MESOSCALE DISCUSSION 1040
   NWS STORM PREDICTION CENTER NORMAN OK
   1259 PM CDT TUE MAY 31 2011
   
   AREAS AFFECTED...MID MS VLY INTO IND AND SRN LWR MI
   
   CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 
   
   VALID 311759Z - 312030Z
   
   COLD FRONT ASSOCIATED WITH SE MB UPR LOW ATTM EXTENDS FROM FAR ERN
   IA SSW INTO CNTRL MO.  THE FRONT SHOULD CONTINUE STEADILY E INTO WRN
   IL AND ERN MO THROUGH THE AFTN.  AHEAD OF THE FRONT...REMNANTS OF
   OVERNIGHT MCS IN NEB AND THE DAKOTAS...IN THE FORM OF SHOWERS AND A
   FEW TSTMS...ARE NOW OVER N CNTRL AND W CNTRL IL.  THIS ACTIVITY HAS
   OFFSET SFC HEATING/MAINTAINED SIZABLE SFC-BASED CINH OVER THE NW
   HALF OF IL.  AT THE SAME TIME...THE ASSOCIATED CLOUDS HAVE SERVED TO
   MINIMIZE DEEP MIXING OVER THE REGION...WHILE DEEPER MIXING HAS
   OCCURRED E OF THE CLOUDS INTO PARTS OF IND/LWR MI.  THIS HAS
   RESULTED IN AN AREA OF VEERED LOW LVL FLOW/DECREASED LOW LVL
   CONFLUENCE FROM ERN IL INTO NRN IND.
   
   WATER VAPOR IMAGERY ATTM SHOWS A POTENT SHORTWAVE IMPULSE NOW
   EXTENDING FROM N CNTRL IA NNW INTO NW MN.  THIS FEATURE SHOULD
   CONTINUE PIVOTING NE TOWARD THE UPR GRT LKS THROUGH THE REMAINDER OF
   THE DAY...WITH WEAK SHORTWAVE RIDGING LIKELY TO OCCUR IN ITS WAKE
   FROM CNTRL IL WSWWD INTO MO. 
   
   AFOREMENTIONED PRESENCE OF CLOUDS...THE SOMEWHAT WEAKENED/DISRUPTED
   LOW LVL CONVERGENCE FIELD...AND THE DEPARTURE OF STRONGER FORCING
   FOR ASCENT...CAST SOME UNCERTAINTIES AS TO THE DETAILS OF STORM
   DEVELOPMENT/EVOLUTION FROM MO/IL INTO IND/SRN LWR MI LATER TODAY. 
   NEVERTHELESS...AMPLE MOISTURE AND DEEP SHEAR WILL REMAIN IN PLACE TO
   SUPPORT STRONG/SUSTAINED UPDRAFTS ALONG AND AHEAD OF THE COLD FRONT.
   IN ADDITION...HEATING...WHILE MUTED ATTM...SHOULD CONTINUE TO
   INCREASE AS MCS CLOUDS FURTHER DISSIPATE.  GIVEN THIS SETUP...AND
   THE POTENTIAL FOR A FEW STORMS TO FORM IN MORE STRONGLY
   HEATING/CONFLUENT AREA ALONG LAKE BREEZE BOUNDARY IN SW LWR MI...IT
   APPEARS THAT A SVR TSTM WATCH WILL BE NEEDED FOR AT LEAST PARTS OF
   THE REGION INCLUDING THE CHICAGO...MILWAUKEE...DETROIT...AND PERHAPS
   ST LOUIS METRO AREAS BY MID AFTN.
   
   ..CORFIDI.. 05/31/2011
   
   
   ATTN...WFO...DTX...IWX...GRR...IND...LOT...ILX...MKX...LSX...
   DVN...
   
   LAT...LON   39248926 39029015 38949121 39649175 41079043 42628922
               42968761 42678374 41938383 40278679 39248926