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Mesoscale Discussion 961
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MD 961 graphic

   Mesoscale Discussion 0961
   NWS Storm Prediction Center Norman OK
   0913 PM CDT Tue Jun 06 2017

   Areas affected...A small part of South Florida including portions of
   the Miami area and the FL Keys

   Concerning...Severe potential...Watch unlikely 

   Valid 070213Z - 070445Z

   Probability of Watch Issuance...5 percent

   SUMMARY...An isolated severe risk will exist across a small part of
   South Florida through the overnight hours. A low risk for isolated
   damaging wind gusts or a tornado could exist, but Watch issuance is
   very unlikely.

   DISCUSSION...A forward-propagating convective cluster has advanced
   across the central FL Peninsula and moved offshore. An outflow
   boundary, trailing southwest of the convective complex that recently
   moved off the Palm Beach to Fort Lauderdale area coast, is denoted
   by a fine line on Miami radar imagery drifting slowly southward
   across the Miami area from Coral Gables westward to Mainland Monroe
   County. This boundary may slow its southward progress or stall a
   little farther south, owing to the deep southerly flow component
   sampled by the Miami VAD wind profile while the primary cold pool
   surge spreads off the Atlantic coast.

   Additional convection regenerating off the southwest coast of FL in
   a persistent warm conveyor will spread eastward across the area into
   the overnight hours. With 30-35 kt of deep shear, continued
   semi-organized convective structures could move across the area.
   Localized wet microbursts may support isolated damaging wind 
   gusts -- aided by water-loading processes in the very moist
   environment characterized by a PW around 2.2 inches per the 00Z
   Miami sounding. Also, a low tornado risk may accompany mesovortices
   and/or transient supercell structures embedded within the convective
   clusters. This could focus around pre-existing vertical vorticity
   attendant to the outflow boundary, amid sufficient low-level shear
   and ample low-level moisture sampled by the aforementioned 
   sounding -- e.g., 17.6 g/kg mean mixing ratio -- supporting around
   125 J/kg of 0-3-km MLCAPE. Storms with strong wind gusts may also
   cross the FL Keys -- evolving from the regenerating upstream
   convection. However, across the area, the presence of (1) poor lapse
   rates, (2) the cluster-type convective mode, and (3) lack of
   stronger deep shear should prevent a more substantial severe risk
   from evolving.

   ..Cohen/Hart.. 06/07/2017

   ...Please see for graphic product...


   LAT...LON   25208138 25648092 25798072 25858041 25778016 25528016
               25068042 24588130 24578215 25208138 

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