SPC AC 190723

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0123 AM CST Sun Dec 19 2021

   Valid 211200Z - 221200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
   FLORIDA PENINSULA...

   ...SUMMARY...
   A few strong to severe thunderstorms are possible across the Florida
   Peninsula on Tuesday morning/afternoon.

   ...Synopsis...
   A shortwave trough will move from the central Gulf Coast Tuesday
   morning to the western Atlantic by early Wednesday. A deepening
   surface cyclone will accompany this trough eastward with a warm
   front moving north along the Peninsula through the morning hours. 

   ...Florida Peninsula...
   Low-level thermal and moisture advection will be occurring Tuesday
   ahead of the surface low as it approaches the Florida coast. This
   will lead to at least some destabilization and potential for strong
   thunderstorms as the shear profile strengthens. However, there is
   considerable model disagreement regarding the strength of the
   upper-level trough and thus the strength/location of the surface
   low. This will affect the location, intensity, and timing of any
   severe storm threat. The ECMWF has been the most consistent over the
   past several runs and thus, more weight is being given to the
   stronger ECMWF solution. This solution has greater instability and
   shear and could pose a tornado threat along and just south of the
   warm front where low-level flow would be more backed, increasing
   low-level SRH. 

   In addition, mid-level lapse rates will be quite weak across the
   Peninsula which casts doubt on the strength of any storms which do
   form with this surface low. It appears dewpoints approaching 70F may
   be necessary for a thermodynamic profile favorable for more robust
   updraft development and a greater severe weather threat. Given the
   frontal passage on Sunday/Sunday night, this will require
   significant moisture return on Monday night and Tuesday morning
   which the ECMWF currently shows, but which is not as apparent from
   other guidance. 

   Therefore, there is sufficient risk for severe storms on Tuesday
   morning/afternoon to justify a marginal risk, but uncertainty in the
   synoptic setup remains higher than may typically be expected for a
   Day 3 forecast and thus forecast confidence is lower than normal.

   ..Bentley.. 12/19/2021

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