ACUS01 KWNS 152001
SWODY1
SPC AC 151959
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0159 PM CST Sat Feb 15 2025
Valid 152000Z - 161200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
LOWER MISSISSIPPI VALLEY...MID SOUTH AND SOUTHEAST...
...SUMMARY...
Severe thunderstorms are expected from parts of far east Texas into
much of the lower Mississippi Valley and Southeast this afternoon
through the overnight. Several tornadoes and scattered to numerous
damaging wind gusts should be the primary threats. A few strong
tornadoes are also possible.
...20Z Update...
The prior outlook remains largely unchanged. The well-defined
shortwave trough and 80-100 kt mid-level jet are evident on WV
imagery moving across west-central TX. Rapid surface cyclogenesis is
expected later this afternoon/evening as the upper trough/jet
overspread a broad frontal cyclone over the eastern Red River and MS
Valley vicinity. Initial semi-discrete development along the warm
front is expected this afternoon with continued heating and the
approach of the stronger cold front over western AR. Southwesterly
flow parallel to the frontal zone and little inhibition should
support quick upscale growth into a more linear mode. Strong
tropospheric flow (700 mb winds of 55-75 kt) will support the
potential for widespread damaging wind gusts with the line, while
strong shear could also support mesovortex tornadoes.
Partial clearing in the wake of earlier convection east of the
frontal zone will support diurnal heating and steepening of some low
and mid-level lapse rates across far eastern AR, northwestern MS and southwestern TN. The decrease in inhibition while forcing for ascent
is still relatively weak may support some potential for more
discrete development. While it remains unclear if this will occur,
the very strong low-level shear (0-1 km BWD 40+ kt) would support a
conditional significant tornado threat with any prefrontal/warm
sector supercells able to evolve.
...Gulf Coast and Southeast...
The strongly forced squall line is forecast to translate rapidly
across much of the Southeast late this evening and overnight. Strong
low-level warm air advection and broad ascent ahead of the upper
trough could support isolated discrete development, and a some
strong tornado potential ahead of the line, especially farther south
across southern MS/AL. However, poor lapse rates aloft lend low
confidence to any discrete supercells being maintained. Damaging
gusts and line-embedded tornado will remain possible overnight. For
more info see the prior outlook.
..Lyons.. 02/15/2025
.PREV DISCUSSION... /ISSUED 1042 AM CST Sat Feb 15 2025/
...Synopsis...
Water-vapor imagery this morning shows a potent mid-level trough
over the Permian Basin pivoting east through the base of a larger
scale trough forecast to shift from the Rockies east into the MS
Valley. A complex surface pattern is evident with a low over OK
with an accompanying trailing cold front, while a maritime
boundary/residual frontal zone is draped over east TX arcing
northeastward into the MS/AR/TN border region and then southeastward
into the northeast Gulf of America. As the cyclone consolidates and
moves eastward this afternoon into AR, the aforementioned composite
boundary will advance northward as a warm front into the Mid South
and towards the southern Appalachians late. The cold front is
forecast to push southeast and overtake the western portion of the
warm sector late today into tonight and provide a focus for numerous
developing thunderstorms in the form of a squall line.
...East Texas into the Lower Mississippi Valley and Southeast...
Strong low-level warm advection has resulted in scattered
showers/thunderstorms mainly north of the warm front from AR east
into TN. Southerly flow will promote poleward moist advection with
60s deg F dewpoints spreading north across the lower MS Valley into
parts of the Mid South. The destabilizing warm sector will remain
capped during the day before stronger large-scale ascent approaching
from the west results in a extensive thunderstorm development from
the Ark-La-Tex northeast into eastern AR/western TN/KY. Filtered
daytime heating and low-level moistening will aid in the development
of around 500-1000 J/kg of MLCAPE by mid to late afternoon.
Surface-based thunderstorms are forecast to develop by mid afternoon
near or on the cold front from east TX into the Mid South. Only a
narrow window of opportunity for supercells will likely occur before
rapid upscale growth into an extensive squall line by early evening.
Strong 0-3 km shear, aided by a 45-55+ kt low-level jet, will easily
aid updraft rotation and organized severe thunderstorms.
Ample low-level shear will support a threat for several
line-embedded tornadoes beginning from late this afternoon through
early Sunday morning. The potential for supercells ahead of the line
will likely remain limited but will be greatest perhaps over the
southern parts of MS/AL tonight. However, if cellular structures
are maintained in the large-scale thunderstorm band, an accompanying
risk for tornadoes may focus there and with any bowing inflections
in the line. Given the low CAPE/high shear setup with relatively
modest lapse rates and moist profiles, scattered to numerous
severe/damaging winds will likely occur with the squall line as it
matures. Have increased damaging wind probabilities from parts of
MS into AL where confidence is greatest for damaging gusts later
tonight. A continued tornado/damaging wind risk will become
increasingly confined to the Gulf coastal plain late tonight into
the early Sunday morning hours.
$$
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