000
FXUS66 KPDT 160326
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
825 PM PDT SUN MAR 15 2009

.UPDATE...RADAR IMAGERY SHOWS A BAND OF RAIN AND SNOW ACROSS THE
BLUE MOUNTAINS AND EASTWARD...AS WELL AS SHOWERS WEST OF THE
CASCADES. THE FRONT ACROSS THE BLUE MOUNTAINS WILL CONTINUE TO MOVE
EAST TONIGHT. WITH A MORE WESTERLY WIND BEHIND THE FRONT...THE
COLUMBIA BASIN AND SURROUNDING VALLEYS WILL BE RAIN SHADOWED
TONIGHT...WITH ONLY SCATTERED SHOWERS FOR THE HIGHER TERRAIN. WINDS
ARE ALSO ON THE DECREASE ACROSS THE REGION...THOUGH THERE ARE
POCKETS OF 20 TO 30 MPH WINDS ACROSS PORTIONS OF THE YAKIMA VALLEY
AND NORTHERN BENTON COUNTY. BUT OVERALL...WINDS ARE ON THE DOWNWARD
TREND...THUS LET THE WIND ADVISORIES AND WARNING EXPIRE AT 8 PM PDT.
HAVE UPDATED THE FORECAST TO REFLECT DECREASING WINDS AND PLAN TO
UPDATE LATER TONIGHT TO REMOVE EVENING WORDING. OTHERWISE FORECAST
LOOKS TO BE ON TRACK. DMH

&&

.PREV DISCUSSION... /ISSUED 350 PM PDT SUN MAR 15 2009/

SHORT TERM...TONIGHT THROUGH TUESDAY...MAIN CONCERN CONTINUES TO BE
A STRONG UPPER LEVEL JET STREAM AND AN ASSOCIATED LOW LEVEL JET
STREAK OVER THE FORECAST AREA THROUGH MONDAY. SURFACE PRESSURE
GRADIENTS WILL INCREASE THIS AFTERNOON IN THE LOWER COLUMBIA BASIN
AND THE FOOTHILLS OF THE BLUE MOUNTAINS AND WILL CONTINUE VERY TIGHT
THROUGH THIS EVENING WITH ONGOING 6-HOUR PRESSURE RISES ON THE ORDER
OF 10 MB FROM 2 PM ONWARDS UNTIL AROUND MIDNIGHT. A WIND ADVISORY IS
IN EFFECT UNTIL 8 PM PDT THIS EVENING FOR THE LOWER COLUMBIA
BASIN...  THE FOOTHILLS OF THE BLUE MOUNTAINS AND PORTIONS OF
GILLIAM AND WHEELER COUNTIES. A HIGH WIND WARNING REMAINS IN EFFECT
FOR CENTRAL AND NORTH CENTRAL OREGON AND THE EAST SLOPES OF THE
SOUTHERN WASHINGTON CASCADES UNTIL 8 PM PDT THIS EVENING. BLOWING
DUST IN THE LOWER YAKIMA VALLEY OF YAKIMA COUNTY...IN BENTON COUNTY
AND IN THE LOWER COLUMBIA BASIN WILL CONTINUE INTO THIS EVENING.
LOCAL VISIBILITIES WILL BE REDUCED TO 1/4 MILE THIS AFTERNOON IN THE
WIND ADVISORY AREA. THE UPPER LEVEL JET STREAM BEGINS MOVING NORTH
MONDAY NIGHT AND EXITS THE FORECAST AREA LATE MONDAY NIGHT. BREEZY
WILL BE POSSIBLE ON MONDAY WITH WINDY CONDITIONS IN THE MOUNTAINS.
OTHERWISE...MOISTURE ASSOCIATED WITH THE JET WILL KEEP A CHANCE OF
RAIN AND MOUNTAIN SNOW IN THE FORECAST AREA THROUGH MONDAY AS
ANOTHER UPPER LEVEL SHORT WAVE MOVES INTO THE PACIFIC NORTHWEST. ON
TUESDAY A MID/UPPER LEVEL SPLIT FLOW DEVELOPS OVER THE PACIFIC
NORTHWEST WITH WESTERLY FLOW ALOFT EAST OF THE CASCADES THUS GIVING
THE FORECAST AREA DOWNSLOPE WINDS AND SUBSIDENCE IMMEDIATELY EAST OF
THE CASCADES.  POLAN

LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...PERIODS OF RAIN...AS
WELL AS HIGHER ELEVATION SNOW...WILL BE POSSIBLE ON TUESDAY NIGHT
AND WEDNESDAY AS ZONAL FLOW BRINGS PACIFIC MOISTURE INTO THE REGION.
ALTHOUGH THE MEDIUM RANGE MODELS ARE IN GENERAL AGREEMENT DURING
THIS PERIOD...DETAIL DIFFERENCES DO EXIST. THE 12Z GFS IS MUCH
WETTER THAN THE 12Z ECMWF...ESPECIALLY OVER EASTERN OREGON.
HOWEVER...SOUTHERLY LOW LEVEL WILL ALLOW SNOW LEVELS TO RISE TO
5000+ FEET...DIMINISHING THE CHANCES FOR SIGNIFICANT SNOW
ACCUMULATIONS SHOULD THE GFS VERIFY. YET ALONG THE EAST SLOPES OF
THE WASHINGTON CASCADES...SNOW LEVELS WILL REMAIN BELOW 3000
FEET...AND SEVERAL INCHES OF SNOW CAN BE EXPECTED.

ON THURSDAY AND FRIDAY...DRIER CONDITIONS CAN BE EXPECTED...ALTHOUGH
MOUNTAIN SHOWERS WILL STILL BE POSSIBLE. THEN ON SATURDAY...A DEEP
TROUGH WILL MOVE INTO THE REGION...BRINGING WIDESPREAD PRECIPITATION
THAT IS LIKELY TO PERSIST THROUGH SUNDAY.  82

AVIATION...00Z TAFS...VFR CONDITIONS WILL PREVAIL AT ALL TAF SITES
FOR THE NEXT 24 HOURS. HOWEVER...OCCASIONAL MVFR WILL BE POSSIBLE IN
RAIN SHOWERS AT KPSC...KALW AND KPDT THROUGH THIS EVENING. VERY
STRONG SOUTHWEST WINDS WILL PERSIST THROUGH AT LEAST
03Z...DIMINISHING OVERNIGHT. SKIES WILL REMAIN PARTLY CLOUDY UNDER
SCATTERED AND BROKEN MID LEVEL CLOUDS.  82

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  33  50  32  48 /  40  20  10  30
ALW  34  51  33  50 /  40  40  20  30
PSC  35  51  34  52 /  10  10  10  20
YKM  31  49  30  50 /  10  10  10  20
HRI  33  52  32  52 /  20  10  10  20
ELN  25  42  24  46 /  10  20  20  30
RDM  29  44  28  47 /  30  30  10  30
LGD  34  44  33  47 /  30  30  20  40
GCD  32  46  31  47 /  30  40  30  40
DLS  33  46  32  48 /  20  20  20  20

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
&&

$$

TI:GGG
FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT...
WWW.WEATHER.GOV/PENDLETON
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