ACUS48 KWNS 050900
SWOD48
SPC AC 050859

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0259 AM CST Thu Dec 05 2024

Valid 081200Z - 131200Z

...DISCUSSION...
Ridging will start to build into the Southeast this weekend with a
series of troughs moving through the western CONUS as a more
progressive pattern evolves. As ridging builds across the Southeast,
the surface pattern will result in favorable trajectories for
significant moisture recovery across the Gulf of Mexico. Some of
this richer moisture will likely advect inland across portions of
the Gulf Coast and Southeast early next week. The inland moisture
intrusion combined with the arrival of several troughs within a
progressive pattern would suggest the potential for some severe
weather. However, there still remains uncertainty in the upper-level
pattern and the degree of destabilization.

The ECMWF shows a sharpening trough moving across east Texas late
Sunday. A strengthening low-level jet will be associated with this
trough with increasing low-level moisture across parts of East Texas
and Louisiana. However, instability is forecast to remain quite weak
with a mostly moist-adiabatic thermodynamic environment in the
region. Some severe weather could be possible in this scenario, but
the weak instability will likely preclude a greater threat. The GFS
shows more of a closed low moving into the central Plains with
forcing further displaced from the better low-level moisture and
thus minimal severe weather potential on Day4/Sunday.

Beyond Day 4 there will be some severe weather potential as a large
trough crosses the western CONUS and digs into the southern Plains
with moisture inland across the Gulf Coast and Southeast. A wide
range of possibilities remain due to the complicated upper-level
pattern and variance among forecast guidance. Therefore, there are
no specific periods with greater severe weather concern, but the
extended range will need to be monitored given the presence of an
approaching large-scale trough and inland 60F+ dewpoints.

..Bentley.. 12/05/2024

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ACUS48 KWNS 060937
SWOD48
SPC AC 060936

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0336 AM CST Fri Dec 06 2024

Valid 091200Z - 141200Z

...DISCUSSION...
Medium-range guidance is in relatively good agreement that
significant amplification of the upper pattern will take place next
week as a strong and deep upper trough traverses the CONUS. The
initial development of this upper trough is forecast to begin on
D4/Monday as a shortwave trough moves through the Great Basin into
the Southwest while another moves from the Upper Midwest across the
Upper Great Lakes and Ontario. By early D5/Tuesday, evolution of
these systems will have likely resulted in broad and deep upper
troughing across much of the central North America. This trough is
then expected to continue eastward as a shortwave trough progresses
through its base, helping to sharpen the trough and strengthening
mid-level flow. Consensus within the guidance places a 120 kt 500 mb
jet streak from AL through the central Appalachians on D6/Wednesday.
The embedded shortwave is forecast to continue quickly
eastward/northeastward across the Southeast and Mid-Atlantic on
D6/Wednesday, helping to induce a more negative tilt to the parent
upper troughing.

A strong cold front will likely accompany this system, progressing
eastward through the Plains on D4/Monday, the MS and OH Valleys and
Southeast on D5/Tuesday, and off the East Coast on D6/Wednesday.
Favorable low-level moisture may be in place ahead of this front
across the Southeast on D5/Tuesday. However, a front-parallel
orientation of the deep-layer shear is anticipated, and buoyancy
will likely remain modest, limiting severe potential. Favorable
low-level moisture may exist ahead of the front across the
Mid-Atlantic on D6/Wednesday as well, with strengthening deep-layer
vertical shear and large-scale ascent anticipated across the region
as well. As a result, some severe appears possible, but uncertainty
regarding frontal position limits predictability.

..Mosier.. 12/06/2024

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ACUS48 KWNS 070953
SWOD48
SPC AC 070951

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0351 AM CST Sat Dec 07 2024

Valid 101200Z - 151200Z

...DISCUSSION...
Extensive upper troughing is expected to cover much of central North
America early D4/Tuesday. This trough is then expected to continue
eastward as a shortwave trough progresses through its base, helping
to sharpen the trough and strengthening mid-level flow. Consensus
within the guidance places a 100-120 kt 500 mb jet streak from AL
through the central Appalachians on D5/Wednesday. The embedded
shortwave is forecast to continue quickly eastward/northeastward
across the Southeast and Mid-Atlantic on D5/Wednesday, helping to
induce a more negative tilt to the parent upper troughing.

A strong cold front will likely accompany this system, progressing
eastward through the MS and OH Valleys and Southeast on D4/Tuesday,
and off the East Coast on D5/Wednesday. Favorable low-level moisture
may be in place ahead of this front across the Southeast on
D4/Tuesday. However, a front-parallel orientation of the deep-layer
shear is anticipated, and buoyancy will likely remain modest,
limiting severe potential. Favorable low-level moisture may exist
ahead of the front across the Mid-Atlantic on D5/Wednesday as well.
However, poor lapse rates should keep buoyancy low and the current
expectation is that updrafts will struggle to maintain depth,
limiting the severe potential.

Consensus within the guidance is for the pattern to trend less
amplified in the wake of the strong mid-week upper trough from
D6/Thursday through D8/Saturday, with several shortwave troughs
likely traversing the more zonal flow. Guidance varies on the
location, strength, and speed of these shortwaves, but the impact of
these waves will likely be mitigated by predominantly stable surface
conditions on D6/Thursday and D7/Friday. Some moisture return may
begin on D7/Friday across the southern Plains, continuing into
D8/Saturday, but guidance currently suggests that buoyancy will
remain limited.

..Mosier.. 12/07/2024

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ACUS48 KWNS 081001
SWOD48
SPC AC 081000

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0400 AM CST Sun Dec 08 2024

Valid 111200Z - 161200Z

...DISCUSSION...
Medium-range guidance is in good agreement that a deep upper trough
will be over much of the central and eastern CONUS early
D4/Wednesday morning. At the same time, a surface low is forecast to
be over eastern PA, with an attendant cold front extending
southwestward from this low across the central Carolinas,
southeastern GA, and northern FL.

A shortwave trough is forecast to move within the larger upper
troughing, moving from the TN Valley/Southeast through the
Mid-Atlantic on D4/Wednesday. This evolution will help induce a more
negative tilt to the parent troughing while encouraging an eastward
shift and deamplification as well. The cold front will also quickly
shift eastward off the East Coast. A fairly narrow warm sector may
precede this front, but poor lapse rates will limit instability.
This low buoyancy will counter the strong shear expected, resulting
in mostly weak updrafts and tempering any severe potential.

Stable conditions are expected across the CONUS on D5/Thursday as
high pressure shifts from the northern Plains into the OH Valley.
Some modest moisture return may potentially begin across TX on
D6/Friday ahead of a low-amplitude, southern-stream shortwave trough
expected to move across the southern Plains late D6/Friday and early D7/Saturday. Guidance varies on the strength and speed of this wave,
limiting predictability, but some thunderstorms are possible across central/east TX and LA late D6/Friday and early D7/Saturday as this
wave interacts with the return moisture.

..Mosier.. 12/08/2024

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ACUS48 KWNS 090930
SWOD48
SPC AC 090928

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0328 AM CST Mon Dec 09 2024

Valid 121200Z - 171200Z

...DISCUSSION...
Cyclonic upper flow and stable low-level conditions are expected
across the central and eastern CONUS on D4/Thursday as surface high
pressure shifts from the northern Plains into the OH Valley. At the
same time, a low-amplitude, southern-stream shortwave trough is
forecast to progress across the Great Basin and Four Corners before
then continuing into the central/southern Plains on D5/Friday and
Mid MS Valley on D6/Saturday.

Surface cyclogenesis will likely precede this shortwave over the
central Plains on D5/Friday, with low-level moisture advection
anticipated over the southern Plains as well. The quality of this
moisture advection will be tempered by the strength of a preceding
cold front, with mid 60s dewpoints likely remaining confined to the
TX Gulf Coast. Even so, thunderstorms still appear possible late
Friday into early Saturday along and ahead of the cold front from
east TX into the Ozarks, and across the Lower MS Valley on
D6/Saturday. Uncertainty regarding the quality of the moisture
return (and related buoyancy) as well as general uncertainties
regarding the strength and timing of the shortwave limit overall
predictability of the severe thunderstorm potential.

..Mosier.. 12/09/2024

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ACUS48 KWNS 100958
SWOD48
SPC AC 100957

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0357 AM CST Tue Dec 10 2024

Valid 131200Z - 181200Z

...DISCUSSION...
Medium-range guidance is in good agreement that a shortwave trough
will move from the central Rockies through the central Plains on
D4/Friday. An associated surface low will take a similar track just
ahead of the parent wave, with an attendant cold front pushing
eastward across the southern/central Plains. Some modest moisture
return will precede this front, and thunderstorms appear possible
from east TX into the Lower MO Valley D4/Friday night into
D5/Saturday morning. A few strong storms are possible, but overall
buoyancy will likely remain modest due to warm mid-level
temperatures, and the highest dewpoints are expected to remain
displaced south of the better forcing.

This shortwave and attendant cold front will likely continue
eastward on into the MS Valley on D5/Saturday and through the
remainder of the eastern CONUS on D6/Sunday. Thunderstorms are
possible over portions of the Lower MS Valley and Mid-South on
D5/Saturday and the Carolinas on D6/Sunday. Limited buoyancy should
keep any severe-weather threat isolated.

Another shortwave trough is expected to move across CA and the Great
Basin on D6/Sunday and through the central Plains and Mid MS Valley
on D7/Monday. Similar to the earlier shortwave, the strongest
forcing for ascent with this shortwave is expected to remain
displaced north of the better low-level moisture and buoyancy,
likely tempering the overall severe potential. Even so,
thunderstorms are possible, and greater moisture return (and
buoyancy) is possible if the preceding cold front remains weak over
the southern Plains.

..Mosier.. 12/10/2024

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ACUS48 KWNS 110950
SWOD48
SPC AC 110948

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0348 AM CST Wed Dec 11 2024

Valid 141200Z - 191200Z

...DISCUSSION...
A progressive upper pattern is expected in the extended, with
several low-amplitude shortwave troughs forecast to traverse the
CONUS. Lead shortwave in this series will likely be over the central
Plains on D4/Saturday morning before then moving through the Mid MS
Valley by late D4/Saturday and through the OH Valley on D5/Sunday.
Another shortwave is expected to follow in the wake of the first,
progressing across the Great Basin and Four Corners on D5/Sunday and
the southern/central Plains on D6/Monday. This wave may phase with
another shortwave moving through central Canada, with resultant
troughing extended from the Canadian Prairies into the southern
Plains by D6/Monday afternoon. Yet another shortwave is currently
progged to drop from the Pacific Northwest/northern CA into the
Great Basin late D6/Monday. Guidance varies significantly on the
evolution of this wave, and its strength/maturity and location
currently have limited predictability.

Moisture return is anticipated across the Plains ahead of each of
these waves. Enough moisture and buoyancy should exist ahead of the
first shortwave to support thunderstorms, as it moves eastward on
into the MS Valley on D4/Saturday and through the remainder of the
eastern CONUS on D5/Sunday.

The most significant moisture return is currently expected ahead of
the second shortwave on D5/Sunday and D6/Monday. Thunderstorms are
likely as the shortwave and associated cold front interact with this
return moisture, although variability within the guidance of the
strength and speed of this wave results in differing areas of
highest thunderstorm coverage. Some severe appears possible,
particularly if the wave is stronger and further south as suggested
by the 00Z ECMWF.

..Mosier.. 12/11/2024

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ACUS48 KWNS 120921
SWOD48
SPC AC 120920

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0320 AM CST Thu Dec 12 2024

Valid 151200Z - 201200Z

...DISCUSSION...
Most of the medium-range guidance has trend faster and less
amplified with the shortwave trough expected to move from the Four
Corners region through the central Plains on D4/Sunday. This more
northerly progression will limit the interaction between this wave
and any returning low-level moisture, which should limit
thunderstorm potential throughout most of the day.

Another shortwave trough is expected to follow in the wake of this
lead wave, but with a more southerly track across the Southwest and
into the southern Plains. Guidance is in relatively good agreement
that this wave will move over the southern High Plains late
D4/Sunday into early D5/Monday. This wave is expected to interact
with the returning low-level moisture, with thunderstorm development
along and ahead of its associated front from central OK/north TX
into the Ozarks early Monday morning. Thunderstorms are expected to
gradually shift eastward throughout the day D5/Monday, expanding
into more of east/southeast TX and the Mid/Lower MS Valley.
Seasonally warm and moist conditions are anticipated, and enough
buoyancy and shear could be in place for severe thunderstorms.
However, overall buoyancy will likely be mitigated by poor lapse
rates, and warm mid-level temperatures could contribute to some
inhibition. There is also some potential for a more front-parallel
orientation, which could result in a more anafrontal character to
the storms. These factors, combined with the notable variability
within the guidance, introduce enough uncertainty to merit
withholding any severe probabilities for D4/Sunday or D5/Monday with
this outlook.

Another shortwave trough may progress into the Plains on
D7/Wednesday, with preceding moisture return across the southern
Plains setting up the potential for thunderstorms as this wave and
its associated cold front push eastward/southeastward across the
southern Plains. However, GEFS members show large differences on how
this wave progresses, with notable differences within the ECMWF
members too. Some members within both of these ensemble systems
suggest the development of a closed low over the Southwest instead
of progressive wave into the Plains. Consequently, as with the
earlier wave, predictability issues limit forecast confidence.

..Mosier.. 12/12/2024

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ACUS48 KWNS 130939
SWOD48
SPC AC 130937

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0337 AM CST Fri Dec 13 2024

Valid 161200Z - 211200Z

...DISCUSSION...
A shortwave upper trough will traverse the Midwest and Great Lakes
region on Day 4/Mon. Meanwhile, a cold front will track southeast
across the southern Plains and Mid-South vicinity, extending from
northern AL toward the Upper TX Coast/south-central TX by early Day
5/Tue. Southerly low-level flow ahead of the front will bring Gulf
moisture across the south and east Texas into the lower MS
Valley/central Gulf coast region, aiding in modest destabilization
on Monday. However, stronger mid/upper level flow and large-scale
ascent will remain north over the Midwest. Furthermore, deep-layer
flow will mostly be parallel to the cold front. As a result,
warm-advection precipitation and thunderstorms are likely from east
TX into the Lower MS Valley, but severe potential appears limited.

The cold front from Day 4/Mon will likely stall on Day 5/Tue across
parts of the TX coast and Lower MS Valley. By late Tuesday into Day
6/Wed, another upper trough is expected to eject across the Plains
into the Southeast. A sharper cold front associated with this system
will move offshore the Gulf coast, with some potential for heavy
rain and thunderstorms. However, given prior days' convection, poor heating/widespread cloudiness and weak instability, severe potential
is not expected. Given the strong cold front intruding into the
Gulf, boundary-layer moisture will become scant and severe-
thunderstorm potential is expected to be low Days 7-8/Thu-Fri.

..Leitman.. 12/13/2024

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ACUS48 KWNS 140828
SWOD48
SPC AC 140827

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0227 AM CST Sat Dec 14 2024

Valid 171200Z - 221200Z

...DISCUSSION...
An upper trough over the High Plains vicinity Day 4/Tue morning will
deepen and track east to the MS Valley by Day 5/Wed, and to the
Atlantic coast by Day 6/Thu. As this occurs, a cold front will move
across the south-central and southeast states, pushing offshore the
Gulf and Atlantic coasts by late Day 5/Wed into early Day 6/Thu.
While thunderstorm potential will be possible with this system,
severe potential appears limited, given weak instability and
deep-layer flow oriented parallel to the surface boundary (leading
to more anafrontal processes).

With the strong front moving well into the Gulf of Mexico,
boundary-layer moisture will remain scant heading into the end of
the forecast period, and severe-thunderstorm potential is expected
to remain low Days 7-8/Fri-Sat.

..Leitman.. 12/14/2024

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ACUS48 KWNS 150913
SWOD48
SPC AC 150912

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0312 AM CST Sun Dec 15 2024

Valid 181200Z - 231200Z

...DISCUSSION...
A surface cold front will move south and east across the eastern and southeastern U.S. on Day 4/Wed, moving offshore the Gulf and
Atlantic coasts by early Day 5/Thu. Showers and thunderstorms are
possible near the cold front across parts of the Southeast and
Mid-Atlantic vicinity on Day 4/Wed. However, weak instability and
only modest vertical shear is expected to limit severe thunderstorm
potential.

After Day 4/Wed, a mean upper level trough will persist over the
eastern half of the CONUS, while an amplified upper ridge develops
over the West. As the early period cold front continues to intrude
southward across the Gulf of Mexico, boundary-layer moisture will
become scant across the CONUS, and offshore trajectories will
persist through the period. This overall pattern will result in
limited thunderstorm potential beyond Day 4/Wed, and severe storms
are not expected.

..Leitman.. 12/15/2024

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ACUS48 KWNS 160948
SWOD48
SPC AC 160947

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0347 AM CST Mon Dec 16 2024

Valid 191200Z - 241200Z

...DISCUSSION...
Medium range guidance is in fairly good agreement that an amplified
but progressive upper level pattern will overspread the CONUS during
the Day 4-8 period. A shortwave trough over the northern Plains
early on Day 4/Thu will deepen and spread east over the eastern half
of the CONUS through Day 6 or 7/Sat or Sun. Meanwhile, an amplified
upper ridge will build over the western states and spread east into
the Plains during this same time period. Spread among guidance
increases around Day 6-8/Sat-Mon, but still indicates that another
upper trough will emerge over the Plains and Midwest late in the
period.

A surface cold front will move south and east into the Gulf of
Mexico and offshore the Atlantic coast on Thursday. This will clear
out any lingering boundary-layer moisture and persistent offshore
trajectories will mostly preclude much thunderstorm potential for
most of the forecast period. The exception may be on Day 7-8/Sun-Mon
as lee troughing allow for southeasterly flow to return across the
western Gulf and TX, bringing modest moisture northward across
southern/central TX. Nevertheless, severe-thunderstorm potential
appears low throughout the forecast period.

..Leitman.. 12/16/2024

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ACUS48 KWNS 170934
SWOD48
SPC AC 170933

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0333 AM CST Tue Dec 17 2024

Valid 201200Z - 251200Z

...DISCUSSION...
Strong surface high pressure over the central U.S. and a prior cold
front intruding into the southern Gulf of Mexico will result in a
dearth of boundary layer moisture across much of the CONUS through
at least Day 6/Sun. As a result, thunderstorm chances will be low.
Toward the end of the period, some forecast guidance suggests lee
troughing will allow southeasterly low-level flow to bring modest
Gulf moisture northward across TX. This may result in some increased thunderstorm chances across south/central TX on Day 7-8/Mon-Tue.
However, severe-thunderstorm potential will remain low during the
Day 4-8 time frame.

..Leitman.. 12/17/2024

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ACUS48 KWNS 180940
SWOD48
SPC AC 180939

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0339 AM CST Wed Dec 18 2024

Valid 211200Z - 261200Z

...DISCUSSION...
Strong surface high pressure and a dearth of boundary-layer moisture
will preclude severe thunderstorm potential on Days 4-5/Sat-Sun.

By Day 6/Mon, medium range forecast guidance shows a series of upper
shortwave troughs shifting east from the Rockies to the MS Valley
through Day 8/Wed (Christmas Day). In response, lee
troughing/surface low developing is expected over parts of the
southern Plains. Increasing southerly low-level flow will support
modest northward transport of Gulf moisture across parts of TX into
OK, and eventually the Lower MS Valley near the end of the period.
While there is still quite a bit of spread with regards to
intensity, location, and timing of these features, increasing
thunderstorm activity is expected Day 6-8/Mon-Wed across the
southern Plains vicinity. While uncertainty is high, if timing and
overlap of key features comes to fruition, some severe risk could be
possible over the upcoming Christmas holiday period.

..Leitman.. 12/18/2024

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ACUS48 KWNS 190846
SWOD48
SPC AC 190845

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0245 AM CST Thu Dec 19 2024

Valid 221200Z - 271200Z

...DISCUSSION...
Strong surface high pressure and a dearth of boundary-layer moisture
will limit thunderstorm potential on Day 4/Sun. Starting Day 5/Mon,
a progressive upper level pattern is forecast, and a series of
shortwave trough will migrate across the Plains to the Midwest. As
this occurs, surface lee troughing will support south/southeasterly
low-level flow across the southern Plains and the Gulf of Mexico.
Modest boundary-layer moisture will being to return northward across
TX toward OK by early next week, and eventually into the Lower MS
Valley by mid to late in the week. Large spread remains regarding
the timing and intensity of these features across the south-central
U.S. However, thunderstorm potential will begin increasing starting
Day 5/Monday across OK/TX, shifting east with time through Day
8/Thu. Some severe-thunderstorm potential could accompany this
activity, but predictability is too low at this time to include
outlook delineations at this time.

..Leitman.. 12/19/2024

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ACUS48 KWNS 200905
SWOD48
SPC AC 200904

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0304 AM CST Fri Dec 20 2024

Valid 231200Z - 281200Z

...DISCUSSION...
A more active southern-stream pattern should evolve next week, with
several lower latitude troughs crossing the southern tier along with
some northward increase in low-level moisture across parts of Texas
to the Lower Mississippi Valley and Gulf Coast. One such shortwave
trough should influence increasing thunderstorm potential across
east/southeast Texas on Tuesday/Day 5. Some severe risk could
materialize, but it appears that overall buoyancy will be weak with
the severe potential currently expected to be relatively marginal
and isolated in nature.

An additional focus for increasing deep convective potential will be
into the Thursday/Day 7 and Friday/Day 8 time frame. This will be as
a secondary upper trough emerges from the Southwest deserts. This
could lead to some severe risk in a corridor from east/southeast
Texas and ArkLaTex to Lower Mississippi Valley. However, there is
some uncertainty regarding moisture/destabilization given the
potential influences of the preceding shortwave trough and cold
front. Forecast uncertainties at this time frame precludes any 15%
outlook areas.

..Guyer.. 12/20/2024

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ACUS48 KWNS 210923
SWOD48
SPC AC 210922

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0322 AM CST Sat Dec 21 2024

Valid 241200Z - 291200Z

...DISCUSSION...
A more active southern-stream pattern is expected next week with
several lower latitude troughs crossing the southern tier, along
with some northward increase in low-level moisture across parts of
Texas to the Lower Mississippi Valley and Gulf Coast. On Tuesday/Day
4, one such shortwave trough should influence increasing
thunderstorm potential across south-central to east/southeast Texas.
Some severe risk could materialize Tuesday, but it appears that
overall buoyancy will be weak with the severe potential currently
expected to be relatively marginal and isolated in nature.

An additional focus for increasing deep convective potential will be
into the Thursday/Day 6, Friday/Day 7, and Saturday/Day 8 time
frame. This will be as a secondary upper trough emerges from the
Southwest deserts and moves toward the Deep South. This could lead
to a severe risk in a corridor from east/southeast Texas and the
ArkLaTex to Lower Mississippi Valley. While some severe storms will
be possible, perhaps especially Thursday/Day 6, there is lingering
risk magnitude uncertainty related to moisture/destabilization given
the potential influences of the preceding shortwave trough and cold
front. Forecast uncertainties at this time frame precludes any 15%
outlook areas.

..Guyer.. 12/21/2024

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ACUS48 KWNS 221002
SWOD48
SPC AC 221000

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0400 AM CST Sun Dec 22 2024

Valid 251200Z - 301200Z

...DISCUSSION...
A moderately amplified and more active/progressive southern-stream
pattern is still expected later this week, along with a general
northward fluctuation of low-level moisture across parts of Texas to
the Lower Mississippi Valley and Gulf Coast.

After a day of little or no severe-weather potential on Christmas
Wednesday/Day 4, severe risks are expected to increase into Days 5-7 Thursday-Saturday. A secondary upper trough is expected to emerge
from the Southwest deserts and moves toward the Ozarks/Deep South.
This could lead to at least a low-end multi-day severe risk in a
corridor from east/southeast Texas and the ArkLaTex to Lower
Mississippi Valley. In particular, Thursday/Day 5 could ultimately
warrant Slight Risk-caliber severe probabilities across
east/southeast Texas, especially if the more southern and more
severe-favorable ECMWF model runs become more apparent.

..Guyer.. 12/22/2024

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ACUS48 KWNS 230956
SWOD48
SPC AC 230955

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0355 AM CST Mon Dec 23 2024

Valid 261200Z - 311200Z

...DISCUSSION...
Severe-weather potential is still expected for Days 4-6
Thursday-Saturday, as an upper trough emerging from California and
the Southwest deserts moves toward the Ozarks/Deep South by
Thursday/Day 4. At least a low-end multi-day regional severe risk is
expected across south-central and east/southeast Texas towards parts
of the ArkLaTex, and possibly the Lower Mississippi Valley. In
particular, Thursday/Day 4 could ultimately warrant Slight
Risk-caliber severe probabilities across south-central to
east/southeast Texas although guidance variability persists, while objective/machine-learning guidance generally also persist with
sub-15 percent probabilities.

..Guyer.. 12/23/2024

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ACUS48 KWNS 241000
SWOD48
SPC AC 240959

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0359 AM CST Tue Dec 24 2024

Valid 271200Z - 011200Z

...DISCUSSION...
At least some severe-weather potential is expected across East Texas
and the Deep South for Friday/Day 4 and Saturday/Day 5. On
Friday/Day 4, a secondary shortwave trough may evolve across the
southern Plains in the wake of the shortwave trough related to
Thursday's/Day 3 severe potential. While some severe storms could
occur across east/southeast Texas toward the ArkLaTex on Friday/Day
4, details of available buoyancy are uncertain, especially given the
short periodicity between these mid-level systems. Similarly, a
severe storm risk could shift eastward toward the Lower
Mississippi/Mid-South on Saturday/Day 5, but confidence in 15+
percent probabilities is currently limited. Severe storm potential
is then expected to be relatively low into Days 6-8 Sunday-Tuesday.

..Guyer.. 12/24/2024

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ACUS48 KWNS 300933
SWOD48
SPC AC 300931

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0331 AM CST Mon Dec 30 2024

Valid 021200Z - 071200Z

...DISCUSSION...
Thunderstorm chances will likely be limited on D4/Thursday and
D5/Friday as airmass over the CONUS remains too cold and dry. Some
airmass modification may begin across the southern Plains late
d5/Friday or early D6/Saturday as a shortwave trough progresses
across the western CONUS. As the upper pattern trends more zonal
across the central CONUS, surface lee troughing will sharpen, with
low-level flow forecast to strengthen amid the increasing surface
pressure gradient. The approaching shortwave trough is expected to
continue its eastward progression into the Plains on D6/Saturday and
D7/Sunday, resulting in potential interaction with this return
moisture from central/eastern portions of TX/OK into the Lower MS
Valley. All aspects of the approaching shortwave trough remain
uncertain, with deterministic guidance showing large run-to-run
variability and notable difference between the GEFS and EPS. As
such, overall forecast confidence is low. However, the overall
trends suggests some severe potential may materialize late this
weekend into early next week.

..Mosier.. 12/30/2024

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ACUS48 KWNS 310923
SWOD48
SPC AC 310922

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0322 AM CST Tue Dec 31 2024

Valid 031200Z - 081200Z

...DISCUSSION...
Expansive ridging is forecast to gradually shift from the Plains
into the MS Valley and Southeast on D4/Friday, with stable
conditions prevailing.

A shortwave trough is expected to progress from the western Great
Basin through the Four Corners and into central/southern High Plains
on D5/Saturday, continuing eastward across central/southern Plains
and Mid/Lower MS Valley on D6/Sunday. Surface cyclogenesis appears
probable over the southern High Plains on D5/Saturday ahead of the
approaching shortwave, with a warm sector characterized by mid 60s
dewpoints likely to precede the resulting surface low and attendant
cold front. Thunderstorms are possible from central TX/OK eastward
through the Lower MS Valley on D6/Sunday, as the cold front
interacts with the moderately moist and buoyant air within the warm
sector. Deep-layer vertical shear is expected to be strong enough to
support organized storms (i.e. greater than 40 kt from 0-6 km).

Mid/upper level pattern is similar between the EPS and GEFS, but the
surface pattern has notable differences, with most GEFS members
favoring a slower and more southerly track to the surface low. This
is matched by the deterministic runs of the ECMWF and GFS, while the
Canadian splits the difference. Even though some severe appears
probable, these differences limit the forecast confidence, making it
difficult to ascertain the most likely corridor for severe
thunderstorms. Additionally, all of the deterministic guidance
continues to show notable run-to-run variability. All of these
factors combined with the extended range of the possible severe
(i.e. Day 6) result in too much uncertainty to delineate any risk
areas with this outlook.

The risk for thunderstorms will likely continue along the Gulf Coast
on D7/Monday as this system continues eastward. By D8/Tuesday, cold
and dry conditions are anticipated across the entire CONUS.

..Mosier.. 12/31/2024

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ACUS48 KWNS 010940
SWOD48
SPC AC 010939

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0339 AM CST Wed Jan 01 2025

Valid 041200Z - 091200Z

...DISCUSSION...
A shortwave trough is expected to progress from the western Great
Basin through the central Rockies and into central/southern Plains
on D4/Saturday, continuing eastward across the Mid/Lower MS Valley
on D5/Sunday. Surface cyclogenesis is anticipated ahead of this wave
over the southern High Plains on D4/Saturday, with the resulting low
tracking eastward across OK. Strengthening low-level southerly flow
ahead of this low will result in moderate moisture advection, with a
warm sector characterized by 60s dewpoints preceding the low and its
attendant cold front.

Thunderstorms are possible from central TX/OK eastward through the
Lower MS Valley on D5/Sunday, as the cold front interacts with the
moderately moist and buoyant air within the warm sector. Deep-layer
vertical shear is expected to be strong enough to support organized
storms (i.e. greater than 40 kt from 0-6 km). Latest deterministic
runs of the ECMWF and GFS continued to show notable differences,
particularly with the overall speed of the shortwave and its
associated surface low. However, EPS and GEFS members shows greater consistency, with numerous members placing the surface low over the
AR vicinity by D5/Sunday evening. Consequently, there is increased
confidence that the environment over the Lower MS Valley will
support severe thunderstorms D5/Sunday afternoon, with the threat
potentially continuing into the Southeast overnight.

The risk for thunderstorms will likely continue across the Southeast
on D6/Monday as this system continues eastward. Cold and dry
conditions are anticipated across the entire CONUS on D7/Tuesday and D8/Wednesday.

..Mosier.. 01/01/2025

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ACUS48 KWNS 020918
SWOD48
SPC AC 020916

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0316 AM CST Thu Jan 02 2025

Valid 051200Z - 101200Z

...DISCUSSION...
Medium-range guidance is in relatively good agreement that a
shortwave trough will extend from western/central KS into the TX
Hill Country early D4/Sunday morning. This shortwave is then
forecast to progress northeastward throughout the day, likely
reaching the Mid MS Valley by D5/Monday morning. An associated
surface low will move just ahead of the parent shortwave, with an
attendant cold front sweeping eastward across east TX and Lower MS
Valley. A warm sector characterized by low to mid 60s dewpoints will
precede this front, which should be sufficient for modest buoyancy
despite a relatively warm profile and poor lapse rates.

Thunderstorm development is anticipated along the front, with some
potential for isolated discrete storms ahead of the front as well.
Moderate to strong mid-level flow will extend across the warm
sector, resulting in deep-layer vertical shear strong enough to
support organized storms (i.e. 0-6 km bulk shear from 40 to 50 kt).
General expectation is for the development of a fast-moving
convective line capable of strong to severe gusts along the cold
front, supported by modest buoyancy and deep-layer shear orthogonal
to the front. Strengthening low-level flow (i.e. 50 to 60 kt at 850
mb) could also support enough low-level shear for line-embedded
circulations as well.

Some thunderstorms will remain possible across the Southeast on
D5/Monday as the front continues eastward. However, limited
low-level moisture ahead of the front should limit the severe
thunderstorm threat.

From D6/Tuesday through D8/Thursday, cold and stable conditions are
expected to preclude thunderstorm development across the CONUS.

..Mosier.. 01/02/2025

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