ACUS01 KWNS 181301
SWODY1
SPC AC 181259

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0659 AM CST Mon Nov 18 2024

Valid 181300Z - 191200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN PLAINS...AND FROM PORTIONS OF EAST TEXAS INTO LOUISIANA
AND FAR SOUTHERN ARKANSAS...

...SUMMARY...
Thunderstorms may continue to produce occasional strong to severe
gusts and perhaps a couple brief tornadoes across parts of north
Texas into central Oklahoma this morning. A threat for a few
tornadoes and damaging winds will also exist this afternoon and
evening from parts of east Texas into Louisiana and vicinity.

...Synopsis...
A negatively tilted shortwave trough over the southern High Plains
this morning will eject northeastward across the central Plains and
mid MO Valley through this evening. Attendant 80-100 kt mid-level
jet will likewise overspread OK/KS into western MO by late
afternoon, while a strong (50-60+ kt) southerly low-level jet aids
in northward moisture transport across parts of the southern/central
Plains and lower/mid MS Valley. At the surface, a deep low over
western OK will develop northeastward through the day in tandem with
the ejecting shortwave trough, eventually reaching the Upper Midwest
late tonight. A related cold front will sweep quickly eastward
across the southern/central Plains and into the mid MS Valley
through the period, before decelerating over the lower MS Valley
late tonight into early Tuesday morning.

...Southern Plains...
With low-level winds remaining very strong per area VWPs (up to
50-60 kt at 1 km AGL), an ongoing QLCS across central/southern OK
into north-central TX may continue to pose a risk for occasional
strong to severe winds in the short term this morning as it moves
east-northeastward. Ample low-level shear will also support a
continued threat for embedded circulations and a couple brief QLCS
tornadoes this morning. This line is expected to outpace better
low-level moisture return and already weak instability in the next
couple of hours (see very weak surface-based instability in 12Z
soundings from OUN/FWD). Accordingly, nearly all guidance shows
gradual weakening of the line over the next several hours as it
moves into eastern OK and northeast TX. Still, at least an isolated
threat for strong to damaging winds and perhaps a tornado could
persist, even as the thermodynamic environment becomes increasingly
marginal with eastward extent.

...East Texas into the Lower Mississippi Valley...
The southern portion of the squall line along/ahead of the cold
front should tend to remain weak through early afternoon, before
potentially restrengthening by mid/late afternoon into the early
evening. This should occur as the line/cold front encounters a more
buoyant airmass across parts of east TX into LA and southern AR,
where MLCAPE may reach up to 500-1000 J/kg with daytime heating,
even though mid-level lapse rates will remain poor. This region will
remain displaced well south of better forcing associated with the
ejecting shortwave trough. Even so, strengthening mid-level
southwesterly flow through the day will support 40-50 kt of
deep-layer shear and some threat for supercells ahead of the front.
Sufficient southerly low-level winds will also support adequate 0-1
km shear and a threat for a few tornadoes. Most high-resolution
guidance shows either the line restrengthening and/or supercells
developing ahead of it by late afternoon. Have therefore included a
Slight Risk from parts of east TX into LA and vicinity to account
for this potential.

...Central Plains/Ozarks into the Mid Missouri Valley...
Later today, a secondary area of thunderstorms may form closer to
the surface low and behind the initial QLCS from north-central OK
into central/eastern KS and eventually the mid MO Valley. This
convection may develop in a modestly steep mid-level lapse rate
environment amid more unidirectional southwesterly deep-layer flow
near the exit region of the mid-level jet. Even though instability
will remain weak, a couple of strong to severe thunderstorms may
pose an isolated risk for gusty winds, a tornado, and perhaps
marginally severe hail. Based on latest guidance trends, have
expanded the Marginal Risk northward some to include parts of the
mid MO Valley.

..Gleason/Kerr.. 11/18/2024

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