SPC AC 201221
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0621 AM CST Mon Nov 20 2017
Valid 201300Z - 211200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
The risk for severe thunderstorms appears negligible across the U.S.
today through tonight.
Gradual amplification of the western ridge/eastern trough pattern is
expected through Tuesday. An embedded shortwave trough over the Rio
Grande Valley will progress to the central Gulf of Mexico by
tonight, with some potential for very weak surface cyclogenesis
across the eastern Gulf in association with ascent preceding the
wave and air mass modification over the loop current. Isolated
lightning flashes have been observed this morning with convection
crossing the Rio Grande, and 12z soundings from CRP/BRO confirm
sufficient buoyancy rooted near or above 700 mb to sustain a
thunderstorm threat through the morning across deep south TX.
Otherwise, low-level moistening/destabilization is expected across
the southeast FL coast as a front stalls and then retreats back to
the north tonight. Only shallow convective showers are expected
today across southeast FL, but moistening could become sufficient
for deeper convection and isolated lightning flashes overnight.
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