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497 

WWUS20 KWNS 111934

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SPC WW 111934

COZ000-NEZ000-120300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 454

NWS STORM PREDICTION CENTER NORMAN OK

135 PM MDT SUN JUL 11 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       FAR NORTHEAST COLORADO

       WESTERN NEBRASKA INCLUDING THE PANHANDLE



EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 135 PM UNTIL 900

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 75

STATUTE MILES EAST AND WEST OF A LINE FROM 35 MILES EAST

NORTHEAST OF CHADRON NEBRASKA TO 45 MILES WEST OF IMPERIAL

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.



OTHER WATCH INFORMATION...CONTINUE...WW 450...WW 451...WW

452...WW 453...



DISCUSSION...TSTMS ARE EXPECTED TO INCREASE IN COVERAGE AND

INTENSITY THIS AFTERNOON AND EVENING IN ADVANCE OF SHORT WAVE TROUGH

PROGRESSING EWD FROM ERN WY.  THOUGH BOUNDARY LAYER IS NOT

PARTICULARLY MOIST...THE PRESENCE OF STEEP LOW TO MIDLEVEL LAPSE

RATES IS RESULTING IN A MODERATELY UNSTABLE AIR MASS WITH MLCAPE OF

1000-1500 J/KG.  WHEN COMBINED WITH 40-45 KT OF DEEP WNWLY

SHEAR...SETUP WILL FAVOR THE DEVELOPMENT OF HIGH-BASED SUPERCELLS

AND BOWING STORM CLUSTERS WITH THE THREAT FOR DAMAGING WINDS AND

LARGE HAIL.



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 28030.





...MEAD

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