Valid 222000Z – 231200Z
…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE UPPER TEXAS COAST INTO CENTRAL MS THROUGH THIS EVENING….
Strong to briefly severe thunderstorms are possible from southeast
Texas to central Mississippi through tonight.
…20z Update – East TX to Central MS…
The previous outlook remains on track and no changes have been made
to severe probabilities. The 10% General Thunder line has been
modified across parts of eastern TX to western KY to account for
latest trends in radar/lightning data. The surface cold front
extends from northeast MS southwestward into northern LA, then
south/southwest toward the Middle and Upper Texas Coast. Some
pockets of broken cloudiness have resulted in weak instability (less
than 1000 J/kg MLCAPE) across western LA and deeper convection was
developing along the cold front per latest visible imagery.
Prefrontal showers and thunderstorms will limit downstream
thermodynamic environment despite favorable deep layer shear for
organized storms. A couple of short-lived strong storms could
produce some strong wind gusts. Given the depth of the moist
boundary layer and backed low level flow ahead of the front, a
brief/weak tornado cannot be ruled out.
.PREV DISCUSSION… /ISSUED 1022 AM CST Fri Nov 22 2019/
…Lower MS/TN Valley regions through early Saturday…
A lead shortwave trough over OK this morning will eject
east-northeastward and weaken in confluent flow regime aloft, while
an upstream speed max over the southern Rockies progresses eastward
to the Ark-La-Tex by 23/12z. At the surface, a cold front will move
slowly southeastward across the Ark-La-Miss and southeast TX today.
A weak surface cyclone is expected to develop along the front
tonight across the lower MS Valley and then move northeastward to
the TN Valley by Saturday morning. The warm sector south of the
front is characterized by boundary-layer dewpoints ranging from the
mid 60s in west central MS to the lower 70s along the upper TX
coast, with weak-moderate buoyancy (MLCAPE 500-1000 J/kg). The
relatively larger buoyancy will likely be confined to along and
south of a pre-frontal convective band from extreme southeast TX
into central LA today, where the highest dewpoints will reside and
some surface heating will occur in cloud breaks.
Since little in the way of cyclogenesis is expected today, low-level
shear is likely near peak this morning and should weaken some this
afternoon in the warm sector. This leaves an environment with
modest low-level shear and sufficient deep-layer shear/buoyancy for
some embedded supercells with a low-end damaging wind and/or tornado
threat. Convection will persist through tonight and spread into
northern AL, though lingering static stability near the ground
should limit any threat for strong/severe storms this far northeast.