Day 1 Severe Weather Outlook

Valid 051300Z – 061200Z


A few severe thunderstorms with damaging winds, a couple of
tornadoes, and isolated large hail will be possible today across
north Florida and southern Georgia.

…North FL/southern GA today…
A midlevel trough over the lower MS Valley will continue to
accelerate eastward to the southeast Atlantic coast and lose
amplitude by early tonight, as a northern stream trough digs
southeastward and amplifies over the OH Valley/Great Lakes region by
tonight. In advance of the southern shortwave trough, a weak
surface cyclone will move east-northeastward along a stalled front
from the FL Panhandle to north FL/southeast GA by mid-late
afternoon. The corridor along the boundary will be the primary
focus for severe thunderstorms today.

Convection this morning has been confined to the warm advection zone
above the shallow cool air mass across AL/GA, where a couple of
elevated left-moving supercells have been observed. Elevated
convection is likely to persist through the day and spread eastward
from southeast AL/southwest GA this morning to southeast GA/southern
SC this afternoon. Sufficient buoyancy (MUCAPE near 1000 J/kg) and
effective bulk shear in excess of 40 kt will support a low-end
threat for large hail with storms north of the front.

The residual outflow across north FL from prior convection should
erode northward a few tiers of counties to the position of the
deeper baroclinic zone across southern GA, as the surface low moves
east-northeastward this afternoon. Surface heating and
boundary-layer dewpoints of 68-70 F along and south of the front
will boost MLCAPE to near 1500 J/kg by afternoon, with relatively
small convective inhibition in a zone along the front and
immediately in advance of the surface cyclone. Deep-layer shear
will be favorable for supercells in this zone, and an increase in
low-level southwesterly flow to near 50 kt will result in enlarged
hodographs and effective SRH near 300 m2/s2. Forecast hodographs
conditionally support a supercell tornado threat, with the main
uncertainty being weak forcing for ascent in the unstable surface
warm sector. Assuming surface-based storms can form along the north
edge of the warm sector this afternoon, there will be an attendant
threat for a couple of tornadoes and damaging winds, as well as
isolated large hail.

..Thompson/Jewell.. 03/05/2020


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