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WWUS20 KWNS 281940

SEL7

SPC WW 281940

IDZ000-ORZ000-290300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 547

NWS STORM PREDICTION CENTER NORMAN OK

140 PM MDT WED JUL 28 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       MUCH OF SOUTHERN IDAHO

       PARTS OF SOUTHEAST OREGON



EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 140 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 80

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 70 MILES WEST

SOUTHWEST OF BOISE IDAHO TO 25 MILES EAST NORTHEAST OF IDAHO

FALLS IDAHO.  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 545...WW 546...



DISCUSSION...AS UPPER TROUGH MOVES NNEWD THRU ERN OR/WRN ID...AIR

MASS ACROSS THE WATCH AREA HAS DESTABILIZED.  THUNDERSTORMS

CURRENTLY DEVELOPING ALONG HIGHER TERRAIN AND WILL INCREASE IN

NUMBER/INTENSITY AS THEY MOVE ACROSS SNAKE RIVER VALLEY WHERE AIR

MASS MOST UNSTABLE WITH MLCAPES AOA 1000 J/KG.  IN ADDITION TO LARGE

HAIL...DAMAGING WINDS WILL BE POSSIBLY WITH STRONGER STORMS.

SUFFICIENT LOW LEVEL SHEAR TO SUPPORT THE DEVELOPMENT OF A COUPLE

SUPERCELLS WHICH WOULD ENHANCE THE SEVERE THREAT  FURTHER.



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 19025.





...HALES

