Flash Flood Warning 5, NWS Pendleton, OR

NORTHEAST OREGON/SOUTHEAST WASHINGTON FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
230 PM PDT SAT AUG 24 2002

FIRE WEATHER CONCERN WILL BE WITH THUNDERSTORM ACTIVITY NEXT COUPLE
OF DAYS.

THUNDERSTORMS WERE ALREADY DEVELOPING OVER THE SOUTHERN PORTIONS OF
THE COUNTY WARNING AREA NEAR JOHN DAY AND ACROSS THE NORTHERN
FORECAST AREA WHERE THE MOISTURE PLUME IS. ALTHOUGH WEAKER THAN
YESTERDAY...LOW/MID LEVEL LOW PRESSURE OVER SOUTHERN OREGON WAS
RESPONSIBLE FOR THE ACTIVITY. IT APPEARS THAT THE MODELS WERE
UNDERDOING THE MOISTURE AND WILL INCREASE POPS FROM MOS TONIGHT AND
GO SCATTERED ACROSS ALL AREAS WITH LIKELY OVER THE WALLOWA AND BLUE
MOUNTAINS.

THE MODELS SEEM TO BE COMING TO AN AGREEMENT WITH THE NEXT SYSTEM
MOVING ONSHORE. THE FAVORABLE AVN SOLUTION HAS A MID LEVEL TROUGH
ENTERING THE WASHINGTON COAST SUNDAY WITH UNSTABLE CONDITIONS
PERSISTING ACROSS OUR AREA. THE NEW MESO ETA HAS SOME VEERING WITH
HEIGHT FROM THE JOHN DAY AREA FORECAST SOUNDING. THIS AREA ALSO
MAY BE IN A FAVORABLE REGION OF AN UPPER LEVEL JET AND WITH A
SOUTHWEST FLOW SOME OF THE STORMS COULD BECOME STRONG.

SUNDAY NIGHT THERE IS A STABLE AND COOLER MARINE PUSH OF AIR MOVING
INTO THE WESTERN FORECAST AREA NEAR THE DALLES AND SPREADS EAST INTO
THE BASIN BY MONDAY MORNING. THE EXCEPTION IS OVER THE EASTERN
FORECAST AREA SUCH AS THE WALLOWA MOUNTAINS WHERE INSTABILITY
PERSISTS AND I WILL KEEP THE MENTION OF ISOLATED THUNDERSTORMS.

FROM THE MID LEVEL TROUGH...A MID LEVEL LOW DEVELOPS AND DRIFTS INTO
NORTHEAST OREGON MONDAY AFTERNOON AND UNSTABLE CONDITIONS CONTINUE
OVER THE WALLOWA MOUNTAINS. THE LOW CREEPS INTO SOUTHEAST OREGON
TUESDAY AND A SOUTHEAST UPSLOPE FLOW DEVELOPS OVER THE JOHN DAY AND
WALLOWA MOUNTAINS. MID LEVEL MOISTURE INCREASES AND WITH DAYTIME
HEATING I WILL MENTION POPS FOR THIS AREA.

TEMPERATURES SUNDAY WILL BE NEAR NORMAL WITH COOLER AFTERNOON HIGHS
EXPECTED FOR MONDAY WITH THE BREEZY AND COOLER MARINE AIR MOVING
INTO MOST PORTIONS OF THE AREA. BY TUESDAY LOW LEVEL TEMPERATURES
INCREASE AND AFTERNOON HIGHS SHOULD DO THE SAME CLIMBING INTO THE
MID/UPPER 80S ACROSS THE BASIN.

EXTENDED...EXTENDED MODELS EARLY THIS MORNING WERE STARTING TO COME
INTO LINE WITH YESTERDAY/S AFTERNOON AVN RUN...WHICH WAS TO BRING AN
UPPER LEVEL LOW TO SOUTHEAST OREGON ON WEDNESDAY. THEN THE NEW AVN
RUN CAME IN AND MOVED THE UPPER LEVEL LOW FARTHER SOUTH TO NORTHWEST
NEVADA. CANADIAN ENSEMBLE ALSO SHOWED A LEANING TOWARDS THIS
SOLUTION. SINCE THE CURRENT FORECAST WAS FOR A COMPROMISE SITUATION
LIKE THIS...I HAVEN/T MADE MANY CHANGES. HOWEVER...CONFIDENCE IS
STILL LOW...ESPECIALLY IN THE DAY 6 AND 7 AS ANOTHER TROUGH ENTERS
THE PACIFIC NORTHWEST. TIMING AND POSITION OF THIS TROUGH WILL
DETERMINE WHETHER OR NOT THE AREA WILL BE STABLE OR UNSTABLE. HAVE
COMPROMISED ON A SOLUTION HERE AS WELL BY KEEPING IN A SLIGHT CHANCE
OF PRECIPITATION ON FRIDAY AND MOSTLY CLOUDY SKIES THROUGH SATURDAY.
JR

PDT 3331  ALW 3331  PSC 3331  YKM 3331

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

.KPDT...NONE.