WATCHES: Severe Thunderstorm Watch Number 694

WWUS20 KWNS 292306
SEL4
SPC WW 292306
COZ000-KSZ000-NEZ000-300600-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 694
NWS STORM PREDICTION CENTER NORMAN OK
500 PM MDT SAT SEP 29 2007

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

EASTERN COLORADO
WESTERN KANSAS
SOUTHWEST AND CENTRAL NEBRASKA

EFFECTIVE THIS SATURDAY AFTERNOON FROM 500 PM UNTIL MIDNIGHT MDT.

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 50
STATUTE MILES EAST AND WEST OF A LINE FROM 20 MILES SOUTH
SOUTHEAST OF SPRINGFIELD COLORADO TO 10 MILES NORTH NORTHEAST OF
VALENTINE NEBRASKA. FOR A COMPLETE DEPICTION OF THE WATCH SEE
THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU4).

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...THUNDERSTORMS ARE DEVELOPING ALONG A LEE TROUGH/DRYLINE
ACROSS SE AND E CENTRAL CO WHERE SURFACE HEATING HAS BEEN STRONGEST
THIS AFTERNOON...DOWNSTREAM FROM THE PRIMARY MID LEVEL TROUGH THAT
IS APPROACHING THE CENTRAL ROCKIES. THIS CONVECTION WILL LIKELY
INCREASE IN COVERAGE AND INTENSITY WHILE SPREADING NEWD TOWARD NEB
THIS EVENING. MEANWHILE...OTHER STORMS MAY EVOLVE FROM THE MID
LEVEL CONVECTION NOW FORMING OVER WRN NEB. VERTICAL SHEAR OVER THE
WARM SECTOR IS SUFFICIENT FOR SUPERCELLS...WHILE RATHER MODEST
BOUNDARY LAYER MOISTURE SUGGESTS THAT DAMAGING WINDS AND LARGE HAIL
WILL BE THE MAIN SEVERE THREATS.

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 23040.

..THOMPSON

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