MESOSCALE DISCUSSION 0564
   NWS STORM PREDICTION CENTER NORMAN OK
   0155 PM CDT SAT APR 25 2009
   
   AREAS AFFECTED...CENTRAL AND SOUTHERN LOWER MI...NORTHERN IND AND
   EXTREME NORTHEAST IL
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 251855Z - 252030Z
   
   VALID PORTIONS OF SEVERE THUNDERSTORM WATCH 181 ACROSS PORTIONS OF
   LOWER MI AND ADJACENT LAKE HURON HAS AN EXPIRATION TIME OF 20Z.  IT
   IS POSSIBLE THAT SOME OF IT WILL NEED TO BE EXTENDED AND/OR
   REISSUED...MAYBE EVEN INTO PARTS OF NORTHERN IND AND EXTREME
   NORTHEAST IL.  COORDINATION CALLS WILL BE MADE TO AFFECTED WFO/S
   SHORTLY.
   
   LEADING BOW ECHO THAT PRODUCED CONSIDERABLE DAMAGING WINDS ACROSS
   SOUTH-CENTRAL AND SOUTHEAST LOWER MI WILL CONTINUE EAST INTO
   SOUTHWEST ONTARIO.  IN ITS WAKE...PARTS OF THE SOUTHERN LOWER MI
   BOUNDARY LAYER APPEARS TO HAVE STABILIZED...THOUGH POCKETS OF
   SURFACE-BASED INSTABILITY REMAIN WHERE CONVECTIVE OVERTURNING DID
   NOT OCCUR.  TSTMS CONTINUE TO FORM...WHETHER SURFACE BASED OR
   SLIGHTLY ELEVATED...AS SOUTHWESTERLY FLOW CONTINUES TO MAINTAIN BOTH
   AN ELEVATED MIXED LAYER PLUME AND PERSISTENT LOW-LEVEL MOISTURE FEED
   FROM THE MID-MS VALLEY.  THUS...WAVES OF TSTMS ARE EXPECTED TO
   DEVELOP OVER MILWAUKEE/CHICAGOLAND AND MOVE EAST-NORTHEAST INTO
   CENTRAL/SOUTHERN LOWER MI THROUGH THE AFTERNOON.  STORMS MAY TEND TO
   BACKBUILD FARTHER SOUTH WITH TIME AS THE LOW-LEVEL CONVERGENCE ALONG
   OUTFLOW BOUNDARIES INCREASES COINCIDENT WITH STEEP LOW-LEVEL LAPSE
   RATES ACROSS NORTHERN IN AND NORTHEAST IL.  NO MATTER IF STORMS ARE
   SURFACE BASED OR NOT...A LARGE HAIL THREAT WILL REMAIN...WITH
   DAMAGING WIND THREATS GENERALLY CONFINED TO AREAS WHERE CONVECTION
   DID NOT OCCUR EARLIER.
   
   ..RACY.. 04/25/2009
   
   
   ATTN...WFO...DTX...APX...IWX...GRR...LOT...
   
   LAT...LON   43028605 44288356 43998260 42808277 42088357 41558469
               41128591 41148738 41378858 42508726 43028605