SPC AC 060720

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0220 AM CDT Wed Sep 06 2017

   Valid 081200Z - 091200Z

   ...NO SEVERE THUNDERSTORM AREAS FORECAST...

   ...SUMMARY...
   Isolated to scattered thunderstorms are possible over many areas
   west of the Plains Friday afternoon and evening. Severe
   thunderstorms are not currently anticipated.

   ...Synopsis...
   Upper trough over the Great Lakes and Northeast at the beginning of
   the period will continue to drift northeastward as a series
   shortwaves rotate through its base. Upper ridging from the southern
   Plains into the northern Rockies will remain largely in place, 
   resulting in an omega block. As a result, developing upper low off
   the northern CA coast will move little during the period. Primary
   feature of interest will be Hurricane Irma. The center of Irma is
   expected to be off the northeastern coast of Cuba at 00Z/Saturday.
   Official and most up-to-date forecast information is available from
   the National Hurricane Center.

   ...FL Peninsula...
   The westward progress of Hurricane Irma will have a large impact on
   whether or not the FL peninsula experiences an environment conducive
   to tropical cyclone tornadoes during the period. Current guidance
   suggests the system will be too far east/southeast of the FL
   peninsula to support a tornado threat. However, updates may be
   needed in subsequent forecasts if the forecast track of the
   hurricane indicates it will be closer to the southern FL peninsula
   during the period. 

   ...Central High Plains...
   Surface lee troughing is expected sharpen across the High Plains on
   Friday with the resulting southeasterly upslope flow beneath
   northwesterly flow aloft contributing to moderate shear across the
   central High Plains. Modest low-level moisture (i.e. dewpoints in
   the low 50s) and warm mid-level temperatures are currently forecast,
   which, despite above-average surface temperatures, keeps the chances
   for daytime convective initiation low. A dynamically enhanced
   low-level jet will develop during the evening and persist overnight.
   WAA associated with this jet may support thunderstorm development
   but, as with the daytime convection, scant low-level moisture
   results in a relatively low probability for storms.

   ..Mosier.. 09/06/2017

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   NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z