MESOSCALE DISCUSSION 1591
   NWS STORM PREDICTION CENTER NORMAN OK
   0100 PM CDT TUE JUL 12 2011
   
   AREAS AFFECTED...NORTHEAST MO/FAR SOUTHEAST IA TO CENTRAL/SOUTHERN
   IL AND SOUTHWEST INDIANA/FAR WESTERN KY
   
   CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 
   
   VALID 121800Z - 122000Z
   
   POTENTIAL FOR LARGE HAIL AND ESPECIALLY DAMAGING WINDS ARE EXPECTED
   TO INCREASE THROUGH THE AFTERNOON FROM SOUTHEAST IA/NORTHERN MO INTO
   CENTRAL/SOUTHERN PORTIONS IL AND EVENTUALLY INDIANA/WESTERN KY. IT
   DOES APPEAR LIKELY THAT A SEVERE TSTM WATCH WILL BE NEEDED FOR
   PORTIONS OF THE REGION BY MID AFTERNOON.
   
   A CONVECTIVELY-AIDED/INDUCED IMPULSE IS EVIDENT IN SATELLITE IMAGERY
   OVER IA EARLY THIS AFTERNOON...WITH SEVERAL SCATTERED POCKETS OF
   TSTMS ACROSS FAR SOUTHEAST IA AND NORTHEAST MO...WHICH ARE FOCUSED
   NEAR/NORTH OF A SOUTHWARD SHIFTING WEST-EAST ORIENTED FRONTAL
   BOUNDARY/INSTABILITY GRADIENT. LIFT ASSOCIATED WITH THE
   AFOREMENTIONED MID-LEVEL IMPULSE IS EXPECTED TO SUPPORT INCREASING
   SURFACE BASED DEEP CONVECTION THROUGH MID/LATE AFTERNOON ACROSS
   PORTIONS OF NORTHEAST/EAST-CENTRAL MO INTO MUCH OF DOWNSTATE IL.
   SUCH A SCENARIO IS WELL SUPPORTED BY GUIDANCE SUCH AS THE 12Z
   WRF-NMM AND LATEST EXPERIMENTAL HRRR. WITHIN THE AFOREMENTIONED
   CORRIDOR...RELATIVELY CLOUD-FREE SKIES ARE CONTRIBUTING TO
   AGGRESSIVE DESTABILIZATION/CINH EROSION WITHIN A VERY MOIST AIRMASS
   WITH SURFACE DEWPOINTS RANGING FROM THE UPPER 60S TO MIDDLE 70S F.
   THIS IS RESULTING IN MLCAPE ON THE ORDER OF 2000-4000 J/KG...HIGHEST
   ACROSS NORTHEAST MO EAST-SOUTHEASTWARD INTO DOWNSTATE PORTIONS OF
   IL/INDIANA. MODEST/NEARLY UNIDIRECTIONAL WESTERLY FLOW COUPLED WITH
   THE AFOREMENTIONED DEGREE OF INSTABILITY WILL SUPPORT THE
   DEVELOPMENT/ORGANIZATION OF MULTICELLULAR CLUSTERS/SOME SUPERCELLS
   CAPABLE OF DAMAGING WINDS/LARGE HAIL.
   
   ..GUYER.. 07/12/2011
   
   
   ATTN...WFO...IND...PAH...ILX...LSX...DVN...EAX...
   
   LAT...LON   39879307 40939124 40528924 39648750 38198732 37498853
               38069068 39879307