MESOSCALE DISCUSSION 0734
   NWS STORM PREDICTION CENTER NORMAN OK
   0155 PM CDT WED MAY 06 2009
   
   AREAS AFFECTED...PARTS OF SWRN MN / NWRN IA
   
   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 
   
   VALID 061855Z - 062000Z
   
   STORM COVERAGE/INTENSITY WILL LIKELY INCREASE THIS AFTERNOON ALONG
   PREFRONTAL WIND-SHIFT OVER PARTS OF SWRN MN AND NWRN IA...POSING
   MAINLY AN ISOLD LARGE HAIL THREAT.
   
   LATEST SATELLITE IMAGERY SHOWS A SHORTWAVE TROUGH AND ZONE OF
   MID-LEVEL MOISTENING/IMPLIED ASCENT MOVING EWD OVER THE ERN DAKOTAS
   AND BEGINNING TO OVERSPREAD WRN MN INTO NWRN IA.  SUSTAINED LOW
   LEVEL CONVERGENCE ALONG PREFRONTAL WIND-SHIFT /RECENTLY ANALYZED
   FROM 30 MI WNW RWF TO NEAR SUX/ AND STRONG DIABATIC HEATING
   IMMEDIATELY AHEAD OF APPROACHING BOUNDARY HAVE LED TO DEVELOPING
   TSTMS.
   
   RATHER STEEP H85-H5 LAPSE RATES /7-8 DEG C PER KM/ WERE OBSERVED ON
   MPX/OAX 12Z RAOBS AND ARE CONTRIBUTING TO A NARROW CORRIDOR OF
   MODEST CONVECTIVE INSTABILITY /500-1000 MLCAPE/.  DESPITE WEAK DEEP
   LAYER SHEAR LEADING TO MAINLY PULSE-LIKE UPDRAFTS...LARGE SCALE
   FORCING FOR ASCENT WILL AID IN MAINTAINING A SEMI-ORGANIZED BROKEN
   LINE AS TSTMS MOVE EWD OVER THE DISCUSSION AREA...WITH LARGE HAIL
   THE PRIMARY THREAT.  NRN AND ERN EXTENT OF MOST PROBABLE SEVERE
   POTENTIAL IS BOUNDED BY DRIER AIR /DEWPOINTS IN THE 30S-40S F ACROSS
   S-CNTRL MN/ TO THE N AND MARGINALIZED AIRMASS FOR THE TIME BEING
   FURTHER E OVER S-CNTRL MN EXTENDING INTO N-CNTRL IA DUE TO A COLD
   POOL FROM PRIOR CONVECTION.
   
   ..SMITH.. 05/06/2009
   
   
   ATTN...WFO...MPX...DMX...FSD...OAX...
   
   LAT...LON   41729611 42519643 43439640 44369571 44829500 44779430
               44429418 43699468 42519480 41989493 41859505 41669540
               41729611