in response to a shortwave
diving out of the Central Rockies Monday afternoon, and this
feature is expected to become neutrally tilted as vorticity lobes
swing through its base by the time it reaches the Ohio Valley
Tuesday morning. Thereafter, the shortwave tracks rapidly east
while maintaining its modest amplitude, exiting New England by 12Z
Wednesday. The global guidance has come into much better agreement
this morning with the progged evolution, maintaining a flatter and
faster wave, and in general, this upper pattern does not=20
conceptually support a widespread significant snowfall.=20

However, there are caveats that may make this a bit more=20
impressive than it would otherwise appear at 500mb. This is=20
primarily due to the amplification and phasing of upper jet=20
streaks: one amplifying downstream of the shortwave and a second=20
subtropical jet streak emerging from Mexico. The interaction of
this jet energy is progged to occur across the Mid-Mississippi
Valley Monday night, with the strengthening result then arcing
poleward through Tuesday to provide more impressive lift both
through the RRQ and LFQ. The strengthening jet streak will provide
sufficient upper ventilation, in conjunction with the mid-level
height falls, to produce surface cyclogenesis along the Gulf Coast
Tuesday morning, with this low then deepening as it tracks rapidly
northeast to off the coast of the Carolinas and then towards the
40/70N benchmark. The SLP trends of the various ensemble camps=20
have been for a faster solution with also some latitudinal gain,=20
suggesting this will not be a heavy snow event for the I-95=20
corridor, which is supported by an unfavorable surface high=20
position as well, but could still cause impactful wintry=20
precipitation across a large area.

As the synoptics intensify and the surface low moves east,
increasing WAA on a 30-50 kts 850mb LLJ will spread northward
leading to an expansion of precipitation. Where this interacts with
the strengthening jet streak, a stripe of heavy banded
precipitation is likely, which will fall as snow in many areas.=20

The first band is expected Monday into Monday night from the=20
Central Plains through the Ohio Valley where the ageostrophic=20
response to the LFQ of the upper jet will help intensify 700-600mb=20
fgen, crossing directly the deepening DGZ (SREF DGZ 50mb depth=20
probabilities > 50%). This should produce a stripe of heavy snow
rates from KS through the Ohio Valley, and although the band will
be progressive, WPC probabilities indicate a moderate risk (50-70%
chance) for at least 2 inches from central KS through eastern OH,
with locally higher amounts of 4+ inches possible (10-30%) aided by
fluffy SLRs. South of this band, increasing moist isentropic=20
ascent atop the retreating cold air will result in an axis of=20
freezing rain across the Ozarks where WPC probabilities are modest
(10-30%) for at least 0.1" of ice accretion, highest in central AR.

Then, during D3 /12Z Tue to 12Z Wed/ the moist isentropic ascent
maximizes leading to widespread heavy precipitation along and ahead
of the strengthening low pressure system. With the surface high
retreating and a lack of mid-level confluence to lock in cold air,
many areas of the Mid-Atlantic into the Northeast will begin as a
brief period of mixed precip, but should quickly change to rain
Tuesday morning, especially along and east of I-95. Inland,
however, the strong WAA, especially in the 850-700mb layer, will=20
result in front end heavy snow, most likely from Kentucky northeast
into interior New England. There is still uncertainty into how far
north the warm air will spread to cause changeover, but=20
significant snow accumulations are likely as reflected by WPC
probabilities that have increased, and now suggest a greater than
70% chance for 4+ inches of snow from the Poconos through Downeast
Maine. Locally more than 8 inches is possible, most likely in the
higher terrain of central New England. It is prudent to note that=20
while most of the guidance does not support an I-95 snow event, the
ECMWF AIFS ensemble, and even to some degree the EFI, suggest some
heavier snow farther south than most of the other camps, which=20
could bring more impactful weather to I-95 and is worth continuing=20
to monitor.

Finally, south of the heavy snow and across the terrain of the
Southern and Central Appalachians, a period of light to moderate
freezing rain is likely which could cause impactful ice
accretions, especially in the higher terrain. Current WPC
probabilities are as high as 30-50% for 0.1" of ice, with local
amounts approaching 0.25" possible in the vicinity of the Blue
Ridge of NC and VA.

Key Messages remain in effect for this system and are linked below
(Key Message #3)


Weiss


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!_c96Fsm1kuyRpsYRqexGYrwZpDlGi30W0sU9cwbGm13v6= 4qFD27sEGEjMb_FSIQmd90IuTeJ7bqYRbSGk1Vc1yHTKf4$=20



$$

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FOUS11 KWBC 302021
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
321 PM EST Sun Nov 30 2025

Valid 00Z Mon Dec 01 2025 - 00Z Thu Dec 04 2025


...Great Lakes to the Interior Northeast...
Day 1...

The storm system responsible for the heavy and disruptive snowfall
that blanketed the Midwest and Great Lakes is tracking into Ontario
this afternoon. Cyclonic flow and CAA within WNW-NW winds will
reinvigorate the LES machine across the Upper Great Lakes, snow
belts of western MI and northern IN, and typical snow belts to the
east of Lakes Erie and Ontario. Snow bands will be capable of
producing anywhere between 1-2"/hr snowfall rates due to the
favorably unstable low-level profiles and a pivoting 850-700mb
trough over head this evening. WPC probabilities show moderate
chance probabilities (40-60%) for additional snowfall totals >4"=20
over far northwest PA and across the Tug Hill. An additional 1-4"
of snow is forecast in the Green and White Mountains before
tapering off by early Monday morning.


...Central Rockies/Central Plains/Mid-South/OH Valley...
Days 1-2...

A 500mb positiviely-tilted trough is tracking through UT today and
will head for the CO/NM Rockies by early Monday morning. The
combination of height falls with a strengthening jet streak will=20
produce large scale ascent across the Central Rockies and Four=20
Corners today and into tonight. Heavy snowfall will be primarily
confined to the >10,000ft peaks of the CO/NM Rockies, although some minor-to-moderate accumulations between 7,000-10,000ft are
possible.=20

As the upper trough tracks east towards the Central Plains tonight,
healthy 500mb PVA coupled with a strengthening 250mb jet streak
will foster healthy synoptic-scale divergence aloft. Guidance also
shows a strengthening 850-700mb WAA regime and corresponding 290K
isentropic ascent over the Central Plains that is likely to result
in a band of moderate-to-heavy snow tracking from northern KS early
Monday morning and across the heart of the Midwest by Monday
afternoon. Temperatures are cold enough aloft to support fluffy
SLRs (>15:1 in most cases) and it is progressive. WPC probabilities
show most accumulations will range between 1-4", given WPC
probabilities for >4" are low (10-30% at most in northeast
KS/northwest MO). However, there are some guidance members that
depict some localized totals >4" by the time the band of snow exits
to the east Monday evening. The same mechanism producing snow in=20
the Central Plains heads for the OH Valley and western PA. Snowfall accumulations will generally range between 1-4" through Tuesday=20
morning.=20

Farther south, as low-level WAA and Gulf moisture spreads over and
air-mass that features sub-freezing temperatures and dry
dewpoints, freezing rain is expected to unfold from the
ArkLaTex eastward across central and southern AR and into western
TN. the plume of low-level moisture does not last long, but 290K
isentropic ascent sticks around long enough for some disruptive=20
ice accumulations in these areas on Monday. WPC probabilities show=20
low chances (10-30%) for ice accumulations than one-tenth of an=20
inch, but there are moderate chances (40-60%) for ice=20
accumulations over one-hundreth in central AR. The WSSI shows a=20
large swath of Minor Impacts across central AR and as far north as=20
the MO/AR border, but some localized Moderate Impacts in central AR
are possible.=20


...Central Appalachians & Northeast...
Days 2-3...

...Widespread hazardous snow and ice to blanket portions of the
Mid-Atlantic and Northeast Monday night and through Tuesday...

By Monday evening, the 500mb trough producing periods of snow over
the OH Valley will track across the Middle MS Valley Monday night
with a secondary disturbance tracking south of it towards the
Southeast. As a third disturbance approaches from the Great Lakes,
a strengthening 250mb jet streak over the Northeast will work with
a second 250mb jet streak over the South to creating a classic
"coupling jet streak" setup off the Mid-Atlantic coast. This will
be the basis for a strengthening winter storm that tracks initially
through the Southeast Monday night and up the East Coast by Tuesday
afternoon.

The primary ingredients are generally agreed upon on all guidance,
although how they come together and where the storm tracks is=20
still coming into focus. High pressure over the Northeast will=20
initially provide a sufficiently cold air-mass to support wintry=20 precipitation at the onset from the Central Appalachians on north=20
and east, but it will be exiting off Atlantic Canada on Tuesday. As
925-700mb WAA advances north Monday night and into Tuesday, any=20
initial snow over the Central Appalachians will changeover to a=20 sleet/freezing rain mix, then all freezing rain. Cold air damming=20
(CAD) will linger long enough in the higher terrain to support=20
disruptive ice accumulations that result in slick travel conditions
Monday night and into Tuesday morning. WPC probabilities show >50%
chances for ice accumulations over a tenth of an inch from the=20
Blue Ridge of western NC on north through the mountains of western=20
VA and eastern WV. There are some low-chance probabilities (10-30%)
for over a quarter inch of ice from VA's Skyline Drive on south and west
to the WV/VA border. The latest WSSI does depict Minor to Moderate
Impacts in these regions with a focus on treacherous travel=20
conditions.

Farther north over the Mid-Atlantic, precipitation is likely to
start out as snow over northern VA/MD, southern PA, and on north
towards the NYC metro Tuesday morning. Guidance then begins to
disagree on the handling of the transition and northward expansion
of the snow-wintry mix area. Low-level SErly flow is strong enough
to where most areas along I-95 should flip over to plain rain on
Thursday morning, but farther inland over the Piedmont of VA,
northern MD, and Lower Susquehanna Valley, low-lvel cold may stick
around long enough for a wintry mix to hang around longer. This is
likely to be the region's first accumulating snowfall, so there are
likely to detrimental impacts to travel even if snowfall and ice
accumulations are minor (1-3" of snow for these areas, up to a=20
tenth of an inch of ice in western MD and northwest VA). However,=20
from the Lehigh Valley and Poconos on north and east through=20
northwest NJ, the Catskills, and into interior southern New=20
England, snow is likely to remain the primary precip type.

The storm by Tuesday afternoon will begin to develop a closed lower
over the Delaware Valley that deepens south of Long Island by
Tuesday evening. To the north and east of the 850mb low, a
consolidated 850-700mb FGEN area will develop and result in a band
of heavy snow somewhere from northeast PA and southern NY (north of
NYC) through southern New England. Snowfall rates within this band
are likely to at least top 1"/hr. There still remains some
uncertainty on where this band sets up, but probabilistic guidance
is showing increase odds on a snowfall swath of >6" from the
Poconos and Catskills on north and east. The higher terrain across
New England (Berkshires, Worcester Hills, Green, Whites, Downeast
Maine) are the most favored for locally heavy snowfall as WPC=20
probabilities shows low-to-moderate chances (30-50%) for over 12"=20
in some spots. The latest WSSI does depict Moderate Impacts due to
snow from western MA and northern CT to southern NH and southern=20
ME with locally Major Impacts possible.=20

In summary, this is going to be the first accumulating snow of the
season for many areas from southern PA to areas just west of I-95,
potentially including the Boston metro area should more southern
guidance come to fruition. Expect travel delays on Tuesday and into
Tuesday night in affected areas. High pressure and dry conditions
return to the Northeast by early Wednesday morning.=20

Key Messages remain in effect for this system and are linked below
(Key Message #3)


Mullinax


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!8j1a6fpP7PIestX6LxHG47zf9CWUftnDL_uYhqq5y-hZB= QnAJRuMy4jSvIskYFi6EXdf5gXbLAYOTj_7E-hkDpvbjsY$=20



$$

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FOUS11 KWBC 302029
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
329 PM EST Sun Nov 30 2025

Valid 00Z Mon Dec 01 2025 - 00Z Thu Dec 04 2025


...Great Lakes to the Interior Northeast...
Day 1...

The storm system responsible for the heavy and disruptive snowfall
that blanketed the Midwest and Great Lakes is tracking into Ontario
this afternoon. Cyclonic flow and CAA within WNW-NW winds will
reinvigorate the LES machine across the Upper Great Lakes, snow
belts of western MI and northern IN, and typical snow belts to the
east of Lakes Erie and Ontario. Snow bands will be capable of
producing anywhere between 1-2"/hr snowfall rates due to the
favorably unstable low-level profiles and a pivoting 850-700mb
trough over head this evening. WPC probabilities show moderate
chance probabilities (40-60%) for additional snowfall totals >4"=20
over far northwest PA and across the Tug Hill. An additional 1-4"
of snow is forecast in the Green and White Mountains before
tapering off by early Monday morning.


...Central Rockies/Central Plains/Mid-South/OH Valley...
Days 1-2...

A 500mb positiviely-tilted trough is tracking through UT today and
will head for the CO/NM Rockies by early Monday morning. The
combination of height falls with a strengthening jet streak will=20
produce large scale ascent across the Central Rockies and Four=20
Corners today and into tonight. Heavy snowfall will be primarily
confined to the >10,000ft peaks of the CO/NM Rockies, although some minor-to-moderate accumulations between 7,000-10,000ft are
possible.=20

As the upper trough tracks east towards the Central Plains tonight,
healthy 500mb PVA coupled with a strengthening 250mb jet streak
will foster healthy synoptic-scale divergence aloft. Guidance also
shows a strengthening 850-700mb WAA regime and corresponding 290K
isentropic ascent over the Central Plains that is likely to result
in a band of moderate-to-heavy snow tracking from northern KS early
Monday morning and across the heart of the Midwest by Monday
afternoon. Temperatures are cold enough aloft to support fluffy
SLRs (>15:1 in most cases) and it is progressive. WPC probabilities
show most accumulations will range between 1-4", given WPC
probabilities for >4" are low (10-30% at most in northeast
KS/northwest MO). However, there are some guidance members that
depict some localized totals >4" by the time the band of snow exits
to the east Monday evening. The same mechanism producing snow in=20
the Central Plains heads for the OH Valley and western PA. Snowfall accumulations will generally range between 1-4" through Tuesday=20
morning.=20

Farther south, as low-level WAA and Gulf moisture spreads over and
air-mass that features sub-freezing temperatures and dry
dewpoints, freezing rain is expected to unfold from the
ArkLaTex eastward across central and southern AR and into western
TN. the plume of low-level moisture does not last long, but 290K
isentropic ascent sticks around long enough for some disruptive=20
ice accumulations in these areas on Monday. WPC probabilities show=20
low chances (10-30%) for ice accumulations than one-tenth of an=20
inch, but there are moderate chances (40-60%) for ice=20
accumulations over one-hundreth in central AR. The WSSI shows a=20
large swath of Minor Impacts across central AR and as far north as=20
the MO/AR border, but some localized Moderate Impacts in central AR
are possible.=20


...Central Appalachians & Northeast...
Days 2-3...

...Widespread hazardous snow and ice to blanket portions of the
Mid-Atlantic and Northeast Monday night and through Tuesday...

By Monday evening, the 500mb trough producing periods of snow over
the OH Valley will track across the Middle MS Valley Monday night
with a secondary disturbance tracking south of it towards the
Southeast. As a third disturbance approaches from the Great Lakes,
a strengthening 250mb jet streak over the Northeast will work with
a second 250mb jet streak over the South to creating a classic
"coupling jet streak" setup off the Mid-Atlantic coast. This will
be the basis for a strengthening winter storm that tracks initially
through the Southeast Monday night and up the East Coast by Tuesday
afternoon.

The primary ingredients are generally agreed upon on all guidance,
although how they come together and where the storm tracks is=20
still coming into focus. High pressure over the Northeast will=20
initially provide a sufficiently cold air-mass to support wintry=20 precipitation at the onset from the Central Appalachians on north=20
and east, but it will be exiting off Atlantic Canada on Tuesday. As
925-700mb WAA advances north Monday night and into Tuesday, any=20
initial snow over the Central Appalachians will changeover to a=20 sleet/freezing rain mix, then all freezing rain. Cold air damming=20
(CAD) will linger long enough in the higher terrain to support=20
disruptive ice accumulations that result in slick travel conditions
Monday night and into Tuesday morning. WPC probabilities show >50%
chances for ice accumulations over a tenth of an inch from the=20
Blue Ridge of western NC on north through the mountains of western=20
VA and eastern WV. There are some low-chance probabilities (10-30%)
for over a quarter inch of ice from VA's Skyline Drive on south and west
to the WV/VA border. The latest WSSI does depict Minor to Moderate
Impacts in these regions with a focus on treacherous travel=20
conditions.

Farther north over the Mid-Atlantic, precipitation is likely to
start out as snow over northern VA/MD, southern PA, and on north
towards the NYC metro Tuesday morning. Guidance then begins to
disagree on the handling of the transition and northward expansion
of the snow-wintry mix area. Low-level SErly flow is strong enough
to where most areas along I-95 should flip over to plain rain on
Thursday morning, but farther inland over the Piedmont of VA,
northern MD, and Lower Susquehanna Valley, low-lvel cold may stick
around long enough for a wintry mix to hang around longer. This is
likely to be the region's first accumulating snowfall, so there are
likely to detrimental impacts to travel even if snowfall and ice
accumulations are minor (1-3" of snow for these areas, up to a=20
tenth of an inch of ice in western MD and northwest VA). However,=20
from the Lehigh Valley and Poconos on north and east through=20
northwest NJ, the Catskills, and into interior southern New=20
England, snow is likely to remain the primary precip type.

The storm by Tuesday afternoon will begin to develop a closed lower
over the Delaware Valley that deepens south of Long Island by
Tuesday evening. To the north and east of the 850mb low, a
consolidated 850-700mb FGEN area will develop and result in a band
of heavy snow somewhere from northeast PA and southern NY (north of
NYC) through southern New England. Snowfall rates within this band
are likely to at least top 1"/hr. There still remains some
uncertainty on where this band sets up, but probabilistic guidance
is showing increase odds on a snowfall swath of >6" from the
Poconos and Catskills on north and east. The higher terrain across
New England (Berkshires, Worcester Hills, Green, Whites, Downeast
Maine) are the most favored for locally heavy snowfall as WPC=20
probabilities shows low-to-moderate chances (30-50%) for over 12"=20
in some spots. The latest WSSI does depict Moderate Impacts due to
snow from western MA and northern CT to southern NH and southern=20
ME with locally Major Impacts possible.=20

In summary, this is going to be the first accumulating snow of the
season for many areas from southern PA to areas just west of I-95,
potentially including the Boston metro area should more southern
guidance come to fruition. Expect travel delays on Tuesday and into
Tuesday night in affected areas. High pressure and dry conditions
return to the Northeast by early Wednesday morning.=20

Key Messages remain in effect for this system and are linked below
(Key Message #3)


Mullinax



...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!4a3u3xvT3-hHMgEuVV19WxvIhLYs9AwNztPM6v7_Rvx-N= fA7rqvdw0CdltnXbH7K29K2qwndPvJ_PXi1VPNvhwlFOkk$=20



$$

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FOUS11 KWBC 010804
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
304 AM EST Mon Dec 1 2025

Valid 12Z Mon Dec 01 2025 - 12Z Thu Dec 04 2025


...Central Plains through the Mid-Atlantic & Northeast...=20
Days 1-3...

...Widespread moderate to heavy snow from the Central Plains to the
Northeast will impact travel early this week while treacherous
icing occurs across the Appalachians...

A potent but positively tilted mid-level shortwave trough will be
advancing eastward from the Four Corners to start the period /12Z
today/ and move progressively eastward into the Ohio Valley by
Tuesday morning. During this translation, the feature, while
remaining of modest amplitude, may take on at least a neutral tilt
as vorticity continues to swing through the base of the
accompanying parent trough, and the entire system should be off the
New England Coast by 12Z Wednesday with only subtle amplification
expected. Although this shortwave will remain modest overall, the
accompanying jet streaks, both a downstream intensifying feature
and the broader subtropical jet lifting out of Mexico, are expected
to phase across the southern/central Plains today. The increasing
ascent left by the resulting RRQ overlapping height falls from the
shortwave will result in surface cyclogenesis along the Gulf Coast
tonight. This surface low is then expected to track rapidly
northeast across the southern Mid-Atlantic states and then deepen
just inside the 40N/70W Benchmark Tuesday night before lifting into
into the Canadian Maritimes.

This evolution will result in widespread snow and freezing rain
across the eastern half of the country, with two distinct areas of
impactful wintry precipitation.

On the north side of this system, a swath of moderate snow is
expected on D1 from Kansas through the Ohio Valley. This is in
response to the strengthening/phased jet streak which will begin to
tilt poleward to support impressive upper diffluence. At the same
time, some mid-level frontogenesis will be intensified by this jet
streak, forcing favorable overlap of ascent into the deepening DGZ
(SREF probabilities for 100mb of depth over 30% now) which will
support heavy snowfall rates within a translating band of 1"/hr or
more at times, aided by fluffy SLRs. The guidance has trended=20
upward with this feature, and WPC probabilities indicate a 10-30%
chance for at least 4 inches of snow from near Kansas City through
just south of Chicago.


As this band moves east into the Ohio Valley, it will become=20
merged with the larger system developing near the Gulf as=20
impressive moist isentropic ascent begins and lifts a theta-e ridge
northward to expand the precipitation shield. The strong 850mb WAA
will provide additional ascent, with the accompanying fgen serving
to intensify omega into the DGZ. While the WAA will likely result=20
in a burst of moderate snowfall in many areas from the Mid-
Atlantic/Ohio Valley northeast, a lack of resupplying cold air as=20
the surface high retreats will enable a quick transition to=20
mixed/rain, especially along and east of I-95 between VA and MA.=20
However, NW of the I-95 corridor, a prolonged period of moderate to
at times heavy snow is likely, with 1+"/hr rates spreading from PA
to ME. This will create an axis of snowfall for which WPC=20
probabilities indicate a high risk (>70% chance) for 4+ inches from
the Poconos through Downeast Maine, with locally as much as 8-12=20
inches possible (50% chance) from the Berkshires through the=20
Monadnock region of NH and into southern ME.

It is important to add as well, that despite what should be a
relatively quick transition from snow to mix to rain along I-95,
the Tuesday morning commute could be significantly impacted.

South of the heavy snow axes, two areas of impactful freezing rain
are also anticipated. The first will be across portions of
AR/MO/KY, in the vicinity of the Ozarks on Monday morning as
isentropic ascent and the accompanying moisture plume spread
precipitation into this region. Initially, surface wet-bulb
temperatures will be sub-freezing, so precipitation will fall as
freezing rain in response to the warm nose pivoting overhead.
However, this p-type should generally be short lived except in the
coldest regions, and WPC probabilities for 0.1" of ice peak around
30% in central AR.

More significant icing is likely across portions of the central and
southern Appalachians as isentropic ascent and accompanying WAA
intensify Monday night into Tuesday. Here, wet-bulb temperatures
will again be below freezing leading to an extended period of
freezing rain from SW NC into western MD. Although the high
retreats, this cold air may be more challenging to scour out,
especially in the higher elevations, leading to an extended period
of freezing rain with impactful ice accretions likely. WPC
probabilities D1 into D2 suggest a high risk (>70%) for at least
0.1" of icing from western NC through the Shenandoah region of VA,
with a low chance (10-30%) of up to 0.25" in isolated locations.

Key Messages remain in effect for this system and are linked below
(Key Message #3)


...Northern to Southern Rockies...=20
Days 2-3...

A shortwave digging out of British Columbia embedded within broad
cyclonic flow across the eastern half of the CONUS will spread
increasing synoptic ascent across the Intermountain West beginning
Tuesday morning. This shortwave will move progressively southeast
Tuesday, and may become more amplified despite maintaining a strong
positive tilt by Wednesday morning in response to secondary
vorticity maxima digging through its base. This will result in a
slowing and amplification of the trough, with downstream ascent
maximizing through height falls, PVA, and downstream intensifying
jet energy.=20

Available moisture will generally be modest as reflected by near-
normal PW anomalies, but the overlapped synoptic lift will be more
than sufficient to wring this out as periods of moderate to heavy
snowfall across much of the terrain. At the same time, a wave of
low pressure is progged to drop southeast coincident with the
shortwave trough, and a secondary front will also push south out of
Canada to cool the column while additionally leading to localized
upslope flow. Despite a shallow DGZ noted in regional forecast
soundings, the best ascent may maximize within this snow growth
region to enhance snowfall, and this suggests a broad swath of
moderate snow is likely Tuesday and Wednesday across much of the
Rockies.

WPC probabilities for 4+ inches D2 are highest from MT through WY,
with local maxima in snowfall above 8 inches possible across the
Little Belts and Absarokas, with snow levels running around
2000-3000 ft. By D3, the heaviest snow pivots southeast reaching
the CO Rockies, the San Juans, and Sangre de Cristos, where WPC
probabilities indicate a moderate risk (50-70%) for 6+ inches of
snowfall. Snow levels continue to fall on Wednesday as well such
that even the I-25 urban corridor from Cheyenne to Santa Fe may
experience a few inches of snow, with the higher accumulations
expected across the Raton Mesa and Palmer Divide.


...Great Lakes & Northeast...
Day 3...

A strong arctic front will race across the Great Lakes Wednesday,
likely reaching Upstate NY by Thursday morning before continuing
into New England beyond this forecast period. While confidence is
low at this time, the signals appear favorable for snow squalls
along this front as it dives southeast. The trends in the GFS SnSq
parameter have decayed a bit in recent runs, but the environment at
this time frame appears at least marginally favorable for a line,
or lines, of convective snow showers/snow squalls Wednesday into
Thursday. While snowfall amounts will be minimal, snow squalls can
cause dangerous driving due to briefly heavy snow rates and gusty
winds, so this event will need to be monitored as it gets closer.


Weiss



...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!5yQB3jpQNoHGi7CLwb89D4XfQqfQD6y2WYs0GA0deyuOX= 5XM7r-Hwq9HUl0fa45gZku1edttTkTaRH-BsCW62nKKERs$=20



$$

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FOUS11 KWBC 012030
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
330 PM EST Mon Dec 1 2025

Valid 00Z Tue Dec 02 2025 - 00Z Fri Dec 05 2025


...Central Plains through the Mid-Atlantic & Northeast...=20
Days 1-2...

...Widespread moderate to heavy snow from the Central Plains to the
Northeast will impact travel early this week while treacherous
icing occurs across the Appalachians...

A positively-tilted upper trough will continue to move steadily
east of the Rockies, assuming a neutral tilt, with phasing streams
over the Plains early in the period. This trough will continue to=20
move east across the Midwest on Tuesday, reaching the East Coast=20
late in the day, before becoming negatively-tilted as it moves off=20
of the Mid Atlantic/Northeast coasts Tuesday night.=20

At the surface, low pressure will develop over the northern Gulf=20
tonight before energy transfers to low pressure along the=20
Southeast coast. Supported by a coupled upper jet, this low will=20
deepen quickly as it tracks north along the Mid Atlantic to the=20
Northeast coast on Tuesday. With the 12Z ECMWF now shifted north,=20
the general consensus of the deterministic runs and the ensemble=20
means show the low tracking near the 40N/70W benchmark around 00Z=20
Wednesday before continuing on a track east of the Canadian=20
Maritimes Wednesday morning.

Upper level forcing along with low-to-mid level frontogenesis will
continue to support light to moderate snow spreading east from the
mid Mississippi through the Ohio valleys tonight, with the latest=20
WPC probabilities indicating that accumulations for most areas will
remain under 4 inches.

As this band moves east into the Ohio Valley, it will merge with=20
the larger system developing near the Gulf as impressive moist=20
isentropic ascent supports a north-moving theta-e ridge and an=20
expanding precipitation shield. Strong 850mb WAA will provide=20
additional ascent, with the accompanying frontogenesis serving to=20
intensify omega into the DGZ. While the WAA will likely result in a
burst of moderate snowfall in many areas across the interior Mid=20
Atlantic into the Northeast, a lack of resupplying cold air as a=20
surface high to the north retreats will enable a quick transition=20
to mixed/rain, especially along and east of the I-95 corridor from
northern Virginia to Boston. The 12Z models trended slightly=20
warmer, further indicating that areas from DC to NYC will be=20
mostly, if not entirely, all rain. However, northwest of the I-95=20
corridor, the story remains much different, where a prolonged=20
period of moderate, to at times heavy snow, is likely, with 1+"/hr=20
rates spreading from Pennsylvania to Maine. This will create an=20
axis of snowfall for which WPC probabilities continue to show a=20
high risk (>70% chance) for 4+ inches from the Poconos through=20
Downeast Maine, with locally as much as 8-12 inches possible (50%=20
chance) across parts of the Catskills and from the Berkshires to=20
southern Maine, including the northern Worcester Hills and=20
Monadnock region.

South of the heavy snow axes, light ice accumulations will shift
northeast from southern Arkansas into eastern Tennessee and=20
Kentucky. WPC probabilities indicate that where ice does
accumulate it will remain under 0.10 inch for most areas.

Meanwhile, more significant icing is likely to develop starting=20
tonight across portions of the central and southern Appalachians as
isentropic ascent and accompanying WAA intensify. Subfreezing wet-
bulb temperatures will support an extended period of freezing rain
along the southern to central Appalachians from North Carolina to=20
western Maryland. Although the high to the north will be=20
retreating, this cold air may be more difficult to scour out,=20
especially in the more sheltered locations, leading to an extended=20
period of freezing rain with impactful ice accretions likely. WPC=20 probabilities show 50 percent or greater probabilities for at least
0.1 inch of ice from across parts of western North Carolina=20
northward along the southern Blue Ridge into southern West Virginia
and the Shenandoah region of Virginia, with a low chance (10-30%)=20
of up to 0.25 inch in isolated locations.

Key Messages remain in effect for this system and are linked below
(Key Message #3)


...Northern to Southern Rockies...=20
Days 1-3...

A shortwave will dig south out of British Columbia into the
northwestern U.S. overnight. This shortwave will continue to move=20
southeast Tuesday into Wednesday, and may become more amplified as
it drops through the Great Basin in response to secondary=20
vorticity maxima digging through its base. This will result in a=20
slowing and amplification of the trough, with downstream ascent=20
maximizing through height falls, PVA, and downstream intensifying=20
jet energy.=20

Available moisture will generally be modest as reflected by near-
normal PW anomalies, but the overlapped synoptic lift will be more
than sufficient to wring this out as periods of moderate to heavy
snowfall across much of the terrain. At the same time, a wave of
low pressure is progged to drop southeast coincident with the
shortwave trough, and a secondary front will also push south out of
Canada to cool the column while additionally leading to localized
upslope flow. Despite a shallow DGZ noted in regional forecast
soundings, the best ascent may maximize within this snow growth
region to enhance snowfall, and this suggests a broad swath of
moderate snow is likely Tuesday and Wednesday across much of the
Rockies.

WPC probabilities for 4+ inches Day 1 are highest from northwestern
Montana to northwestern Wyoming and northern Idaho, with local=20
maxima in snowfall above 8 inches possible across the higher
terrain. By Day 2, the heaviest snow pivots southeast reaching the
central Rockies, notably the Colorado ranges, where most of the
higher probabilities for accumulations above 4 inches are=20
centered. The southern shift is expected to continue into Day 3,=20
with the Sangre de Cristos in northern New Mexico the focus for the
higher probabilities for amounts over 4 inches.

...Great Lakes & Northeast...
Day 3...

A strong arctic front will race across the Great Lakes Wednesday,
likely reaching Upstate NY by Thursday morning before continuing
into New England. The signals appear favorable for snow squalls=20
along this front as it dives southeast. The trends in the GFS SnSq=20
parameter remain fairly muted, however the NAM ramps up notably
across parts of Pennsylvania and Upstate NY into New England on
Thursday. While snowfall accumulations will be minimal, snow=20
squalls can cause dangerous driving due to briefly heavy snow rates
and gusty winds, so this event will need to be monitored as it=20
gets closer.

Pereira/Weiss

...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!6oXhXucCqMO6rFQZw4LhD3-riI-5FAbKI4WO1sf2hP8LT= oEz6p5IVVzBv2VrbH0G1tj2lmGYpsUo2RcvZ2Kbm3cNMKo$=20


$$

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FOUS11 KWBC 020730
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
230 AM EST Tue Dec 2 2025

Valid 12Z Tue Dec 02 2025 - 12Z Fri Dec 05 2025


...Mid-Atlantic & Northeast...=20
Days 1...

...Rapidly deepening coastal low will bring heavy snow to the
interior Mid-Atlantic and Northeast today/tonight...

Low pressure will move off the NC/VA coast this morning and then
track rapidly northeast along the coast, passing inside the 40N/70W
benchmark before lifting into the Canadian Maritimes by Wednesday
morning. The overlap of height falls, a coupled jet streak, and the
latent heat release along the offshore baroclinic gradient will
allow the low to rapidly deepen during this period, spreading
heavy precipitation and gusty winds into the Northeast.

As the low moves up the coast, persistent and impressive moist
isentropic ascent will surge a theta-e ridge northward to support
expanding heavy precipitation. The coincident WAA at 850mb will
produce additional ascent, with intensifying fgen driving some
banded precipitation, but also warm the column aloft as the surface
high pressure retreats rapidly to the east. The guidance has
trended just a bit warmer again overnight, and while most areas
along I-95 and points west will likely start as a brief period of
snow/sleet, any meaningful accumulation is anticipated only well
inland and at higher elevations, especially in southern and central
New England. The big cities from Washington, D.C. to Boston, MA may
start as snow before changing over to rain (and Boston may change
back to snow briefly before the system exits Wednesday morning).
However, well NW, WPC probabilities are high (>70%) for at least 6
inches of snow from the Catskills through the Berkshires, the
Worcester Hills, and across much of southern NH and ME (away from
the immediate coast) where locally as much as 12 inches is possible
(10-30% chance).

Additionally, while most of the freezing rain accompanying this
system is expected to wane before 12Z/Tuesday, an additional 0.1"
of ice is possible (10-30% chance) across the Central Appalachians
in the vicinity of Shenandoah NP.

Key Messages remain in effect for this system and are linked below
(Key Message #3)


...Northern to Southern Rockies...=20
Days 1-2...

A shortwave digging south out of British Columbia into the=20
northwestern U.S. will be positioned across the interior Northwest
to begin the forecast period /12z Tuesday/. This shortwave will=20
continue to move southeast through Wednesday, and may become more=20
amplified as it drops through the Great Basin in response to=20
secondary vorticity maxima digging through its base. This will=20
result in a slowing and amplification of the trough, with=20
downstream ascent maximizing through height falls, PVA, and=20
downstream intensifying jet energy, especially as it approaches the
Four Corners Wednesday morning.

Available moisture will generally be modest as reflected by near-
normal PW anomalies, but the overlapped synoptic lift will be more
than sufficient to wring this out as periods of moderate to heavy
snowfall across much of the terrain. At the same time, a wave of
low pressure is progged to drop southeast coincident with the
shortwave trough, and a secondary front will also push south out of
Canada to cool the column while additionally leading to localized
upslope flow. Despite a shallow DGZ noted in regional forecast
soundings, the best ascent is progged to intersect within this=20
snow growth region to enhance snowfall, and this suggests a broad=20
swath of moderate snow is likely today and Wednesday across much=20
of the Rockies.

WPC probabilities D1 for 6+ inches are highest in the terrain above
5000 ft from the Salmon River/Sawtooth Range of ID through the
Absarokas, Little Belts, Tetons, and down into the Park Range and
other CO Rockies. During D2, the highest probabilities shift south
with the shortwave and increase, reaching above 80% for 6+ inches
along much of the Sangre de Cristos where locally 12+ inches is
likely. Additionally, as this shortwave digs south, some moderate
snowfall is likely along the I-25 urban corridor of Colorado,
bringing some notable snow to a region that has yet to experience
much so far this winter.

...Great Lakes & Northeast...
Day 3...

A strong arctic front will race across the Great Lakes Wednesday,
likely reaching Upstate NY by Thursday morning before continuing
into New England and crossing offshore into the Atlantic Thursday
night. Environmental signals continue to appear favorable for snow
squalls along this front as it dives southeast, and the GFS and NAM
SnSQ parameter have both increased tonight, especially from western
PA through northern New England where a significant overlap of
0-2km fgen and SBCAPE as high as 200 J/kg exists in a region of
elevated low-level RH. This suggests increasing confidence in
linear snow squalls, especially Thursday. While snowfall=20
accumulations from this event will likely be minimal, brief intense
snow rates combined with gusty winds may create dangerous travel=20
across parts of the northern Great Lakes and interior Northeast.

Weiss


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!9CitJsY81sgfvgcKlG6ZrnnEIhWwB6pKIFXM58UDsWGWr= 9HKJE7T1O8YkkonalX1bNrkX6KvtEsUu9UtiQFpNXUEnak$=20



$$

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FOUS11 KWBC 022034
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
334 PM EST Tue Dec 2 2025

Valid 00Z Wed Dec 03 2025 - 00Z Sat Dec 06 2025


...Northeast...=20
Days 1...

Low pressure now moving north along the Mid Atlantic coast will
deepen rapidly through the evening as the associated shortwave
trough moves through the Northeast/Mid Atlantic, and assumes a
negative tilt as it moves offshore. This system will move quickly
overnight, tracking from near the 40N/70W benchmark at 00Z to east
of Nova Scotia by daybreak. The back edge of the associated=20
precipitation shield will move quickly to the east as well, with=20
snowfall ending for most areas apart from coastal northern New=20
England by tomorrow morning. Additional snowfall accumulations=20
after 00Z are expected to be light for most areas, with WPC=20
probabilities indicating the chance for accumulations greater than=20
4 inches are negligible for most areas, with some 10-30=20
probabilities confined to coastal Maine and southern New Hampshire.

...Northern to Southern Rockies...=20
Days 1-2...

A low amplitude shortwave trough dropping through the Pacific
Northwest today is forecast to amplify as it digs south along the=20
Sierra Nevada/Great Basin overnight, with the model consensus=20
showing a well-defined positively-tilted trough dropping into the=20 Southwest/Four Corners on Wednesday. Meanwhile at the surface, a cold
front will settle south into the southwestern U.S. A low level=20
circulation developing and dropping south through western Colorado=20
will help to enhance snowfall over the western Colorado ranges,=20
notably the San Juans, where WPC guidance shows some isolated=20
higher probabilities for accumulations greater than 6 inches on Day
1. More widespread higher amounts are expected to develop along=20
the eastern ranges from the Front Range south to the northern=20
Sangre de Cristos - supported by increasing upslope flow on the=20
backside of a sharp ridge nosing south along the High Plains.

=46rom Wednesday night into early Thursday, the shortwave over the
Southwest will begin to eject east, focusing snow further south
over the Rockies. Amounts are expected to me mostly light, with WPC probabilities indicating amounts over 6 inches will remain mostly
confined to the higher peaks of the southern Sangre de Cristos.


...Great Lakes & Northeast...
Days 1-3...

An arctic front associated with an amplifying trough over eastern=20
Canada will sweep across the upper Great Lakes on Wednesday,
setting off a period of lake effect snow showers that will continue
into early Thursday before a shortwave ridge moves over the region.
Overall, accumulations for the two-day period are expected to be=20
generally light. Although some parts of the eastern U.P. are likely
to see totals over 4 inches.

Meanwhile, the previously noted front will advance east of the
lakes, moving across the Northeast on Thursday. While heavy
accumulations along the front are not expected, snow squalls remain
a concern, with the NAM continuing to show some notable Snow=20
Squall Parameter values as the front advances across Upstate New=20
York and New England. This indicates a brief period of intense=20
snowfall that is likely to reduce visibilities and impact travel.=20
Behind the front, lake effect snow showers will develop briefly off
of lakes Erie and Ontario Wednesday night into Thursday, with the=20
best chance for heavy accumulations centered over the Tug Hill=20
region.

The aforementioned shortwave ridging is forecast to develop ahead
of another shortwave that is expected to dive southeast across
central Canada on Thursday and amplify as it brushes the upper=20
Great Lakes Friday morning. Most of the better forcing and lake
enhancement is expected to remain north of the lakes; however some
lighter amounts are likely, especially over northern Michigan.=20


...Mid South to the Mid Atlantic...
Day 3...

The previously noted shortwave over the Southwest will move east of
the southern Rockies on Thursday, becoming less amplified as it
moves into a region of confluent upper flow. However it will
provide enough lift to spread some light precipitation north into
the Mid South/Tennessee Valley, with a low end chance for some=20
light wintry precipitation/ice accumulations Thursday night into=20
early Friday. A greater chance for light snow/ice accumulations is=20
expected to develop farther east over the southern Appalachians,=20
where a cold air wedge is forecast to linger long enough to support
at least some minor accumulations on Friday.=20

Pereira

...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!5dX0zkdWbchHEQyfBkNAry9V7K3ebVmkRcD5w6GTZEdic= Rf4ygZ7kFSH-wJMsfxpoP2Zrn2TyshbLy4IoKDLGbL13OA$=20



$$

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FOUS11 KWBC 022051
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
351 PM EST Tue Dec 2 2025

Valid 00Z Wed Dec 03 2025 - 00Z Sat Dec 06 2025


...Northeast...=20
Days 1...

Low pressure now moving north along the Mid Atlantic coast will
deepen rapidly through the evening as the associated shortwave
trough moves through the Northeast/Mid Atlantic, and assumes a
negative tilt as it moves offshore. This system will move quickly
overnight, tracking from near the 40N/70W benchmark at 00Z to east
of Nova Scotia by daybreak. The back edge of the associated=20
precipitation shield will move quickly to the east as well, with=20
snowfall ending for most areas apart from coastal northern New=20
England by tomorrow morning. Additional snowfall accumulations=20
after 00Z are expected to be light for most areas, with WPC=20
probabilities indicating the chance for accumulations greater than=20
4 inches are negligible for most areas, with some 10-30=20
probabilities confined to coastal Maine and southern New Hampshire.

...Northern to Southern Rockies...=20
Days 1-2...

A low amplitude shortwave trough dropping through the Pacific
Northwest today is forecast to amplify as it digs south along the=20
Sierra Nevada/Great Basin overnight, with the model consensus=20
showing a well-defined positively-tilted trough dropping into the=20 Southwest/Four Corners on Wednesday. Meanwhile at the surface, a cold
front will settle south into the southwestern U.S. A low level=20
circulation developing and dropping south through western Colorado=20
will help to enhance snowfall over the western Colorado ranges,=20
notably the San Juans, where WPC guidance shows some isolated=20
higher probabilities for accumulations greater than 6 inches on Day
1. More widespread higher amounts are expected to develop along=20
the eastern ranges from the Front Range south to the northern=20
Sangre de Cristos - supported by increasing upslope flow on the=20
backside of a sharp ridge nosing south along the High Plains.

=46rom Wednesday night into early Thursday, the shortwave over the
Southwest will begin to eject east, focusing snow further south
over the Rockies. Amounts are expected to me mostly light, with WPC probabilities indicating amounts over 6 inches will remain mostly
confined to the higher peaks of the southern Sangre de Cristos.


...Great Lakes & Northeast...
Days 1-3...

An arctic front associated with an amplifying trough over eastern=20
Canada will sweep across the upper Great Lakes on Wednesday,
setting off a period of lake effect snow showers that will continue
into early Thursday before a shortwave ridge moves over the region.
Overall, accumulations for the two-day period are expected to be=20
generally light. Although some parts of the eastern U.P. are likely
to see totals over 4 inches.

Meanwhile, the previously noted front will advance east of the
lakes, moving across the Northeast on Thursday. While heavy
accumulations along the front are not expected, snow squalls remain
a concern, with the NAM continuing to show some notable Snow=20
Squall Parameter values as the front advances across Upstate New=20
York and New England. This indicates a brief period of intense=20
snowfall that is likely to reduce visibilities and impact travel.=20
Behind the front, lake effect snow showers will develop briefly off
of lakes Erie and Ontario Wednesday night into Thursday, with the=20
best chance for heavy accumulations centered over the Tug Hill=20
region.

The aforementioned shortwave ridging is forecast to develop ahead
of another shortwave that is expected to dive southeast across
central Canada on Thursday and amplify as it brushes the upper=20
Great Lakes Friday morning. Most of the better forcing and lake
enhancement is expected to remain north of the lakes; however some
lighter amounts are likely, especially over northern Michigan.=20


...Mid South to the Mid Atlantic...
Day 3...

The previously noted shortwave over the Southwest will move east of
the southern Rockies on Thursday, becoming less amplified as it
moves into a region of confluent upper flow. However it will
provide enough lift to spread some light precipitation north into
the Mid South/Tennessee Valley, with a low end chance for some=20
light wintry precipitation/ice accumulations Thursday night into=20
early Friday. A greater chance for light snow/ice accumulations is=20
expected to develop farther east over the southern Appalachians,=20
where a cold air wedge is forecast to linger long enough to support
at least some minor accumulations on Friday.=20

...Northern Rockies...
Day 3...

The next chance for heavy snowfall totals in the northern Rockies
will develop as a low amplitude shortwave slides off of the top of
the Pacific ridge into the region late Thursday into Friday.=20
Favorable mid to upper level forcing along with a notable influx of
Pacific moisture will be sufficient for some heavy totals over the
northern Rockies from northern Idaho and western Montana to=20
western Wyoming -- where WPC probabilities indicate widespread=20
totals over 4 inches are likely, with amounts over 8 inches=20
possible in the higher terrain.=20

Pereira

...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!_o-SUQXPmGVKCQUA40WQkjG6mxm--y--ExzoWHd0zGwiZ= t3WKbKCcaAGBk-7uBOjIe-o6HDQyb7eerxWCf07fenphZ0$=20



$$

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FOUS11 KWBC 030755
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
255 AM EST Wed Dec 3 2025

Valid 12Z Wed Dec 03 2025 - 12Z Sat Dec 06 2025


...Southern/Central Rockies...
Days 1-2...

Shortwave which emerged from British Columbia Monday will continue
to track southeast across the Four Corners today while amplifying.
The guidance has trended a bit farther south and more amplified
with the evolution today, which should result in heavier snowfall
especially across the San Juans and Sangre de Cristos on D1.
Forcing for ascent downstream of this trough (in response to height
falls and modest divergence) will be enhanced by a strengthening
jet streak, especially tonight into Thursday morning, and periods
of impressive upslope flow as cold N/NE winds develop in advance of
an Canadian high pressure dropping into the Plains. Moisture within
the region is progged to be around to slightly below normal as
reflected by NAEFS ensembles, but the impressive overlapping ascent
will still maximize favorable to support heavy snow, especially
above 4000-5000 ft, with snow levels falling in conjunction with
waning snowfall intensity. WPC probabilities, especially across the
San Juans and Sangre de Cristos, have increased tonight, and now
feature a high risk (>70%) for more than 12 inches in the higher
terrain of these ranges. Into the lower terrain, WPC probabilities
indicate a moderate threat (30-50%) for at least 4" along the I-25
urban corridor, with locally more than 6" in the higher terrain of
the Raton Mesa and southern Palmer Divide.


...Great Lakes & Northeast...
Days 1-3...

Progressive flow across the Northeast will manifest in response to
a large gyre centered near Hudson Bay, which will shed periodic
shortwaves from the Great Lakes through the Northeast leading to
occasional enhanced ascent and lowered heights throughout. In
response to this evolution, the period will remain active through
LES and arctic fronts, and multiple rounds of snowfall, sometimes
heavy, are expected.

The first event will be associated with an arctic cold front
dragging southeast beneath a shortwave aloft. This front will
likely move rapidly across the Great Lakes today, and then across
the Northeast Thursday. Along and ahead of this front, the
environment continues to suggest an increasing threat for snow
squalls, especially across PA/NY and New England on Thursday. The
NAM SnSq parameter continues to be more aggressive than the GFS,
but the antecedent low-level environment ahead of the front appears
favorable for squall development. With 0-2km fgen maximizing along
the front into elevated RH and SBCAPE as high as 300 J/kg,
widespread linear squalls could result. Upstream into MI the threat
is not as high on D1, and although isolated squalls could occur,
the greater risk will be D2 in the Northeast. While total snowfall
will be minimal in any squall, rapidly changing conditions due to
heavy snow and gusty winds will create periods of dangerous travel
Thursday aftn. These squalls could become widespread, and after
coordination with the northeast WFOs, it is possible that with
future model cycles some enhanced messaging may be needed to
highlight the threat.

Behind this front, as well as behind a subsequent shortwave on
Friday, increased CAA will spread across the Great Lakes leading to
periods of lake effect snow (LES). The progressive flow will
support shortwave ridging between the two impulses, so the duration
of any LES with each shortwave/front should be somewhat limited.
However, 850mb temps falling to -15C to -20C Wednesday
night/Thursday, and then -10C to -15C late Friday, will create
steep lapse rates and deepening inversion depths to support bands
of heavy LES. The heaviest LES snowfall accumulations within the
LES bands are expected in the typical NW snow belts across the U.P.
of MI, the NW L.P. near Traverse City, and then along the
Chautauqua Ridge and into the Tug Hill Plateau. In these belts,
3-day snowfall of 6-12 inches is possible, highest across the U.P.


...Mid-South to the Mid-Atlantic...
Day 3...

Uncertainty abounds D3 with respect to a strung-out shortwave
exiting the Central Plains and becoming embedded within the more
zonal flow to the east. Although this shortwave is expected to be
of modest amplitude and fast moving, the accompanying upper jet is
progged to be powerful at over 150kts across the Mid-Atlantic,
leading to surface low pressure development across the Southeast.
This low will then race E/NE, producing a swath of at least light
wintry precipitation from the Tennessee Valley to the Mid-Atlantic
states.

There has been at least a modest northward shift/trend in the MSLP
fields from the various global ensembles the past few runs, and
while the ECMWF operational remains the most aggressive/north, that
solution cannot be ruled out. In fact, the trends in the 250mb jet
streak and from evaluation of the clusters (for which the primary
variance is the amplitude of the trough across the east) could
suggest a more subtle northward track of this low which would shift
more wintry precipitation into the area. It is still too early to
iron out these details, but at least a low-end risk for a few
inches of snow is possible as reflected by WPC probabilities which
reach 10-30% for 1+ inches of snow across the Central Appalachians
and into eastern VA/MD. This is notably lower than the recent NBM probabilities, and the trends continue to increase, so it is worth
watching the evolution of this event during the next few days.

South of the potential moderate snow, an axis of light freezing
rain is also possible where a p-type transition occurs. While the
location of the heaviest icing is also uncertain, current WPC
probabilities indicate a 10-30% chance for at least 0.1" of ice
across northern NC and into southern VA.


...Northern to Central Rockies...
Days 2-3...

The next chance for heavy snowfall totals in the northern Rockies
will develop as a low amplitude shortwave slides off of the top of
the Pacific ridge into the region late Thursday into Friday,
coincident with the LFQ of an impressive upper jet streak swinging
across the Northern Pacific. This will result in favorable mid to
upper level forcing along with a notable influx of Pacific
moisture, sufficient for some heavy totals , especially above
around 5000 ft as snow levels rise coincident with this moisture
plume moving into the area. Heavy snowfall accumulations are likely
D2 from the WA Cascades through the terrain of NW WY near
Yellowstone NP as reflected by WPC probabilities that suggest a
high risk (>70%) for 4+ inches, with impacts to many of the area
passes becoming likely.

Probabilities become even more impressive D3 across the higher
terrain from Glacier NP through Yellowstone NP including portions
of the Sawtooth/Salmon River ranges, Absarokas, terrain of NW WY,
and into the Park Range of CO. Here, WPC probabilities D3 reach
above 70% for 8+ inches, and D3 snowfall could be impressive above
generally 6000 ft where locally 1-2 feet is possible.

Weiss



$$

= = =
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FOUS11 KWBC 032015
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
315 PM EST Wed Dec 3 2025

Valid 00Z Thu Dec 04 2025 - 00Z Sun Dec 07 2025


...Southern/Central Rockies...=20
Day 1...

The sharp, positively-titled trough currently over the Four=20
Corners states will continue to translate eastward tonight before=20
ejecting into the central/southern Plains on Thursday. Forcing for=20
ascent downstream of this trough (in response to height falls and=20
modest divergence) will be enhanced by a strengthening jet streak,=20 especially tonight into Thursday morning. Meanwhile, Canadian high=20
pressure dropping into the Plains will result in impressive upslope
flow as cold N/NE winds develop in response. Moisture within the=20
region is progged to be around to slightly below normal as=20
reflected by NAEFS ensembles, but the impressive overlapping ascent
will still be favorable to support heavy snow. This will=20
especially be the case above 4000-5000 ft, with snow levels falling
in conjunction with waning snowfall intensity later tonight into=20
Thursday morning. The latest WPC probabilities continue to show=20
moderate to high chances (40-80%) for additional accumulations of=20

6 inches across portions of the southern San Juans and Sangre de=20

Cristo mountain ranges, with low to moderate chances (20-50%) of >8
inches.


...Great Lakes & Northeast...
Days 1-3...

Progressive flow across the Northeast will manifest in response to
a large gyre centered near Hudson Bay, which will shed periodic=20
shortwaves from the Great Lakes through the Northeast leading to=20
occasional enhanced ascent and lowered heights throughout. In=20
response to this evolution, multiple rounds of snowfall, sometimes=20
heavy, are expected through the period.=20

The first event will be associated with an arctic cold front=20
dragging southeast beneath a shortwave aloft. This front will move=20
rapidly across the eastern Great Lakes tonight, and then across the
Northeast on Thursday. Along and ahead of this front, the=20
environment continues to suggest an increasing threat for snow=20
squalls, especially across Upstate NY and New England on Thursday.=20
With 0-2km fgen maximizing along the front into elevated RH and=20
SBCAPE as high as 300 J/kg, widespread linear squalls are likely.=20
While total snowfall will be minimal in any squall, rapidly=20
changing conditions due to heavy snow and gusty winds will create=20
periods of dangerous travel Thursday afternoon and evening. As a=20
result, WPC has initiated Key Messages to highlight this event. See
the link below for more details.

Behind this front, as well as behind a subsequent shortwave on=20
Friday, increased CAA will spread across the Great Lakes leading to
periods of lake effect snow (LES). The progressive flow will=20
support shortwave ridging between the two impulses, so the duration
of any LES with each shortwave/front should be somewhat limited.=20
However, 850mb temps falling to between -15C to -20C Thursday, and=20
then between -10C to -15C late Friday into Saturday, will create=20
steep lapse rates and deepening inversion depths to support bands=20
of heavy LES. The heaviest LES snowfall accumulations within the=20
LES bands are expected in the typical NW snow belts across the U.P.
of MI, the NW L.P. near Traverse City, and then along the=20
Chautauqua Ridge and into the Tug Hill Plateau. In these belts,=20
3-day snowfall of 6-12 inches is possible, highest across the U.P.


...Mid-South to the Mid-Atlantic...=20
Day 2...

Plenty of uncertainty heading into Day 2 with respect to a strung-
out shortwave exiting the Central Plains and becoming embedded=20
within the more zonal flow to the east. Although this shortwave is=20
expected to be of modest amplitude and fast moving, the=20
accompanying upper jet is progged to be powerful at over 150kts=20
across the Mid-Atlantic, leading to surface low pressure=20
development across the Southeast. This low will then race E/NE,=20
producing a swath of at least light wintry precipitation from the=20
Tennessee Valley to the Mid-Atlantic states.=20

There has been at least a modest northward shift/trend in the=20
MSLP/QPF fields from the various global ensembles the past few=20
runs, with the ECMWF and various machine learning suites the=20
farthest north. While it still remains too early to iron out the=20
details, WPC probabilities of 1+ inches of snow across the Central=20 Appalachians and into eastern VA/MD have increased to 20-60%, with=20
the highest chances in the higher terrain of WV/VA. WPC=20
probabilities for 2+ inches are between 10-20% from eastern WV to=20
central VA.

South of the potential moderate snow, an axis of light
freezing rain is also possible where a p-type transition occurs
underneath a stubborn layer of low-level cold air. The latest WPC=20 probabilities maintain a 10-30% chance for at least 0.1" of ice=20
across northern NC and into southern VA.


...Northern to Central Rockies...=20
Days 1-3...

The next chance for heavy snowfall totals in the northern Rockies=20
will develop as a low amplitude shortwave slides off of the top of=20
the Pacific ridge into the region late Thursday into Friday,=20
coincident with the LFQ of an impressive upper jet streak swinging=20
across the Northern Pacific. This will result in favorable mid to=20
upper level forcing along with a notable influx of Pacific=20
moisture, sufficient for some heavy totals, especially above around
5000 ft as snow levels rise coincident with this moisture plume=20
moving into the area. Heavy snowfall accumulations are likely from=20
the WA Cascades through the terrain of NW WY near Yellowstone NP as
reflected by WPC probabilities that suggest a high risk (>70%) for
4+ inches, with impacts to many of the area passes becoming=20
likely.

Probabilities become even more impressive Day 2 and 3 across the=20
higher terrain from Glacier NP through Yellowstone NP including=20
portions of the Sawtooth/Salmon River ranges, Absarokas, terrain of
NW WY, northern Utah, and into the Park Range of CO. Here, WPC=20
probabilities Day 2 and 3 reach above 70% for 8+ inches, and Day 2=20
and Day 3 snowfall could be impressive above generally 6000 ft=20
where locally 1-2 feet is possible.

Miller/Weiss




...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!4ONBRMdITod6KQZeFxmplUpEcL6FhhdNmsyM3cstn2js_= 1Nv2iBrrRRCa5z0OsCbPZ1yd7WcRTVv4VpGUAMNxmUzroo$=20



$$

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