MESOSCALE DISCUSSION 1423
   NWS STORM PREDICTION CENTER NORMAN OK
   1204 PM CDT THU JUL 18 2013

   AREAS AFFECTED...NRN LOWER MI AND ADJACENT PORTIONS OF LAKE MI AND
   LAKE HURON

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

   VALID 181704Z - 181800Z

   PROBABILITY OF WATCH ISSUANCE...60 PERCENT

   SUMMARY...SVR TSTMS WILL INCREASE IN COVERAGE DURING THE AFTN HOURS
   WITH DAMAGING WINDS AND LARGE HAIL LIKELY. A WW IS PSBL IN THE NEXT
   COUPLE OF HOURS...AND MORE LIKELY LATER THIS AFTN.

   DISCUSSION...AN ISOLD SVR TSTM OVER MONTMORENCY COUNTY MI WILL
   CONTINUE MOVING ESE TOWARDS AREAS NEAR/S OF ALPENA WITH A THREAT FOR
   DAMAGING WINDS AND HAIL. THE ENVIRONMENT OVER NRN LOWER MI IS
   MODERATELY UNSTABLE AS SFC TEMPS HAVE WARMED INTO THE UPPER
   80S/LOWER 90S...AND ADDITIONAL DIURNAL HEATING WILL LEAD TO FURTHER
   DESTABILIZATION WITH TIME. FAIRLY UNIDIRECTIONAL LOW AND MID-LEVEL
   FLOW WILL RESULT IN SUFFICIENT SHEAR FOR ORGANIZED TSTMS CAPABLE OF
   DAMAGING WINDS AND POSSIBLY LARGE HAIL. EXPECT ADDITIONAL TSTMS TO
   DEVELOP ACROSS THE DISCUSSION AREA THIS AFTN...WITH MERGERS LEADING
   TO E/SEWD-MOVING LINES/BOWING SEGMENTS. A WW IS PSBL PRIOR TO
   19Z...AND MORE LIKELY BEYOND THAT TIME AS ORGANIZED TSTMS DEVELOP
   UPSTREAM AND MOVE TOWARDS NRN LOWER MI.

   ..BUNTING/CORFIDI.. 07/18/2013


   ATTN...WFO...DTX...APX...GRR...MQT...GRB...

   LAT...LON   45798497 45568348 45398269 45018247 44238231 43628236
               43458466 43508609 43778722 44778729 45618680 45798497