

637 

WWUS20 KWNS 232215

SEL2

SPC WW 232215

AZZ000-CAZ000-NVZ000-240600-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 732

NWS STORM PREDICTION CENTER NORMAN OK

410 PM MDT SUN AUG 23 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       WESTERN ARIZONA

       SOUTHEASTERN CALIFORNIA

       SOUTHERN NEVADA



EFFECTIVE THIS SUNDAY AFTERNOON FROM 410 PM UNTIL MIDNIGHT 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 70

STATUTE MILES EAST AND WEST OF A LINE FROM 25 MILES WEST

NORTHWEST OF SAINT GEORGE UTAH TO 10 MILES SOUTHEAST OF BLYTHE

CALIFORNIA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU2).



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...SCTD TSTMS EXPECTED TO CONTINUE FORMING THROUGH THIS

EVE IN ZONE OF HIGH PW DOWNSTREAM FROM TWO-PART UPR IMPULSE NOW

EXTENDING FROM SRN CA SWD INTO NRN BAJA.  MODERATE UNIDIRECTIONAL

CLOUD LAYER FLOW WITH STEEP MID LVL LAPSE RATES AND FAIRLY RICH

MOISTURE SUPPLY SUGGESTS POTENTIAL FOR REGENERATIVE/SUSTAINED STORMS

AND POSSIBLY A SUPERCELL OR TWO THAT COULD YIELD SVR HAIL/WIND.  THE

CONVECTION COULD ORGANIZE INTO SMALL CLUSTERS/BANDS BY MID EVE.



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 23020.





...CORFIDI

