Mesoscale Discussion 0371
   NWS Storm Prediction Center Norman OK
   0113 AM CDT Mon Apr 12 2021

   Areas affected...Portions of the Florida Keys.

   Concerning...Severe potential...Watch unlikely 

   Valid 120613Z - 120845Z

   Probability of Watch Issuance...5 percent

   SUMMARY...Isolated severe hail is possible from convection moving
   southeastward across mainly the lower/middle Keys for a few more
   hours.  A watch is unlikely.

   DISCUSSION...Surface mesoanalysis depicts an outflow boundary --
   produced by the earlier/severe peninsular MCS -- progressing
   southward over the area from the central Bahamas to the Cuban
   coastline near MUVR/Varadero, then northwestward across the Straits
   of Florida southwest of EYW.  The western part of the boundary,
   northwest of Varadero, is decelerating and may stall and retreat
   northward the next few hours.  

   VWP from BYX radar indicates the cold pool is shallow, with
   southerlies at 850 mb supplying richly moist inflow to elevated
   convection north of the boundary.  That includes a supercell with
   occasional MESH indicators of severe hail, located about 40 NNE of
   EYW at 06Z, and moving southeastward generally toward the
   Marathon/Seven Mile Bridge area.  Other isolated strong-severe
   thunderstorms also may form in this regime, where modified RAOBs and
   forecast soundings suggest around 500-1000 MUCAPE atop the stable
   boundary layer.  Favorable vertical shear is apparent atop the cold
   pool as well, in the form of veering with height and 50-60-kt
   effective-shear magnitudes.  The cold pool should become shallower
   with time -- especially around the lower Keys -- indicating the
   potential for localized downdraft gusts approaching severe limits to
   penetrate to the surface as well.

   ..Edwards.. 04/12/2021

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

   ATTN...WFO...KEY...

   LAT...LON   24888070 24668100 24568159 24518212 24618294 24698291
               24598211 24618180 24718169 24718158 24848149 24798125
               24738118 24818091 24888070