Day 1 Severe Weather Outlook

Valid 132000Z – 141200Z


A tornado or two, isolated damaging winds, and marginal hail are
possible centered on the eastern panhandle and north Florida into
far southern Georgia, mainly during the late evening and overnight.

Forecast reasoning — as communicated in earlier outlooks — remains
generally reflective of the evolving weather over the southeastern
states, though risk appears to be slightly lesser than previously
expected. The slight risk is being decreased in areal extent in
this update, as the damming/wedge front has pushed
south-southwestward across the Florida Panhandle. Thus suggests
that the forecast/weak cyclogenesis will more likely occur from the
Florida Big Bend region northeastward across far southern Georgia,
and thus severe risk appears lesser across the Panhandle.

Otherwise, limited potential for a couple of severe storms remains
through the overnight hours, so the remainder of the outlook will
remain unchanged at this time.

..Goss.. 12/13/2019

.PREV DISCUSSION… /ISSUED 1025 AM CST Fri Dec 13 2019/

…North FL/far southern GA vicinity…
No changes have been to the prior categorical outlook given
relatively substantial differences in latest guidance for the D1
time frame.

A shortwave trough over the south-central states will amplify as a
vigorous backside mid-level jet ejects into and through the base of
the trough by early morning. While primary surface cyclone
development should occur downstream of the central Appalachians into
the Mid-Atlantic States, a secondary low may attempt to form along
the quasi-stationary front draped across the northeast Gulf and
north FL. The 15Z RAP is more aggressive compared to the 12Z NAM
with this scenario, resulting in a more buoyant warm sector
spreading farther north. Forecast soundings in the Tallahassee to
Brunswick, GA corridor illustrate these differences. Considering the
stable CP air mass currently entrenched farther north, it seems
plausible that surface-based destabilization will struggle where
ascent aloft will be strong. As such, the bulk of convective
development may remain north of the warm sector.

Across the northern FL peninsula, the time window for moderate
surface-based buoyancy to be coincident with sufficiently enlarged
low-level hodographs appears relatively confined. However,
deep-layer speed shear will be strong and supportive of mid-level
updraft rotation should convection be sustained into the warm sector
along a progressive cold front during the early morning. This may
yield a couple tornadoes along with isolated to scattered damaging
winds and locally severe hail.


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