SPC 0830Z Day 3 Outlook

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0208 AM CST Mon Dec 21 2020

Valid 231200Z - 241200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST
TEXAS ACROSS THE CENTRAL GULF COAST INTO THE WESTERN FLORIDA
PANHANDLE...

...SUMMARY...
Isolated severe thunderstorms are possible from southeast Texas
across the central Gulf Coast into the western Florida Panhandle.

...Synopsis...
A deep surface low is forecast to be centered over east-central
MN/northwest WI early Wednesday morning. A strong cold front will
extend southwestward from the low across the Ozark Plateau and into
north-central TX before arcing more westward through the TX Permian
Basin. This front is expected to surge southward/southeastward
throughout the day as the parent surface low moves eastward over the
Upper Great Lakes and gradually occludes.

At the same time, upper troughing initially extending from the
Canadian Prairie Provinces into the central Rockies is expected to
deepen significantly as it progresses eastward. Additionally,
mid-level flow surrounding the trough will strengthen. By early
Thursday morning, a large corridor of 100+kt 500-mb winds is
expected to extend from the Lower MS Valley through the Upper Great
Lakes into southeastern Ontario. 

Modest moisture advection associated with this system will likely
result in low to mid 60s dewpoints from central/east TX into
southern AL/MS and the FL Panhandle ahead of surging cold front.
Widespread cloud cover will temper daytime heating and, along with
poor lapse rates, will contribute to limited buoyancy. Even so,
strong vertical shear supports organized storm structures with any
mature/persistent updrafts. Based on current guidance, highest
probability of severe storms appears to be across the western FL
Panhandle early Thursday when the strengthening low-level flow
aligns with the limited buoyancy.

..Mosier.. 12/21/2020

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