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Mesoscale Discussion 1680
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   MESOSCALE DISCUSSION 1680
   NWS STORM PREDICTION CENTER NORMAN OK
   0504 PM CDT THU SEP 04 2014

   AREAS AFFECTED...SE MN...NE IA...CNTRL AND SRN WI

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

   VALID 042204Z - 042330Z

   PROBABILITY OF WATCH ISSUANCE...40 PERCENT

   SUMMARY...AN ISOLATED SEVERE THREAT MAY DEVELOP LATE THIS AFTERNOON
   INTO EARLY THIS EVENING FROM SE MN AND NE IA EWD ACROSS MUCH OF SRN
   AND CNTRL WI. WW ISSUANCE MAY BE NEEDED ACROSS THE REGION.

   DISCUSSION...THE LATEST SFC ANALYSIS SHOWS A COLD FRONT MOVING EWD
   ACROSS ERN AND SRN MN WITH SW TO SLY FLOW LOCATED ACROSS MUCH OF THE
   UPPER MS VALLEY. SFC WINDS WERE LOCALLY BACKED TO THE EAST AND
   SOUTHEAST JUST AHEAD OF THE ACTIVITY IN WCNTRL WI. IN ADDITION...A
   VERY MOIST AIRMASS WAS IN PLACE TO THE EAST OF THE COLD FRONT WITH
   SFC DEWPOINTS IN THE MID TO UPPER 70S F ACROSS ERN IA...SE MN AND SW
   WI. SFC TEMPS ARE MOSTLY IN THE 80S F WHICH HAS RESULTING IN STRONG
   DESTABILIZATION WITH MLCAPE ESTIMATED IN THE 2500 TO 3500 J/KG
   RANGE. THIS COMBINED WITH 40 TO 50 KT OF DEEP-LAYER SHEAR EVIDENT ON
   THE LACROSSE WI WSR-88D VWP SHOULD BE SUPPORTIVE OF AT LEAST
   ISOLATED SEVERE THUNDERSTORM DEVELOPMENT EARLY THIS EVENING.
   THUNDERSTORMS MAY INCREASE IN COVERAGE AS A SUBTLE SHORTWAVE TROUGH
   SEEN ON WATER VAPOR IMAGERY...MOVES EWD TOWARD THE MS RIVER VALLEY
   OVER THE NEXT FEW HOURS. THE HIGH MOISTURE CONTENT IN THE BOUNDARY
   LAYER MAY BE SUPPORTIVE OF WET DOWNBURSTS. LOW-LEVEL SHEAR APPEARS
   STRONG ENOUGH FOR AN ISOLATED TORNADO THREAT AS WELL. HAIL MAY ALSO
   OCCUR DUE TO THE STRONG INSTABILITY AND STEEP MID-LEVEL LAPSE RATES.

   ..BROYLES/MEAD.. 09/04/2014


   ATTN...WFO...GRB...MKX...ARX...MPX...

   LAT...LON   42958798 42748945 42739069 42909141 43739205 44769158
               45049043 45088860 44558756 42958798 

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Page last modified: September 04, 2014
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