

000 

WWUS20 KWNS 232214

SEL3

SPC WW 232214

COZ000-240500-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 643

NWS STORM PREDICTION CENTER NORMAN OK

415 PM MDT THU AUG 23 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EAST CENTRAL AND SOUTHEAST COLORADO



EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 415 PM UNTIL

1100 PM 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 55

STATUTE MILES EAST AND WEST OF A LINE FROM 30 MILES NORTHWEST OF

LIMON COLORADO TO 40 MILES EAST SOUTHEAST OF TRINIDAD COLORADO.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU3).



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 640...WW 641...WW 642...



DISCUSSION...THUNDERSTORMS DEVELOPING OVER THE FRONT RANGE WILL

LIKELY INTENSIFY THIS AFTERNOON/EVENING AS THE LOW LEVELS WARM OVER

THE HIGH PLAINS AND REDUCE CONVECTIVE INHIBITION.  THE NET RESULT

WILL BE MODERATE INSTABILITY E OF THE MOUNTAINS WHERE A RELATIVELY

MOIST UPSLOPE FLOW REGIME IS ESTABLISHED N OF A FRONT NEAR THE NM/CO

BORDER.  ADDITIONALLY...A MID-UPPER TROUGH AND ASSOCIATED JET WILL

OVERSPREAD CO THIS EVENING...CONTRIBUTING TO A FAVORABLE BACKGROUND

ENVIRONMENT FOR THUNDERSTORMS...AND SUFFICIENT VERTICAL SHEAR FOR

LONG-LIVED SUPERCELLS.  THOUGH AN ISOLATED TORNADO CANNOT BE RULED

OUT...LARGE HAIL AND DAMAGING WINDS 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 27020.





...THOMPSON

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