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000 

WWUS20 KWNS 292025

SEL3

SPC WW 292025

MIZ000-WIZ000-LSZ000-300300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 773

NWS STORM PREDICTION CENTER NORMAN OK

325 PM CDT TUE JUL 29 2008



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       WESTERN UPPER MICHIGAN

       NORTHEAST WISCONSIN

       LAKE SUPERIOR



EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 325 PM UNTIL

1000 PM CDT.



HAIL TO 1.5 INCHES 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 70

STATUTE MILES EAST AND WEST OF A LINE FROM 35 MILES NORTH

NORTHWEST OF MARQUETTE MICHIGAN TO 30 MILES SOUTH OF MOSINEE

WISCONSIN.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).



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.



DISCUSSION...SCATTERED THUNDERSTORMS SHOULD INTENSIFY GRADUALLY

ALONG AND IN ADVANCE OF A COLD FRONT MOVING INTO NW WI...AND IN

ASSOCIATION WITH A WEAK LEAD SHORTWAVE TROUGH.  A WARMING AND

MOISTENING BOUNDARY LAYER WILL RESULT IN DESTABILIZATION FROM SW TO

NE FROM WI INTO UPPER MI...IN AN ENVIRONMENT WITH EFFECTIVE BULK

SHEAR OF 35-45 KT.  VERTICAL SHEAR AND INSTABILITY SHOULD BE

SUFFICIENT FOR A FEW SUPERCELLS CAPABLE OF PRODUCING DAMAGING WINDS

AND LARGE HAIL.  AN ISOLATED TORNADO CANNOT BE RULED OUT...GIVEN THE

MODERATELY STRONG LOW-LEVEL SHEAR AND MOIST BOUNDARY LAYER ON THE NE

EDGE OF THE STRONGER INSTABILITY.



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

TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

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

MOTION VECTOR 28025.





...THOMPSON

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