

952 

WWUS20 KWNS 201837

SEL9

SPC WW 201837

IDZ000-MTZ000-ORZ000-WAZ000-210300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 499

NWS STORM PREDICTION CENTER NORMAN OK

1140 AM PDT FRI JUL 20 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHERN IDAHO

       NORTHWEST MONTANA

       EXTREME NORTHEAST OREGON

       CENTRAL AND EASTERN WASHINGTON



EFFECTIVE THIS FRIDAY MORNING AND EVENING FROM 1140 AM UNTIL 800

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 130

STATUTE MILES EAST AND WEST OF A LINE FROM 90 MILES EAST

NORTHEAST OF OMAK WASHINGTON TO 50 MILES SOUTH OF LEWISTON IDAHO.

 FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU9).



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...SCATTERED THUNDERSTORMS ARE BEGINNING TO INTENSIFY

ACROSS PARTS OF NORTHERN ORE AND CENTRAL WA...AHEAD OF AN

APPROACHING MID LEVEL SHORTWAVE TROUGH.  STRONG HEATING ACROSS THIS

REGION WILL RESULT IN STEEPENING LOW LEVEL LAPSE RATES AND A

MODERATELY UNSTABLE AIR MASS.  SUFFICIENT VERTICAL SHEAR MAY RESULT

IN A FEW ORGANIZED/ SUPERCELL STORMS OR BOWING STRUCTURES CAPABLE OF

DAMAGING WINDS AND LARGE HAIL.



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.





...HART

