SPC 1300Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0700 AM CST Tue Feb 23 2021

Valid 231300Z - 241200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
A few thunderstorms will be possible across the Pacific Northwest
and northern Rockies this afternoon and evening.

...Synopsis/Discussion...
Broad cyclonic flow aloft will prevail across the northwest U.S.
through the period, with an embedded mid-level impulse expected to
pivot around the cyclonic flow and traverse the Pacific Northwest
during the late afternoon and evening hours. While temperatures are
expected to be sub-freezing through the troposphere at locations in
higher elevations, lower terrain areas may experience above freezing
temperatures at the low levels, allowing for enough charge
separation to support at least a few lightning flashes across parts
of the Pacific Northwest.

In addition, a mid-level trough will be ejecting into the Atlantic
while a southward-sagging surface cold front moves across the
southern Florida Peninsula, with cooler and drier air ushering in
from behind. The surface cold front is expected to undergo
frontolysis across the Peninsula, with weakening low-level
convergence and a lack of greater buoyancy in the -10 to -30C
charge-separation layer contributing to negligible thunderstorm
chances. The idea of limited lightning potential is further
substantiated by the 12Z observed sounding from Miami which sampled
weak mid-level lapse rates and limited overall buoyancy.

..Guyer.. 02/23/2021

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