4/26/2023 - Severe Weather Discussion Thread Apr 26, 2023 5:21:50 GMT -6
Post by SKYSUMMIT on Apr 26, 2023 5:21:50 GMT -6
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
0100 AM CDT Wed Apr 26 2023
Valid 271200Z - 281200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTHERN
LOUISIANA INTO SOUTHERN ALABAMA AND THE WESTERN FLORIDA PANHANDLE...
Scattered severe storms are expected Thursday mainly from southern
Louisiana into the Florida Panhandle. Damaging gusts, large hail,
and a few tornadoes will all be possible.
A positive-tilt upper trough will move from the southern Plains
toward the lower and middle MS Valley on Thursday, with moderate
midlevel southwesterlies overspreading much of the Southeast.
Meanwhile, a compact shortwave trough will move quickly
south/southeastward from western MT into WY, reaching the Four
Corners area by 12Z Friday.
Ahead of the southern trough, low-level flow will gradually veer to
southerly, resulting in increased moisture return across the Gulf
Coast states. A weak low will move roughly from the Arklatex to the
lower OH Valley through 00Z, and into OH by 12Z Friday. A cold front
(likely augmented by convective outflow) will trail southwestward
from the low, and will provide a focus for scattered to numerous
storms throughout the day. Southerly winds averaging around 35 kt
will maintain an unstable air mass, which will combine with
favorable deep-layer shear to support a severe threat, with all
modes of severe possible.
...Sabine Valley eastward into western Georgia...
A substantial line of storms is likely to be ongoing Thursday
morning, stretching from the lower Sabine Valley into western MS. If
anything, models may be too slow with this line, given historical
tendencies. Upper 60s F dewpoints will surge north across LA as well
as southern MS and AL, resulting in MLCAPE in excess of 2000 J/kg,
the highest values being over LA. Favorable deep-layer shear,
seasonably steep midlevel lapse rates and southerly flow at 850 mb
should support strengthening of this convective system as it
proceeds east throughout the period. In addition to damaging winds,
large hail will be possible, despite the mainly linear storm mode
and due to the aforementioned environmental factors. A few tornadoes
cannot be ruled out, especially if portions of the line can become
segmented. Isolated supercells cannot be ruled out ahead of the line
as the air mass moistens and destabilizes. A corridor of higher
severe probabilities could eventually be needed, dependent on storms
trends Thursday morning.
...AR into western TN...
Storm coverage is expected to be isolated from AR into TN, north of
the primary convective system. Cold air aloft, sufficient moisture
and pockets of heating may support isolated thunderstorms near the
weak surface low and in association with the midlevel vorticity
maximum. Effective shear around 50 kt, modest instability but weak
winds in the lowest few km may support marginal hail or wind during
Strong surface heating and cooling aloft with the upper trough will
lead to weak instability, and a steep-lapse-rate environment.
Forecast soundings depict inverted-v structures which may support
downdraft potential. The overall threat appears low, however, due to