000
ACUS03 KWNS 170801
SWODY3
SPC AC 170800

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0200 AM CST Mon Jan 17 2022

Valid 191200Z - 201200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
THE UPPER TEXAS COAST INTO THE LOWER MISSISSIPPI VALLEY...

...SUMMARY...
Isolated severe thunderstorms may occur Wednesday from parts of the
upper Texas Coast into the lower Mississippi Valley.

...Upper Texas Coast into the Lower Mississippi Valley...
A low-amplitude, southern-stream shortwave trough should eject
quickly eastward from the southern High Plains to the lower MS
Valley on Wednesday. At the surface, a weak low initially in the
vicinity of the ArkLaTex is likewise forecast to develop towards the
Mid-South through the day, while a strong cold front moves southward
across the southern Plains and lower MS Valley in its wake. The
return of a partially modified Gulf airmass should continue ahead of
the cold front across much of the TX Coastal Plain and into parts of
the lower MS Valley. Due to a prior frontal passage shunting rich
low-level moisture well south into the Gulf of Mexico, this moisture
return is forecast to remain fairly muted, with generally mid 50s to
low 60s surface dewpoints expected over land.

With only modest diurnal heating, weak instability capable of
supporting surface-based convection should develop in a fairly
narrow corridor ahead of the cold front, extending from the upper TX
Coast northeastward into portions of LA/MS. Fairly long, straight
hodographs and strengthening winds with height through mid levels
shown in various NAM forecast soundings across this region suggest
around 40-50 kt of deep-layer shear should be present. This shear
will likely support thunderstorm organization, and some supercell
potential with initial development Wednesday afternoon.

Isolated large hail may occur with this activity, although mid-level
lapse rates are not expected to be overly steep. With time,
convection should grow upscale along/ahead of the front as both move
south-southeastward. Damaging winds should become a greater concern
as this mode transition occurs. A tornado or two also appears
possible, as a 30-40 kt southwesterly low-level jet should linger
over the warm sector through much of the day, enhancing low-level
shear. Eventually, the convection should outpace the modest
low-level moisture return, and a weakening trend should occur
Wednesday evening/night across southern LA/MS into AL.

..Gleason.. 01/17/2022

$$