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471 

WWUS20 KWNS 301818

SEL7

SPC WW 301818

COZ000-NEZ000-WYZ000-010300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 577

NWS STORM PREDICTION CENTER NORMAN OK

1220 PM MDT THU JUN 30 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       CENTRAL AND NORTHEAST COLORADO

       WESTERN NEBRASKA PANHANDLE

       SOUTH-CENTRAL AND SOUTHEAST WYOMING



EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 1220 PM UNTIL

900 PM MDT.



HAIL TO 1.5 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 120

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 25 MILES SOUTH OF

CRAIG COLORADO TO 20 MILES NORTH NORTHEAST OF SIDNEY NEBRASKA.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU7).



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 576...



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

INTENSITY ACROSS WATCH AREA THIS AFTERNOON AS INTENSIFYING

LARGE-SCALE FORCING FOR ASCENT AND VERTICAL SHEAR ATTENDANT TO UT

VORTICITY MAXIMUM OVERSPREAD A STEEP LAPSE RATE ENVIRONMENT.  THE

STRENGTHENING DEEP-LAYER WIND FIELD AND DEEP...WELL-MIXED PBL WILL

PROMOTE STRONG DOWNDRAFT DEVELOPMENT AS WELL AS HAIL WITH THE MOST

INTENSE STORMS.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM

MOTION VECTOR 22030.





...MEAD

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