WATCHES: Tornado Watch Number 634

WWUS20 KWNS 212353
SEL4
SPC WW 212353
IAZ000-NEZ000-220700-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 634
NWS STORM PREDICTION CENTER NORMAN OK
650 PM CDT TUE AUG 21 2007

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

NORTHERN AND WESTERN IOWA
EASTERN NEBRASKA

EFFECTIVE THIS TUESDAY NIGHT AND WEDNESDAY MORNING FROM 650 PM
UNTIL 200 AM CDT.

TORNADOES...HAIL TO 2.5 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 85 STATUTE
MILES EAST AND WEST OF A LINE FROM 35 MILES NORTHEAST OF SPENCER
IOWA TO 30 MILES SOUTH OF DENISON IOWA. FOR A COMPLETE DEPICTION
OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS
WOU4).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND 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.

OTHER WATCH INFORMATION...CONTINUE...WW 630...WW 631...WW
632...WW 633...

DISCUSSION...SCTD STRONG SUPERCELLS IN NE NEB EXPECTED TO CONTINUE
GENERALLY ESE TOWARD WRN IA LATER THIS EVENING...WITH ADDITIONAL
STORMS POSSIBLY FORMING IN ZONER OF STRENGTHENING WAA DOWNSTREAM
ACROSS NRN IA. ACTIVITY IS ON SRN EDGE OF SEASONABLY STRONG WLY MID
LVL JET STREAK OVER CNTRL MN...AND MAY BE AIDED BY APPROACH OF JET
ENTRANCE REGION WITH THAT FEATURE LATER THIS EVENING. COUPLED WITH
VERY RICH LOW LVL MOISTURE AND FAIRLY STEEP MID LVL LAPSE
RATES...STORMS COULD YIELD VERY LARGE HAIL/HIGH WIND AND POSSIBLE
TORNADOES. THE ACTIVITY SHOULD CONSOLIDATE INTO ONE OR TWO
BANDS...WITH A CONTINUING THREAT FOR HIGH WIND/HAIL AND POSSIBLY A
SPIN-UP TORNADO LATER TONIGHT/EARLY WEDNESDAY.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
600. MEAN STORM MOTION VECTOR 29030.

..CORFIDI

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