

000 

WWUS20 KWNS 312106

SEL4

SPC WW 312106

IDZ000-ORZ000-WAZ000-010400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 664

NWS STORM PREDICTION CENTER NORMAN OK

205 PM PDT FRI AUG 31 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHERN IDAHO

       CENTRAL AND NORTHEAST OREGON

       SOUTHEAST AND EAST CENTRAL WASHINGTON



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 205 PM UNTIL 900

PM PDT.



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 75

STATUTE MILES EAST AND WEST OF A LINE FROM 55 MILES WEST OF BURNS

OREGON TO 70 MILES EAST NORTHEAST OF EPHRATA WASHINGTON.  FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU4).



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...THUNDERSTORMS ARE BEGINNING TO INCREASE OVER CENTRAL

OREGON IN RESPONSE TO DYNAMIC FORCING ASSOCIATED WITH SHORT WAVE

TROUGH MOVING NEWD ALONG THE PACIFIC NORTHWEST COAST.  AIR MASS IS

CONTINUING TO WARM AND DESTABILIZE IN THE WAKE OF EARLIER CONVECTION

MOVING NEWD ACROSS NERN WA.  DEVELOPMENT OF A DEEP WELL-MIXED

BOUNDARY LAYER WILL ENHANCE POTENTIAL FOR DAMAGING WIND GUSTS...AND

40-45 KT DEEP LAYER SHEAR WILL PROMOTE THREAT FOR SUPERCELLS WITH

DAMAGING WINDS AND HAIL.  ACTIVITY IS EXPECTED TO SPREAD NEWD TOWARD

SERN WA AS MID/UPPER LEVEL JET STREAK LIFTS NEWD ACROSS AREA.



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 450. MEAN STORM

MOTION VECTOR 22030.





...WEISS

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