SPC AC 271956

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0256 PM CDT Tue Sep 27 2022

   Valid 272000Z - 281200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS CENTRAL AND
   SOUTHERN FLORIDA...

   ...SUMMARY...
   Tornadoes are possible across the Florida Keys and south Florida
   this afternoon, and may spread into parts of central Florida
   overnight with Hurricane Ian.

   ...Discussion...
   Aside from adjustments in the thunder area -- particularly across
   the Texas South Plains area and eastern Lower Michigan -- the
   forecast areas and reasoning laid out in prior outlooks continue to
   reflect the evolving scenario.

   In the past hour or so, several rotating cells have evolved across
   South Florida, within one of the more prominent convective bands
   rotating around Ian's center, contributing to the
   anticipated/gradual increase in tornado potential.  The potential
   should expand northward with time, as Ian advances
   north-northeastward.

   ..Goss.. 09/27/2022

   .PREV DISCUSSION... /ISSUED 1126 AM CDT Tue Sep 27 2022/

   ...South FL and the Keys through tonight...
   Major Hurricane Ian will move northward or north-northeastward
   through tonight across the extreme southeast Gulf of Mexico, as rain
   bands east-through-northeast of the center continue to overspread
   south FL and the Keys.  Some expansion of the stronger wind field,
   and resultant stronger vertical shear (effective SRH of 200-400
   m2/s2), will occur through tonight as Ian continues to deepen (see
   latest NHC advisories for additional information).  Widespread rain
   across south FL has held surface temperatures in the mid 70s through
   the morning with minimal surface-based buoyancy.  However, some
   cloud breaks and modest surface heating is underway across the Keys,
   and should develop slowly inland from the southeast FL coast through
   the afternoon.  Likewise, slightly higher boundary-layer dewpoints
   (>76 F) will spread inland, with sufficient destabilization to
   support supercells moving inland.  Thus, the threat for tornadoes is
   expected to gradually increase from south-to-north later this
   afternoon/evening, and persist into the overnight hours.  Please see
   SPC MD 1833 for additional details.

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