Mesoscale Discussion 0069
   NWS Storm Prediction Center Norman OK
   0613 PM CST Fri Jan 31 2020

   Areas affected...FL Keys and South FL

   Concerning...Severe potential...Watch possible 

   Valid 010013Z - 010115Z

   Probability of Watch Issuance...60 percent

   SUMMARY...The risk for strong to locally severe thunderstorms
   capable of damaging gusts will likely move from the Dry Tortugas and
   the Lower Keys to eventually the Upper Keys and Monroe/Miami-Dade
   counties later tonight.

   DISCUSSION...Radar mosaic as of 7pm EST shows a small-scale bow 10
   mi wnw of the Dry Tortugas moving east around 35 kt.  Surface
   analysis this evening shows a maritime/unstable airmass across the
   FL Keys with temperatures in the upper 70s degrees F and dewpoints
   in the lower 70s.  Farther north in Miami-Dade county, slightly
   cooler/drier conditions are currently observed with dewpoints in the
   middle 60s.  The 7pm EST observed sounding from KEY shows a
   moderately unstable airmass (1400 J/kg MLCAPE) with a wind profile
   more than supportive of organized storm structures.  The MFL
   observed sounding was noticeably less unstable with only 200 J/kg
   MLCAPE.  

   Forecast soundings by mid evening show low-level moisture increasing
   across extreme South FL with dewpoints rising into the upper 60s (14
   g/kg lowest 100mb mean mixing ratio) but with weak low- to mid-level
   lapse rates.  Low-level flow (surface-2km AGL) however is forecast
   to remain relatively weak (10-20 kt range).  Nonetheless, above 2km,
   flow gradually veers and strengthens with height supportive of
   organized storms and around 45 kt effective shear.  

   Current forecast thinking is a risk for damaging winds may focus on
   the low-level moisture gradient as it slowly moves from the Upper
   Keys into parts of Monroe/Miami-Dade counties.  Although a brief
   tornado cannot be ruled out given the moist low-level profile, it
   appears the wind-damage threat is the primary concern this evening.

   ..Smith/Guyer.. 02/01/2020

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

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

   LAT...LON   25907988 25298157 25018318 24188332 24228136 24718022
               25447976 25907988