

000 

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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