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Mesoscale Discussion 1266
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   MESOSCALE DISCUSSION 1266
   NWS STORM PREDICTION CENTER NORMAN OK
   0243 PM CDT WED JUL 01 2015

   AREAS AFFECTED...PORTIONS OF MONTANA

   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

   VALID 011943Z - 012215Z

   PROBABILITY OF WATCH ISSUANCE...20 PERCENT

   SUMMARY...THE AREA IS BEING MONITORED FOR AN INCREASING RISK OF
   ISOLATED SEVERE THUNDERSTORMS THIS AFTERNOON...THOUGH LIMITED SVR
   COVERAGE IS PRESENTLY FORECAST TO PRECLUDE WW ISSUANCE.

   DISCUSSION...ISOLATED TSTMS ARE DEVELOPING INVOF THE MONTANA HI-LINE
   NWD INTO ADJACENT PARTS OF SRN CANADA...WITHIN A COMPACT ZONE OF
   DCVA PRECEDING A MID-LEVEL VORT MAX ADVANCING SEWD FROM SRN ALBERTA.
   AHEAD OF THIS ACTIVITY...THE AIR MASS CONTINUES TO DESTABILIZE
   ACROSS THE REGION OWING TO DIURNAL DIABATIC SFC HEATING...
   PARTICULARLY NEAR AND N OF A SFC TROUGH ANALYZED FROM NEAR GREAT
   FALLS TO S OF BAKER. THIS IS WHERE THE PBL IS RELATIVELY MOISTER --
   CHARACTERIZED BY SFC DEWPOINTS IN THE UPPER 50S TO LOWER 60S --
   SUPPORTING AROUND 1000-1500 J/KG OF MLCAPE. DEEPER MIXING FARTHER S
   IS SCOURING OUT LOW-LEVEL MOISTURE TO SOME EXTENT YIELDING SLIGHTLY
   LESS UPWARD BUOYANCY. ISOLATED SUPERCELLS MAY EVOLVE FROM THE
   ONGOING TSTMS...AND POTENTIALLY DEVELOP FROM TERRAIN-DRIVEN
   CIRCULATIONS. ALL OF THIS ACTIVITY WILL SPREAD SEWD INTO THE LATE
   AFTERNOON/EVENING HOURS AMIDST 30-45 KT OF EFFECTIVE BULK SHEAR.
   ISOLATED SVR HAIL/WIND MAY OCCUR WITH THIS ACTIVITY. HOWEVER...GIVEN
   THE NARROW ZONE OF ASCENT...AND LACK OF EVEN STRONGER BUOYANCY...
   CONFIDENCE IN A GREATER-COVERAGE SVR RISK IS PRESENTLY TOO LIMITED
   FOR WW ISSUANCE.

   ..COHEN/HART.. 07/01/2015


   ATTN...WFO...BYZ...GGW...TFX...

   LAT...LON   45630512 45950779 46840989 47371079 48151101 48510884
               48470628 48260477 47410411 46380414 45630512 

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Page last modified: July 01, 2015
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