Deep South Severe Weather Thread (Enhanced)

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Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1121 AM CDT Wed Oct 27 2021

Valid 271630Z - 281200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS
AFTERNOON/EVENING ACROSS SOUTHERN LA AND COASTAL MS...

...SUMMARY...
Scattered severe thunderstorms capable of producing damaging winds
and tornadoes, some of which could be strong this afternoon, will
continue spreading eastward across Louisiana to southern Mississippi
through this evening, and across the northeast Gulf coast overnight.

...Northern Gulf coast through tonight...
A midlevel trough over the southern Plains this morning will move
eastward toward the lower MS Valley by early Thursday, while
evolving into a closed low. An associated surface cyclone will
likewise move slowly eastward while occluding across AR tonight, as
a cold front translates eastward from east TX across LA to MS. To
the east, a warm front will move northward across southern LA/MS
today and southern AL/FL Panhandle by tonight. A maritime tropical
air mass is present south of the warm front, with boundary-layer
dewpoints in the low-mid 70s, which is contributing to moderate
buoyancy (MLCAPE of 1000-2000 J/kg this morning across the northwest
Gulf coast. The stronger inland destabilization is expected today
across southern LA as the tropical air mass spreads inland beneath
the east fringe of the steeper midlevel lapse rate plume through the
afternoon as the warm sector spreads northward across southern
LA/MS.

Wind profiles are favorable for tornadic supercells along the north
edge of the warm sector, with effective bulk shear of 40-50 kt and
effective SRH of 200-300 m2/s2, per recent soundings/VWPs and
short-term model forecasts. The potential for occasional discrete
supercells in the warm sector will spread eastward across southern
LA, with an attendant threat for a couple of strong tornadoes near
the warm front. Within the pre-frontal squall line, damaging winds
can be expected with bowing segments, and a tornado threat will also
persist with embedded mesovortices. A similar regime will spread
eastward to southern MS/AL and the FL Panhandle this evening into
tonight, though with slightly weaker buoyancy after the diurnal
heating cycle.

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