WATCHES: Severe Thunderstorm Watch Number 687

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

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