Severe Thunderstorm Warning 42, NWS Pendleton, OR

NORTHEAST OREGON/SOUTHEAST WASHINGTON FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
125 PM PDT SUN AUG 25 2002

SHORT TERM AND FIRE WEATHER...AN UPPER LEVEL SHORT WAVE WILL MOVE
ACROSS THE FORECAST AREA THIS AFTERNOON AND TONIGHT. DYNAMIC LIFT
AND INSTABILITY ASSOCIATED WITH THE WAVE WILL TRIGGER SCATTERED
SHOWERS AND THUNDERSTORMS AS THIS SYSTEM MOVES THROUGH. THE
THUNDERSTORMS THIS AFTERNOON AND TONIGHT WILL BE MOSTLY WET AS THE
AIR MASS OVER THE AREA IS RATHER MOIST. A WEAK MARINE PUSH WILL
BEGIN LATE THIS AFTERNOON ALONG THE EAST SLOPES OF THE CASCADES AND
THEN MOVE ACROSS THE REMAINDER OF THE FORECAST AREA THIS EVENING.
THIS WILL INCREASE WINDS TONIGHT AND USHER IN A MUCH MORE STABLE AIR
MASS FOR MONDAY. THE SHORT WAVE WILL MOVE INTO IDAHO AND MONTANA ON
MONDAY WITH NORTHERLY FLOW ALOFT ON THE BACK SIDE OF THE UPPER
TROUGH OVER THE FORECAST AREA. ON MONDAY MARGINAL INSTABILITY WILL
REMAIN OVER EXTREME NORTHEAST OREGON FOR POSSIBLE ISOLATED
THUNDERSTORMS...MAINLY OVER WALLOWA COUNTY. THE UPPER SHORT WAVE
WILL STALL OVER MONTANA ON MONDAY BEFORE DIGGING SOUTHWEST INTO
IDAHO AND SOUTHEAST OREGON ON TUESDAY. THIS WILL ALLOW SOME WRAP
AROUND MOISTURE TO RETURN TO EXTREME EASTERN OREGON FOR SOME SHOWERS
AND MOSTLY WET ISOLATED THUNDERSTORMS ON TUESDAY. THE AFOREMENTIONED
SHORT WAVE WILL MOVE INTO EASTERN OREGON ON WEDNESDAY FOR A CHANCE
OF MAINLY AFTERNOON AND EVENING SHOWERS AND MOSTLY WET THUNDERSTORMS
OVER THE MOUNTAINS OF NORTHEAST OREGON.  POLAN

IN THE EXTENDED...STUBBORN SHORT WAVE/MID LEVEL LOW PRESSURE OVER
EASTERN OREGON WILL BEGIN TO WEAKEN AND DRIFT INTO IDAHO THURSDAY.
BUT LINGERING MOISTURE REMAINS MAINLY OVER THE EASTERN FORECAST AREA
THAT INCLUDES THE BLUE AND WALLOWA MOUNTAINS...WHICH WILL SEE SOME
AFTERNOON AND EVENING THUNDERSTORMS. ALSO WITH THE EXITING LOW COMES
A LONG WAVE TROUGH ENTERING THE PACIFIC NORTHWEST COAST THURSDAY
AFTERNOON AND SOME ISOLATED THUNDERSTORMS MAY DEVELOP OVER THE
NORTHERN CASCADES NEAR GOLDENDALE LATE THURSDAY AND INTO THE
EVENING. DRIER AIR FILTERS INTO THE CASCADES FRIDAY BUT INSTABILITY
PERSISTS OVER THE WALLOWA AND BLUE MOUNTAINS WHERE ISOLATED
THUNDERSTORMS ARE POSSIBLE. AS THE TROUGH MOVES EAST AND AWAY FROM
THE THE AREA SATURDAY...MUCH DRIER AIR WILL INVADE ALL OF NORTHEAST
OREGON AND SOUTHEAST WASHINGTON AND A RETURN TO MOSTLY SUNNY AND
WARMER TEMPERATURES ARE LIKELY NEXT WEEKEND.

PDT 3000  ALW 3000  PSC 2000  YKM 2000

KPDT...VCP21/PRECIP MODE...OPERATIONAL.

.KPDT...NONE.