WATCHES: Severe Thunderstorm Watch Number 671

WWUS20 KWNS 180036
SEL1
SPC WW 180036
IAZ000-MNZ000-SDZ000-180600-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 671
NWS STORM PREDICTION CENTER NORMAN OK
740 PM CDT MON SEP 17 2007

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

NORTHWEST IOWA
MUCH OF MINNESOTA
SOUTHEAST SOUTH DAKOTA

EFFECTIVE THIS MONDAY NIGHT AND TUESDAY MORNING FROM 740 PM UNTIL
100 AM CDT.

HAIL TO 2 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 65
STATUTE MILES EAST AND WEST OF A LINE FROM 25 MILES NORTH OF
HIBBING MINNESOTA TO 45 MILES EAST SOUTHEAST OF YANKTON SOUTH
DAKOTA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED
WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).

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 ARE LIKELY TO STRENGTHEN THIS
EVENING ALONG SURFACE COLD FRONT FROM CENTRAL/NORTHERN MN INTO
EASTERN SD. THESE STORMS WILL ORGANIZE AND SPREAD NORTHEASTWARD
INTO EASTERN MN AND NORTHWEST IA BY MIDNIGHT. MODERATE INSTABILITY
IS IN PLACE OVER THIS REGION...ALONG WITH STRENGTHENING LOW/MID
LEVEL WIND FIELDS. THIS WILL SUPPORT A RISK OF SUPERCELLS
EARLY...TRANSITIONING INTO MULTICELL CLUSTERS. LARGE HAIL AND
DAMAGING WINDS ARE POSSIBLE IN STRONGER CELLS.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM
MOTION VECTOR 23035.

..HART

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