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Mesoscale Discussion 1446
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   MESOSCALE DISCUSSION 1446
   NWS STORM PREDICTION CENTER NORMAN OK
   0110 PM CDT FRI JUL 17 2015

   AREAS AFFECTED...PORTIONS OF EASTERN ND...NORTHEAST SD...WESTERN AND
   CENTRAL MN

   CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

   VALID 171810Z - 172015Z

   PROBABILITY OF WATCH ISSUANCE...80 PERCENT

   SUMMARY...SCATTERED THUNDERSTORM DEVELOPMENT IS EXPECTED OVER THE
   NEXT FEW HOURS AHEAD OF A COLD FRONT FROM SOUTHEAST ND/NORTHEAST SD
   INTO WESTERN MN. LARGE HAIL AND STRONG WINDS WILL BE THE MAIN THREAT
   WITH THESE STORMS...BUT A TORNADO ALSO WILL BE POSSIBLE...ESPECIALLY
   ACROSS NORTHEAST SD. A WATCH WILL LIKELY BE NEEDED WITHIN THE NEXT
   HOUR OR TWO.

   DISCUSSION...STRONG HEATING TO THE SOUTH/EAST OF A COLD FRONT ACROSS
   THE EASTERN DAKOTAS INTO MN HAS LEAD TO A QUICKLY ERODING CAP IN A
   WEAK TO MODERATELY UNSTABLE ENVIRONMENT. VISIBLE SATELLITE IMAGERY
   HAS SHOWS AN INCREASE IN CUMULUS DEVELOPMENT FROM NORTHEAST SD INTO
   WEST-CENTRAL MN OVER THE LAST HOUR. WITH ADDITIONAL HEATING AND THE
   APPROACH OF A SHORTWAVE IMPULSE TO THE WEST...ADDITIONAL
   THUNDERSTORM DEVELOPMENT IS EXPECTED BETWEEN 19-21Z. EFFECTIVE SHEAR
   GREATER THAN 35 KT AND VERTICALLY VEERING WIND PROFILES WILL
   INITIALLY FAVOR SEMI-DISCRETE CELLS WITH SUPERCELL CHARACTERISTICS.
   STEEP LAPSE RATES AND COOLING TEMPERATURES ALOFT WILL AID IN LARGE
   HAIL PRODUCTION. FURTHERMORE...A DEEPLY MIXED BOUNDARY LAYER WITH
   INVERTED-V TYPE SOUNDINGS MAY ENHANCE THE WIND THREAT...ESPECIALLY
   GIVEN PW VALUES AOA 1.50 INCHES. THE TORNADO THREAT...WHILE LESSER
   THAN THE WIND AND HAIL THREAT...WILL NOT BE ZERO. THE GREATEST
   TORNADO THREAT WILL BE ENHANCED NEAR A WEAK SURFACE LOW...CENTERED
   OVER NORTHEAST SD AS OF 18Z...WHERE LOW LEVEL CONVERGENCE AND BACKED
   SURFACE WINDS WILL BE MAXIMIZED. AS STORMS TRACK GENERALLY EASTWARD
   TOWARD MN...SOME UPSCALE GROWTH INTO BOWING LINE SEGMENTS IS
   POSSIBLE.  A WATCH WILL LIKELY BE NEEDED BY 20Z.

   ..LEITMAN/CORFIDI.. 07/17/2015


   ATTN...WFO...DLH...MPX...FGF...FSD...ABR...BIS...

   LAT...LON   47879812 48119738 47929661 47609569 46949510 46209461
               45589444 44989454 44289471 44089539 43969614 43929728
               44069842 44269932 44670007 45080040 45739996 46629928
               47879812 

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Page last modified: July 17, 2015
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