MESOSCALE DISCUSSION 2048
   NWS STORM PREDICTION CENTER NORMAN OK
   0346 PM CDT WED AUG 24 2011
   
   AREAS AFFECTED...CNTRL AND NERN IL...NRN IN...SRN MI...NWRN OH
   
   CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 
   
   VALID 242046Z - 242215Z
   
   AN EXPECTED INCREASE IN TSTM COVERAGE SHOULD OCCUR THROUGH EARLY
   EVENING FROM CNTRL IL NEWD INTO SERN MI. AN ACCOMPANYING THREAT OF
   DMGG WINDS AND LARGE HAIL WILL LIKELY REQUIRE ISSUANCE OF A WW
   BETWEEN 22-00Z.
   
   AN UPPER LEVEL SPEED MAX EVIDENT ON RECENT WATER VAPOR IMAGERY IS
   CURRENTLY DIVING SEWD ACROSS SRN WI AND NRN IL...AND WILL OVERSPREAD
   A SFC COLD FRONT /ANALYZED AT 20Z FROM 15 NW GRR TO 30 SW RFD TO 25
   SW BRL/ WITH INCREASING COUPLED FORCED ASCENT EXPECTED TO SUPPORT
   CONVECTIVE INITIATION. VISIBLE IMAGERY SHOWS A BAND OF LOW-TOPPED CU
   FORMING ALONG A PRE-FRONTAL SFC TROUGH OVER CNTRL IL AND NWRN
   IN...BUT PRIMARY FOCUS FOR CONVECTION IS EXPECTED TO REMAIN ALONG
   THE COLD FRONT. THE PRE-FRONTAL AIR MASS HAS BECOME EXTREMELY
   UNSTABLE /MLCAPE VALUES 4000-4500 J/KG/ AND WEAKLY INHIBITED WITH
   RICH BOUNDARY LAYER MOISTURE IN PLACE...AND SHOULD SUPPORT EXPLOSIVE
   UPDRAFT DEVELOPMENT WITHIN THE NEXT 1-3 HRS. PRIMARY CONVECTIVE MODE
   WILL LIKELY FAVOR DISCRETE STORM STRUCTURES INITIALLY...WITH SOME
   SUPERCELLS CAPABLE OF PRODUCING LARGE HAIL AND DMGG WINDS...BUT
   ACTIVITY SHOULD GROW UPSCALE /GIVEN SIGNIFICANT PARALLEL COMPONENT
   OF EFFECTIVE SHEAR VECTOR TO THE COLD FRONT/ AND EVOLVE INTO A
   PRIMARY THREAT OF DMGG WINDS WITH EMBEDDED BOWING SEGMENTS...AND
   PERHAPS AN ISOLATED TORNADO. TRENDS WILL CONTINUE TO BE MONITORED
   FOR ISSUANCE OF A WW.
   
   ..ROGERS.. 08/24/2011
   
   
   ATTN...WFO...CLE...ILN...DTX...IWX...GRR...IND...LOT...ILX...
   LSX...DVN...
   
   LAT...LON   41498287 41008376 40468496 39868646 39628767 39458916
               39709047 40129063 40609028 41618750 42188609 43058349
               42848285 42478254 41498287