

000 

WWUS20 KWNS 101953

SEL7

SPC WW 101953

MIZ000-LHZ000-LMZ000-LSZ000-110300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 507

NWS STORM PREDICTION CENTER NORMAN OK

350 PM EDT TUE JUL 10 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EASTERN UPPER MICHIGAN AND MUCH OF NORTHERN AND WESTERN LOWER

MICHIGAN

MICHIGAN

       LAKE HURON

       LAKE MICHIGAN

       LAKE SUPERIOR



EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 350 PM UNTIL

1100 PM EDT.



HAIL TO 1 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 90

STATUTE MILES EAST AND WEST OF A LINE FROM 45 MILES NORTHEAST OF

PELLSTON MICHIGAN TO 5 MILES SOUTH SOUTHEAST OF GRAND RAPIDS

MICHIGAN.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).



REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE

FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH

AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR

THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS

AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY

DO PRODUCE TORNADOES.



OTHER WATCH INFORMATION...CONTINUE...WW 504...WW 505...WW 506...



DISCUSSION...SCATTERED THUNDERSTORMS HAVE FORMED ALONG A DIFFUSE

LAKE BREEZE ACROSS CENTRAL LOWER MI...WHERE SURFACE TEMPERATURES

HAVE REACHED 90 F AND MODERATE INSTABILITY IS PRESENT.  LOW-MID

LEVEL FLOW OF 30-35 KT MAY SUPPORT A FEW STORMS WITH DAMAGING GUSTS

AND MARGINALLY SEVERE HAIL THIS AFTERNOON...THOUGH STORM INTENSITY

MAY BE LIMITED SOME BY RATHER POOR MID LEVEL LAPSE RATES.  LATER

DURING THE AFTERNOON/EVENING...THE MORE ORGANIZED PRE-FRONTAL BANDS

OF CONVECTION OVER WI/WRN UPPER MI WILL MOVE EWD INTO LOWER MI.

SOME INCREASE IN LOW-MID LEVEL FLOW WITH THE APPROACHING MID LEVEL

TROUGH MAY TEND TO COMPENSATE FOR SLOW STABILIZATION OF THE BOUNDARY

LAYER BY LATE EVENING...AND MAINTAIN A THREAT FOR DAMAGING WINDS

INTO EARLY TONIGHT.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60 KNOTS.

A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM MOTION

VECTOR 26030.





...THOMPSON

