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Mesoscale Discussion 667
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   MESOSCALE DISCUSSION 0667
   NWS STORM PREDICTION CENTER NORMAN OK
   0354 PM CDT SAT MAY 21 2016

   AREAS AFFECTED...ERN MT...ERN WY

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

   VALID 212054Z - 212300Z

   PROBABILITY OF WATCH ISSUANCE...40 PERCENT

   SUMMARY...ISOLATED SEVERE THUNDERSTORMS ARE POSSIBLE LATER THIS
   AFTERNOON/EVENING...WITH A PRIMARY THREAT OF LARGE HAIL AND DAMAGING
   WINDS.

   DISCUSSION...CONVECTION HAS THUS FAR BEEN SLOW TO DEVELOP ACROSS
   PORTIONS OF ERN WY/MT...WITH CLOUDINESS LIMITING THE AMOUNT OF
   HEATING THUS FAR. HOWEVER...SOME BREAKS HAVE RECENTLY BEEN NOTED
   ACROSS SERN MT INTO ERN WY...WITH TEMPERATURES RISING INTO THE
   MID/UPPER 70S. STEEP MIDLEVEL LAPSE RATES ARE SUPPORTING SBCAPE OF
   1500-2000 J/KG ACROSS THE AREA...WHILE MODERATE MIDLEVEL FLOW IS
   RESULTING IN EFFECTIVE SHEAR OF 40-50 KTS. THESE PARAMETERS WOULD
   SUPPORT A RISK OF SUPERCELLS IF DEEP CONVECTION CAN INITIATE. THERE
   IS SOME VARIANCE IN RECENT GUIDANCE REGARDING TIMING AND COVERAGE OF
   INITIATION...BUT MOST GUIDANCE SUGGESTS AT LEAST ISOLATED
   DEVELOPMENT BY 22-00Z. LARGE HAIL WILL BE POSSIBLE GIVEN MODERATE
   INSTABILITY AND STEEP MIDLEVEL LAPSE RATES...WHILE ISOLATED DAMAGING
   WINDS WILL ALSO BE POSSIBLE...ESPECIALLY IN AREAS THAT EXPERIENCE
   GREATER HEATING/MIXING OF THE BOUNDARY LAYER. WW ISSUANCE IS
   POSSIBLE SOMETIME IN THE NEXT 1-2 HRS IF IT APPEARS THAT INITIATION
   IS IMMINENT AND COVERAGE WARRANTS.

   ..DEAN/HART.. 05/21/2016


   ATTN...WFO...BIS...UNR...CYS...BYZ...GGW...

   LAT...LON   41240565 43020584 45150581 47020587 47930557 47970445
               46030403 44130408 41450402 41150435 41160519 41240565 

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Page last modified: May 21, 2016
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