MESOSCALE DISCUSSION 0857
   NWS STORM PREDICTION CENTER NORMAN OK
   0215 PM CDT SUN MAY 22 2011
   
   AREAS AFFECTED...ERN LOWER MI
   
   CONCERNING...SEVERE POTENTIAL...SEVERE THUNDERSTORM WATCH LIKELY 
   
   VALID 221915Z - 222015Z
   
   DISCRETE CELLS FORMING ALONG A LOW-LEVEL CONFLUENCE AXIS BISECTING
   LOWER MI SHOULD YIELD A THREAT FOR ISOLATED SEVERE STORMS THROUGH
   LATE AFTERNOON. THE PROBABILITY OF A WW ISSUANCE BY 20Z IS 60
   PERCENT.
   
   DISCRETE TSTMS CONTINUE TO DEVELOP SWD ALONG A N/S AXIS OF
   CONFLUENCE EVIDENT IN SURFACE/SATELLITE IMAGERY THROUGH CNTRL LOWER
   MI. ALTHOUGH THE STRONGEST ACTIVITY THUS FAR HAS REMAINED CONFINED
   ACROSS THE FAR N-CNTRL PORTION OF LOWER MI...GREATER HEATING HAS
   OCCURRED ACROSS THE THUMB INTO SERN LOWER MI. MODIFIED 18Z DTX RAOB
   WOULD SUGGEST A RELATIVELY DRY BOUNDARY LAYER COULD TEMPER A MORE
   ROBUST SEVERE THREAT. NEVERTHELESS...HIGHER SURFACE DEW POINTS IN
   THE MIDDLE 60S ARE EVIDENT ALONG THE CONFLUENCE AXIS IN S-CNTRL
   LOWER MI RESULTING IN A MODERATELY UNSTABLE AIR MASS WITH MLCAPE
   NEAR 2000 J/KG. WITH EFFECTIVE SHEAR OF 30 TO 40 KT FAVORING
   SUPERCELL STRUCTURES...SEVERE HAIL WILL BE THE PRIMARY THREAT ALONG
   WITH LOCALIZED DAMAGING WINDS AND PERHAPS A BRIEF TORNADO.
   
   ..GRAMS.. 05/22/2011
   
   
   ATTN...WFO...CLE...DTX...APX...IWX...GRR...
   
   LAT...LON   41538504 44108452 45178408 45398383 45278344 44018258
               43008249 41848306 41448338 41338398 41538504