MESOSCALE DISCUSSION 1421
   NWS STORM PREDICTION CENTER NORMAN OK
   0512 PM CDT SUN JUL 08 2007
   
   AREAS AFFECTED...NRN LOWER AND ERN UPPER MI
   
   CONCERNING...SEVERE POTENTIAL...SEVERE THUNDERSTORM WATCH LIKELY 
   
   VALID 082212Z - 082315Z
   
   DOWNSTREAM OF WW 492...AIR MASS REMAINS QUITE UNSTABLE ACROSS NRN
   LOWER MI WITH STRONG DEEP-LAYER SHEAR. ONGOING CLUSTERS OF STRONG TO
   SEVERE TSTMS OVER NRN WI/CNTRL UPPER MI WILL LIKELY CONTINUE EWD
   THROUGH THE EVENING...NECESSITATING A SEVERE TSTM ISSUANCE BY 23Z.
   
   AS OF 2205Z...RADAR/SATELLITE IMAGERY DEPICTED SEVERAL
   CLUSTERS/BANDS OF STRONG TO OCCASIONALLY SEVERE TSTMS ALONG A
   SLOW-MOVING COLD FRONT FROM E-CNTRL MN E/NEWD THROUGH CNTRL UPPER
   MI. WITH 40 TO 50 KTS OF MID-LEVEL WLY FLOW....THESE TSTMS SHOULD
   CONTINUE EWD ACROSS UPPER MI AND EVENTUALLY INTO NRN LOWER MI
   TOWARDS 02Z. ALTHOUGH CONVECTION FROM EARLIER TODAY AND ONSHORE FLOW
   FROM LKS MI AND HURON HAVE STABILIZED THE SURFACE LAYER ACROSS ERN
   UPPER MI...A THREAT FOR ELEVATED SUPERCELLS WILL LIKELY EXIST GIVEN
   THE STRONG DEEP-LAYER SHEAR. FARTHER S ACROSS NRN LOWER MI...NEARLY
   CLOUD FREE HEATING HAS RESULTED IN A VERY UNSTABLE AIR MASS WITH
   MLCAPES OF 2500 TO 3500 J/KG AWAY FROM THE IMMEDIATE COASTLINE /PER
   LATEST RUC OBJECTIVE ANALYSIS/. ALTHOUGH DIURNAL COOLING WILL RESULT
   IN SOME STABILIZATION...THE THREAT FOR LARGE HAIL AND DAMAGING WINDS
   SHOULD STILL BE MAINTAINED GIVEN THE ORGANIZED NATURE OF THE
   CONVECTION OVER NRN WI.
   
   ..GRAMS.. 07/08/2007
   
   
   ATTN...WFO...DTX...APX...GRR...MQT...
   
   46728469 45688322 44578270 43788394 43878577 44278652
   45418632 46488543