MESOSCALE DISCUSSION 1683
   NWS STORM PREDICTION CENTER NORMAN OK
   0442 PM CDT MON JUL 07 2003
   
   AREAS AFFECTED...ERN UPPER MI...NRN LM COASTAL WATERS
   
   CONCERNING...SEVERE THUNDERSTORM POTENTIAL 
   
   VALID 072142Z - 080015Z
   
   CLUSTER OF TSTMS NOW OVER PORTIONS ALGER/DELTA/LUCE COUNTIES MAY
   PRODUCE OCCASIONAL HAIL/GUSTS NEAR SEVERE LEVELS AS IT MOVES SLOWLY
   EWD AND SEWD TOWARD CHIPPEWA/MACKINAC COUNTIES.  SOME BACKBUILDING
   IS POSSIBLE TOWARD AREA NW ESC AS WELL.  WW NOT ANTICIPATED ATTM.
   
   TSTM DEVELOPMENT ACROSS THIS AREA PAST HOUR HAS BEEN RELATIVELY
   RAPID...AIDED BY WEAKENING CAP AND SOLENOIDAL ASCENT ALONG LS
   BOUNDARY.  SFC ANALYSIS INDICATES STREAMLINE CYCLONE OVER CENTRAL
   U.P. N-NW OF ESC...ALONG PREFRONTAL SFC TROUGH...AND INDICATING
   EFFECTIVE WRN LIMIT OF SIGNIFICANT CONVECTIVE POTENTIAL.  MODIFIED
   MODEL SOUNDINGS INDICATE 1000-1500 J/KG MLCAPE IN VERY NARROW
   CORRIDOR BETWEEN LS/LM LAKE BREEZES...ALONG WITH FAVORABLE VERTICAL
   SHEAR FOR BOTH ORGANIZED MULTICELLS AND BRIEF SUPERCELLS.  ROUGHLY
   150 J/KG 0-3 KM SRH AND 50-60 KT 0-6 KM SHEAR ARE ESTIMATED FROM
   MODIFIED MQT VWP HODOGRAPH AND RUC WINDS.  WRN  
   ACTIVITY MOVING OVER IMMEDIATE COASTAL AREAS OF
   DELTA/SCHOOLCRAFT/MACKINAC COUNTIES AND ADJACENT WATERS SHOULD
   DIMINISH AS IT INGESTS RELATIVELY STABLE AIR FROM LAKE. ERN TSTMS
   MAY PERSIST LONGER...MOVING WITH A LARGE COMPONENT PARALLEL TO SFC
   THETAE AXIS CORRESPONDING CLOSELY TO CENTER OF PENINSULA.
   
   ..EDWARDS.. 07/07/2003
   
   
   ATTN...WFO...APX...MQT...
   
   46158708 46198643 46518586 46578529 46388454 46068419
   45838465 45858553 45718629 45948703