

000 

WWUS20 KWNS 242201

SEL7

SPC WW 242201

IAZ000-MNZ000-WIZ000-LSZ000-250500-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 687

NWS STORM PREDICTION CENTER NORMAN OK

500 PM CDT MON SEP 24 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHERN IOWA

       EASTERN AND SOUTHERN MINNESOTA

       WESTERN AND NORTHERN WISCONSIN

       LAKE SUPERIOR



EFFECTIVE THIS MONDAY AFTERNOON FROM 500 PM UNTIL MIDNIGHT CDT.



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 65

STATUTE MILES EAST AND WEST OF A LINE FROM 50 MILES NORTH

NORTHEAST OF KENNEDY WISCONSIN TO 30 MILES SOUTHWEST OF MASON

CITY IOWA.  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.



DISCUSSION...BANDS OF TSTMS...WITH POSSIBLE EMBEDDED

SUPERCELLS...EXPECTED TO DEVELOP NE AHEAD OF APPARENT LOW AMPLITUDE

SHORTWAVE IMPULSE LIFTING NE ACROSS SE SD/IA.  SEASONABLY STRONG

SWLY BACKGROUND FLOW AND HEATING/LOW LVL CONVERGENCE ALONG

ASSOCIATED COLD FRONT APPEAR FAVORABLE FOR STRONG WINDS/MARGINALLY

SVR HAIL.  FARTHER E...MORE ISOLATED CELLS IN ZONE OF WEAKER

CONVERGENCE ALONG PREFRONTAL CONFLUENCE AXIS IN NW WI MAY POSE A

THREAT FOR LOCALLY DAMAGING WIND AND PERHAPS A BRIEF TORNADO.



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 22035.





...CORFIDI

