SPC 0830Z Day 3 Outlook

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0229 AM CST Tue Dec 22 2020

Valid 241200Z - 251200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS FAR EASTERN
SC...COASTAL NC...AND FAR SOUTHEAST VA...

...SUMMARY...
Isolated severe thunderstorms are possible across portions of the
Florida Panhandle and adjacent southeast Alabama and southwest
Georgia early Thursday. Severe thunderstorms are also expected
across the Mid-Atlantic States Thursday afternoon and evening.

...Synopsis and Discussion...
Deep upper troughing is forecast to extend from northwestern Ontario
into central Mexico early Thursday morning. Strong flow aloft will
extend throughout the periphery of this upper trough. Shortwave
trough embedded within the base of this larger trough will likely be
moving through the Ozark Plateau and southern Plains early Thursday
morning. Continued eastward/northeastward progression of this
shortwave is expected, with the parent upper trough also progressing
eastward. Evolution of the embedded shortwave will help induce a
neutral tilt to the upper trough by Thursday afternoon, and a
slightly negative tilt and closed upper circulation over the OH
Valley by late Thursday night/early Friday morning.

The maturing process of the upper trough will also result in further
strengthening of the winds throughout its periphery. By early Friday
morning, 100+ kt 500-mb winds will likely extend from the mid MS
Valley southeastward/eastward through the base of the trough over
the Southeast and then back northeastward into the Northeast. Very
intense low-level flow is also expected, with 60+ kt at 850-mb
extending from the Carolinas through the Mid-Atlantic into Quebec. 

Modest severe potential is anticipated early Thursday along and
ahead of the across the FL Panhandle and southeast AL/southwest GA.
In this region, modest instability and strong flow will likely
support a few strong/severe storms. An additional area of
potentially greater severe potential is expected farther north
across the Mid-Atlantic. In this area, a deepening surface low and
strong low-level flow will contribute to robust moisture return as
well as large, looping low-level hodographs. Strong buoyancy is not
expected, but given the very strong vertical shear, even modest
surface-based instability will likely result in severe storms.
Strong to severe storms along the front appear likely, with some
potential for warm-sector storms as well. Given the anticipated
kinematic environment, any deeper warm-sector storms would likely
become supercellular.

..Mosier.. 12/22/2020

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