WATCHES: Severe Thunderstorm Watch Number 686

WWUS20 KWNS 240058
SEL6
SPC WW 240058
MNZ000-NDZ000-240700-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 686
NWS STORM PREDICTION CENTER NORMAN OK
750 PM CDT SUN SEP 23 2007

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

NORTHWEST MINNESOTA
EASTERN NORTH DAKOTA

EFFECTIVE THIS SUNDAY NIGHT AND MONDAY MORNING FROM 750 PM UNTIL
200 AM 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 25 MILES NORTHWEST OF
HALLOCK MINNESOTA TO 10 MILES EAST OF JAMESTOWN NORTH DAKOTA.
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU6).

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 685...

DISCUSSION...TSTMS NOW FORMING BETWEEN MBG AND JMS IN N NCNTRL SD/SE
ND EXPECTED TO MOVE/DEVELOP NNE ALONG LEAD COLD FRONT ASSOCIATED
WITH EJECTING GRT BASIN UPR TROUGH. SFC-BASED INSTABILITY HAS
PEAKED FOR THE DAY. BUT DECOUPLING/STRENGTHENING SSWLY LLJ AND
ASSOCIATED MASS FLUX CHANGES SUGGEST THAT SE ND STORMS SHOULD REMAIN
STRONG THROUGH THE EVENING. GIVEN 40 KT SSWLY DEEP SWLY SHEAR AND
POTENTIAL FOR EMBEDDED SUPERCELLS/SUSTAINED UPDRAFTS...ACTIVITY MAY
POSE A THREAT FOR HI WIND/MARGINALLY SVR HAIL 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 450. MEAN STORM MOTION
VECTOR 22040.

..CORFIDI

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