MESOSCALE DISCUSSION 0559
   NWS STORM PREDICTION CENTER NORMAN OK
   1055 AM CDT SAT APR 25 2009
   
   AREAS AFFECTED...LOWER MI
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 181...
   
   VALID 251555Z - 251730Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 181
   CONTINUES.
   
   LEADING THUNDERSTORM LINE SEGMENT RAPIDLY WEAKENED ACROSS WESTERN
   LOWER MI SHORTLY AFTER 15Z WITH INITIAL REPORTS OF WIND GUSTS AROUND
   35 KTS ASSOCIATED WITH THE STORMS.  CURRENT ACTIVITY SHOULD EXIT
   INTO SOUTHWEST ONTARIO AFTER 18Z.
   
   MIXED SIGNALS CONTINUE ON THE OVERALL CONVECTIVE/SEVERE POTENTIAL
   THIS AFTERNOON.  AIR MASS CONTINUES TO DESTABILIZE ALONG/E OF THE
   TRAILING LINE OF ONGOING CONVECTION.  12Z WHITE LAKE SOUNDING STILL
   EXHIBITED CONSIDERABLE DRY AIR BELOW 700 MB.  BUT... SATELLITE BASED
   PRECIPITABLE WATER/12Z UPPER AIR ANALYSIS SUGGEST THAT THE COLUMN
   WILL CONTINUE TO MOISTEN WITH VALUES APPROACHING 1.25 INCHES THIS
   AFTERNOON.  THUS...TRAILING BAND OF THE LEAD STORMS MAY YET
   INTENSIFY BEFORE EXITING INTO ONTARIO.  MEANWHILE...12Z
   HIGH-RESOLUTION NMM SEEMS TO SUGGEST THAT UPSTREAM ACTIVITY EXITING
   THE CHICAGO/MILWAUKEE AREAS MAY BE THE PRIMARY POTENTIAL SEVERE
   EVENT FOR THIS AFTERNOON.
   
   GIVEN AT LEAST MODEST INSTABILITY/STEEP LAPSE RATE ENVIRONMENT
   COUPLED WITH A FAIRLY STRONG DEEP WEST-SOUTHWEST UNIDIRECTIONAL WIND
   REGIME...ANY LINEAR SEGMENT THAT CAN BECOME SUSTAINED WILL RUN THE
   RISKS FOR BOWING AND PRODUCING DAMAGING WINDS ALONG WITH LARGE HAIL.
    SEVERE RISKS SHOULD BE CONFINED TO AREAS ALONG/SOUTHEAST OF A LINE
   FROM MUSKEGON TO TAWAS CITY THROUGH THE AFTERNOON HOURS WITH THE
   HIGHEST PROBABILITIES GENERALLY SOUTH OF ROUTE 46.
   
   ..RACY.. 04/25/2009
   
   
   ATTN...WFO...DTX...APX...GRR...
   
   LAT...LON   43628588 45388294 45188139 43638091 42558173 42248315
               42198610 43628588