MESOSCALE DISCUSSION 0778
   NWS STORM PREDICTION CENTER NORMAN OK
   0440 PM CDT FRI MAY 13 2011
   
   AREAS AFFECTED...FAR EASTERN MO AND MUCH OF DOWNSTATE IL
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 132140Z - 132315Z
   
   BOUTS OF MARGINALLY SEVERE HAIL /AND PERHAPS A BRIEF TORNADO/ WILL
   BE POSSIBLE THROUGH AROUND SUNSET FROM FAR EASTERN MO INTO MUCH OF
   DOWNSTATE IL.
   
   WATER VAPOR IMAGERY REFLECTS A CLOSED/NEARLY STACKED CYCLONE
   SHIFTING EAST-SOUTHEASTWARD OVER SOUTHERN MO LATE THIS
   AFTERNOON...WITH A SURFACE FRONTAL BOUNDARY ANALYZED FROM FAR
   EASTERN MO NORTHEASTWARD INTO NORTHERN IL. AIDED BY STEEP LAPSE
   RATES ALOFT ATTENDANT TO THE UPPER LOW...THE FRONTAL ADJACENT WARM
   SECTOR IS RELATIVELY UNSTABLE WITH MLCAPE ON THE ORDER OF 500-1000
   J/KG. WHILE VERTICAL SHEAR IS RATHER WEAK PER REGIONAL WSR-88D VWP
   DATA...PULSE-TYPE HAIL TO NEAR SEVERE LEVELS MAY BE POSSIBLE.
   ADDITIONALLY...GIVEN THE DEGREE OF RESIDUAL LOW LEVEL LAPSE
   RATES/CAPE IN VICINITY OF THE AFOREMENTIONED SURFACE
   BOUNDARY...FUNNELS/PERHAPS A BRIEF TORNADO CANNOT BE RULED OUT
   WITHIN A CORRIDOR FROM NEAR/NORTH OF THE ST LOUIS AREA NORTHEASTWARD
   INTO NORTH-CENTRAL IL UNTIL AROUND SUNSET.
   
   ..GUYER.. 05/13/2011
   
   
   ATTN...WFO...PAH...LOT...ILX...LSX...DVN...
   
   LAT...LON   39169124 40449063 41698905 40928810 39788856 38428880
               37738840 37648970 39169124