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Mesoscale Discussion 1550
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   MESOSCALE DISCUSSION 1550
   NWS STORM PREDICTION CENTER NORMAN OK
   1240 PM CDT MON JUL 27 2015

   AREAS AFFECTED...CENTRAL AND SOUTHERN IA

   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

   VALID 271740Z - 272045Z

   PROBABILITY OF WATCH ISSUANCE...20 PERCENT

   SUMMARY...A RELATIVELY COMPACT MCS WILL ADVANCE TO THE EAST ACROSS
   CENTRAL AND PORTIONS OF SOUTHERN IA THIS AFTERNOON.  ALTHOUGH MOST
   OF THE WIND GUSTS ASSOCIATED WITH THIS ACTIVITY SHOULD REMAIN
   SUB-SEVERE...LOCALLY STRONG WIND GUSTS /POTENTIALLY REACHING OR
   EXCEEDING 50 KT/ CANNOT BE RULED OUT.

   DISCUSSION...DMX RADAR TRENDS AND PERSISTENT CLOUD-TOP COOLING PER
   IR SATELLITE IMAGERY INDICATED A FORWARD-PROPAGATING LINEAR MCS
   ADVANCING EASTWARD ACROSS CENTRAL IA.  AS THE STORMS MOVED THROUGH
   THE COUNTIES OF BOONE...DALLAS...AND MADISON THE ATTENDANT OUTFLOW
   BOUNDARY HAD MOVED AHEAD OF THE STRONGER BAND OF STORMS INDICATING
   ANY STRONGER WIND GUSTS ATTENDANT TO THIS MCS MAY NOT BE REACHING
   THE SURFACE.  HOWEVER...IF THE STRONGER ACTIVITY CAN OVERTAKE THE
   OUTFLOW BOUNDARY...AS MAY BE ONGOING IN NORTHEAST DALLAS COUNTY AND
   PORTIONS OF WESTERN POLK COUNTY...THEN 55+ KT WLY WINDS OBSERVED
   AROUND 500 FEET AGL IN THAT PORTION OF DALLAS COUNTY WILL HAVE A
   GREATER POTENTIAL TO REACH THE SURFACE.

   GIVEN THE ORGANIZATION OF THIS MCS WITH AN ACCOMPANYING COLD POOL
   AND REAR-INFLOW JET OF 40-45 KT AT 1-2 KM AGL PER DMX RADAR 
   COMBINED WITH A SURFACE-BASED INFLOW REGIME THAT HAS MODERATELY
   STRONG INSTABILITY...THIS COMPLEX IS EXPECTED TO PERSIST THROUGH THE
   AFTERNOON...TRACKING TO EAST ALONG AN INSTABILITY GRADIENT.  AN
   EVENTUAL SOUTHEASTWARD TURN MAY OCCUR BETWEEN 19-20Z AS THE SOUTHERN
   FLANK REACHES POWESHIEK AND MAHASKA COUNTIES WHERE THE INSTABILITY
   GRADIENT IS ORIENTED NW-SE.  ALTHOUGH SHORT-TERM MODELS HAVE HAD
   DIFFICULTY FORECASTING THIS COMPLEX...THE HRRR /THOUGH SLOW WITH ITS
   DEVELOPMENT AND PLACEMENT/ SUGGESTS THIS STORM COMPLEX SHOULD
   PERSIST THROUGH THE AFTERNOON WITH AN EVENTUAL SEWD MOVEMENT.  ELY
   SURFACE WINDS WILL CONTINUE TO ENHANCE DEEP SHEAR FOR STORM
   ORGANIZATION...WHILE FORCING FOR ASCENT ATTENDANT TO A WEAK
   EWD-MOVING MIDLEVEL IMPULSE AIDS IN SUSTAINING TSTM DEVELOPMENT
   WITHIN THIS MCS.

   ..PETERS/GOSS.. 07/27/2015


   ATTN...WFO...DVN...DMX...

   LAT...LON   41909250 41849204 41549168 40999158 40909197 40899242
               41129292 41339404 41629419 41869415 42029404 41909250 

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Page last modified: July 27, 2015
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