

082 

WWUS20 KWNS 142029

SEL1

SPC WW 142029

COZ000-KSZ000-NEZ000-150300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 781

NWS STORM PREDICTION CENTER NORMAN OK

230 PM MDT SUN AUG 14 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHEAST COLORADO

       NORTHWEST KANSAS

       WESTERN NEBRASKA



EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 230 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 90

STATUTE MILES EAST AND WEST OF A LINE FROM 60 MILES NORTH

NORTHEAST OF ALLIANCE NEBRASKA TO 15 MILES SOUTHEAST OF

BURLINGTON COLORADO.  FOR A COMPLETE DEPICTION OF THE WATCH SEE

THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).



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 779...WW 780...



DISCUSSION...THUNDERSTORMS HAVE ALREADY DEVELOPED ALONG A SURFACE

BOUNDARY NEAR THE CO/NEB/WY BORDER...AND ADDITIONAL DEVELOPMENT IS

UNDERWAY FARTHER S INTO NE CO.  STORM COVERAGE SHOULD INCREASE THIS

AFTERNOON WITH CONTINUED SURFACE HEATING...AND WEAK ASCENT WITH THE

APPROACH OF A MIDLEVEL WAVE FROM WRN CO.  THE COMBINATION OF

MODERATE INSTABILITY AND EFFECTIVE BULK SHEAR OF 35-45 KT WILL

SUPPORT AN INITIAL RISK OF SUPERCELLS...WITH LARGE HAIL THE MAIN

THREAT.  STORM MERGERS COULD LEAD TO UPSCALE GROWTH INTO A CLUSTER

THIS EVENING AS THE LLJ INCREASES...WITH SOME INCREASE IN THE

DAMAGING WIND RISK.



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 550. MEAN STORM

MOTION VECTOR 29025.





...THOMPSON

