SPC AC 151642
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1042 AM CST Sat Feb 15 2025
Valid 151630Z - 161200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
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.
...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.
..Smith/Supinie.. 02/15/2025
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