Mesoscale Discussion 1861
   NWS Storm Prediction Center Norman OK
   0255 PM CST Sun Dec 20 2020

   Areas affected...northwest Florida Peninsula and adjacent coastal
   waters

   Concerning...Severe potential...Watch unlikely 

   Valid 202055Z - 202300Z

   Probability of Watch Issuance...5 percent

   SUMMARY...Thunderstorms are increasing in coverage and intensity
   across the northeast Gulf of Mexico. These thunderstorms will
   continue to develop and move east through the afternoon and evening
   hours. The strongest thunderstorms will pose a brief tornado/gusty
   wind threat. A watch is currently not expected.

   DISCUSSION...Recent satellite and radar imagery, coupled with an
   increase in lightning activity, indicate an increase in coverage and
   intensity of convection across the northeast Gulf of Mexico. These
   thunderstorms are developing along a low-level confluence zone 
   within a broad warm-air advection regime ahead of a surface low and
   cold front pushing east across the Gulf.

   Modest destabilization is occurring along and ahead of this new
   convection owing largely to an increase in low-level moisture and
   corresponding increase in theta-e. This should continue into the
   evening supporting thunderstorm development. Given favorable
   deep-layer shear at or above 40 knots and 0-3km storm-relative
   helicity over 200 m2/s2 based on Tampa Bay VAD, transient
   supercell-like structures and a brief tornado/waterspout or gusty
   winds may be observed with some of the strong thunderstorm cores. 

   The overall threat should be limited spatially primarily to the Gulf
   of Mexico with limited inland penetration of the overall threat
   owing to the cooler, more stable airmass over the Florida Peninsula.
   As such, a watch is currently not expected this evening.

   ..Marsh/Guyer.. 12/20/2020

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...TBW...JAX...TAE...

   LAT...LON   26718435 28358410 29038384 29388319 29008230 28288223
               27398239 26998250 26698325 26578370 26718435