SPC AC 090712

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0212 AM CDT Fri Apr 09 2021

   Valid 111200Z - 121200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF
   FLORIDA TO THE MID-ATLANTIC COAST...

   ...SUMMARY...
   Isolated strong to severe thunderstorms are possible on Sunday from
   parts of Florida toward the Mid-Atlantic coast.

   ...Synopsis...

   A compact upper low and attendant trough over the Midwest/Great
   Lakes vicinity will pivot northward into Ontario and western Quebec
   on Sunday. Meanwhile, a weak shortwave impulse embedded in westerly
   flow over the Gulf Coast vicinity will track eastward toward the
   FL/GA/SC through Sunday evening. This should maintain moderate
   deep-layer flow over FL into southern GA and coastal SC, becoming
   weaker with northward extent. At the surface, upper 50s to 60s F
   dewpoints will extend northward from northern FL into the NC/VA
   coastal plain, east of a cold front. The exact position of the cold
   front, and where better-quality moisture may exist from southern GA
   northward through southeast VA, remains in question given periods of
   thunderstorms and an extensive southeastern U.S. QLCS forecast
   during the Day 1/Fri and Day 2/Sat periods. Nevertheless, the
   overall pattern should support at least a marginal risk for severe
   thunderstorms from FL into eastern NC/southeast VA.

   ...FL...

   The risk of isolated severe thunderstorms appears possible across
   northern/central FL on Sunday. Low to mid 60s F dewpoints will be in
   place ahead of a cold front. Modest midlevel lapse rates will
   contribute to MLCAPE around 1000-2000 J/kg. Low/midlevel flow will
   be somewhat modest, around 20-30 kt south/southwesterly winds
   through 850 mb, increasing to around 30-35 kt around 850-700 mb.
   Nevertheless, veering wind profiles will result in effective shear
   greater than 40 kt, favoring some supercell potential. Given weaker
   low-level flow, hodographs will remain rather small. A tornado or
   two, along with locally strong gusts and perhaps some small hail
   will be possible with this activity.

   ...GA into eastern NC/southeast VA...

   At least a conditional threat for isolated severe storms will exist
   on Sunday. Forecast guidance varies on the degree of low-level
   moisture and instability across the region, resulting in some
   uncertainty. Nevertheless, forecast soundings indicate a deeply
   mixed boundary layer with steep low level lapse rates will be
   present. Combined with weak instability and adequate effective
   shear, some threat for locally damaging gusts will be possible with
   any thunderstorm activity Sunday afternoon through early evening.

   ..Leitman.. 04/09/2021

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