SPC MESOSCALE DISCUSSION 1990 FOR MOST OF LOWER MI
CONCERNING...TORNADO WATCH 734...

VALID 092018Z - 092230Z

THUNDERSTORMS AREA EXPECTED TO CONTINUE INCREASING IN AREAL
COVERAGE AND INTENSITY THROUGH THE LATE AFTERNOON / EARLY EVENING
HOURS FROM IN/OH NWD INTO MI.  WIND DAMAGE AND ISOLATED TORNADOES
WILL CONTINUE TO BE THE MAIN THREAT.

EFFECTS OF UPPER LEVEL DYNAMICS / FORCING EVIDENT NOW AS STORMS
INCREASING AHEAD OF COLD FRONT FROM IN NWD INTO MI...AND THIS TREND
IS EXPECTED TO CONTINUE FOR THE NEXT SEVERAL HOURS.  LATEST SURFACE
ANALYSIS SHOWS GREATEST PRESSURE FALLS OVER NRN MI.  GREATEST LOW
LEVEL HELICITY IS ALSO IN THIS AREA...WHERE WINDS ARE BACKED. 
BACKED WINDS ARE ALSO EVIDENT ACROSS ERN MI...AHEAD OF PRE FRONTAL
CONVERGENT ZONE.  BEST TORNADIC POTENTIAL APPEARS TO BE IN THE NRN
AND ERN PORTIONS OF WW 734.  OTHERWISE...WIND DAMAGE WILL BE THE
MAIN THREAT.  

..JEWELL.. 09/09/01