Southern Severe Weather Threat (Thursday/Friday)

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SPC AC 031611

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1011 AM CST Fri Mar 03 2023

Valid 031630Z - 041200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS TN/OH VALLEYS
TO THE SOUTHERN APPALACHIANS...

...SUMMARY...
Numerous tornadoes and scattered swaths of severe damaging winds are
probable into this evening from the Tennessee to Ohio Valleys
towards the southern Appalachians. A few tornadoes may be strong
(EF-2) with the greatest chance across parts of Kentucky and
Tennessee.

...TN to OH Valleys and the central/southern Appalachians...
Two primary areas of convective activity are ongoing from MS/AL/TN
border area northwest to the confluence of the MS/OH Rivers. Leading
pre-frontal squall, low-topped near the central MS/AL border with
progressively deeper tops northward, will likely persist
east-northeast this afternoon and reach the southern Appalachians by
early evening. With broken cloudiness across AL and richer
boundary-layer moisture, sampled by the 12Z LIX sounding, advecting
north from the central Gulf Coast, this QLCS should ingest the
northern gradient of peak surface-based buoyancy. This should result
in intensification of the squall line with embedded QLCS tornadoes
and damaging winds as the primary hazards.

Farther north, broken convective bands are evident along the
northern periphery of the warm sector near the MS/OH Rivers
confluence, close to the deep surface cyclone. A robust surface
pressure rise-fall couplet and the extreme low to deep-layer shear
should compensate for the meager surface-based buoyancy and likely
yield a mix of low-topped supercells and quasi-linear bowing
segments, as convection rapidly spreads east-northeast. Tornadoes
should be realized in sustained supercells and line-embedded
mesovortices, a few of which could be significant. Given the
supercell wind profiles and morning CAMs suggesting more broken
convection, damaging winds will probably consist of scattered swaths
of severe gusts from 60-80 mph.

Severe potential today will be limited on the southern part by
weakening DCVA and frontal convergence with southward extent, on the
northern end by northward loss of boundary-layer destabilization
away from the warm-frontal zone, and to the east by loss of both
daytime heating and overall lift. As such, the unconditional
probability gradient is kept rather broad on both sides, though the
actual southern/northern/eastern cutoffs of severe could be abrupt.

..Grams/Wendt.. 03/03/2023

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