SPC 0700Z Day 2 Outlook

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1258 AM CST Wed Feb 17 2021

Valid 181200Z - 191200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE FLORIDA PANHANDLE...SOUTHEASTERN ALABAMA...SOUTHERN/CENTRAL
GEORGIA...AND COASTAL SOUTH CAROLINA...

...SUMMARY...
Isolated strong to severe thunderstorms may occur across parts of
the Southeast on Thursday. A couple tornadoes and isolated damaging
wind gusts should be the main threats.

...Southeast...
A large-scale upper trough is forecast to move eastward from the
Plains to the MS Valley vicinity on Thursday. A belt of enhanced
mid/upper-level southwesterly winds will overspread much of the
Southeast to the Mid-Atlantic through the period. At the surface, a
weak low over the north-central Gulf of Mexico should develop
northeastward across the FL Panhandle and into southern GA by
Thursday evening. A warm front is forecast to lift northward across
southern GA in the same time frame. A cold front attendant to the
surface low will eventually sweep eastward across northern FL and
southern GA Thursday afternoon/evening and continuing through the
overnight.

A broken band of strong to potentially severe storms may be ongoing
Thursday morning across parts of the western FL Panhandle and
vicinity. Low-level moisture is forecast to gradually increase
across the warm sector ahead of this morning convection, with mid to
upper 60s surface dewpoints likely by mid afternoon. Diurnal heating
will probably be fairly muted, but it should still support weak
boundary-layer instability along/south of the warm front by Thursday
afternoon. MLCAPE around 250-750 J/kg appears probable, with poor
mid-level lapse rates likely limiting more robust destabilization.
Much of the large-scale forcing associated with the approaching
upper trough and related mid/upper-level jet may remain mostly to
the north of the surface warm sector. Still, strong flow aloft will
likely foster 40-50 kt of effective bulk shear, which will be more
than sufficient for organized severe storms. Current expectation is
for storms to spread eastward through the afternoon across the FL
Panhandle and southern GA, eventually reaching parts of
central/eastern GA and coastal SC by early Thursday evening.

Given the weak but adequate instability and strong low/mid-level
flow, isolated damaging winds may occur with both discrete and
linear convection. A couple tornadoes also appear possible with any
supercells that can form, as a 40-45 kt south-southwesterly
low-level jet will overlie much of the warm sector through the day,
enhancing effective SRH. This tornado threat may focus along/near
the northward-developing warm front in southern/central GA and
coastal SC. Storms should eventually encounter a less unstable
airmass with eastward extent into northern FL and coastal GA, and a
general weakening trend should occur Thursday evening/night.
Finally, low-level moisture return father north across SC and
eastern NC appears more muted in latest guidance, suggesting any
isolated/marginal wind threat should remain close to the coast.

..Gleason.. 02/17/2021

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