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WWUS20 KWNS 281754

SEL1

SPC WW 281754

IDZ000-UTZ000-WYZ000-290000-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 631

NWS STORM PREDICTION CENTER NORMAN OK

1155 AM MDT SAT AUG 28 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       PARTS OF SOUTHEAST IDAHO

       NORTHERN UTAH

       MUCH OF WESTERN WYOMING



EFFECTIVE THIS SATURDAY MORNING AND EVENING FROM 1155 AM UNTIL

600 PM MDT.



HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 80

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 70

STATUTE MILES EAST AND WEST OF A LINE FROM 50 MILES NORTHWEST OF

CODY WYOMING TO 45 MILES EAST SOUTHEAST OF DUGWAY UTAH.  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.



DISCUSSION...STORMS EXPECTED TO DEVELOP RAPIDLY ACROSS THE WATCH AS

AIR MASS HAS BECOME MDTLY UNSTABLE WITH LITTLE REMAINING CONVECTIVE

INHIBITION.  WITH 40-50 KT OF SHEAR...STEEP MID LEVEL LAPSE RATES

AND MLCAPES AOA 1200 J/KG...SEVERE THUNDERSTORMS INCLUDING POSSIBLE

SUPERCELLS ARE LIKELY. PRIMARY THREAT WILL BE STRONG/DAMAGING WINDS

ENHANCED BY THE EXISTING GRADIENT WINDS ALONG WITH LARGE HAIL.

SEVERE THREAT WILL BE GREATEST WITH ANY SUPERCELL THAT DEVELOPS

INCLUDING POSSIBILITY OF A BRIEF TORNADO.



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

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70

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

MOTION VECTOR 23035.





...HALES

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