FXUS66 KPDT 271132 AAA
AFDPDT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
332 AM PST FRI NOV 27 2009

UPDATED AVIATION DISCUSSION

.SHORT TERM...TODAY THROUGH SATURDAY NIGHT...A SLOW MOVING COLD 
FRONT CONTINUES TO MOVE ACROSS THE FORECAST AREA THIS MORNING. MAIN 
FRONTAL PRECIPITATION BAND STRETCHES FROM NORTHERN CALIFORNIA ACROSS 
EASTERN OREGON TO FAR EASTERN WASHINGTON AND THE IDAHO PANHANDLE. 
PRECIPITATION ALONG THE EAST SLOPES OF THE CASCADES HAS DECREASED TO 
SHOWERS AT THIS TIME. AS THE FRONT CONTINUES TO SLOWLY MOVE EAST WE 
WILL SEE THIS TRANSITION FROM A STEADY PRECIPITATION TO SHOWERS ON A 
WEST TO EAST PROGRESSION. THE FRONT WON'T EXIT THE FORECAST AREA 
UNTIL LATE THIS AFTERNOON SO AREAS EAST OF JOHN DAY AND MEACHAM WILL 
SEE A STEADY PRECIPITATION UNTIL THIS AFTERNOON BEFORE TURNING OVER 
TO SHOWERS. OTHER THAN A FEW LINGERING SHOWERS NEAR THE IDAHO 
BORDER EARLY TONIGHT THE OVERNIGHT PERIOD LOOKS TO BE DRY AS HIGH 
PRESSURE BUILDS BACK OVER THE REGION FROM OFF THE PACIFIC OCEAN. 
THIS HIGH PRESSURE WILL DOMINATE THE WEATHER ON SATURDAY FOR MOST OF 
THE FORECAST AREA. HOWEVER...A WARM FRONT WILL BE CLIPPING WESTERN 
WASHINGTON SO COULD SEE SOME LIGHT RAIN AND SNOW NEAR THE SNOQUALMIE 
PASS AREA OTHERWISE JUST SOME MID AND HIGH LEVEL CLOUDS ON 
SATURDAY.    

.LONG TERM...SUNDAY THROUGH THURSDAY. AN UPPER LEVEL RIDGE WILL 
BUILD OVER THE PACIFIC NORTHWEST SUNDAY. AN UPPER LEVEL TROUGH WILL 
APPROACH THE PACIFIC NORTHWEST MONDAY..AND FLATTEN THE RIDGE AS IT 
MOVES THROUGH MONDAY NIGHT WITH A CHANCE OF RAIN AND MOUNTAIN SNOW. 
THE UPPER RIDGE WILL REBUILD OFFSHORE AREA TUESDAY AND MOVE SLOWLY 
EAST OVER WASHINGTON AND OREGON WEDNESDAY AND THURSDAY. NORTHWEST 
FLOW MAY KEEP A FEW SHOWERS IN THE NORTHEAST OREGON MOUNTAINS 
TUESDAY. THE GFS AND ECMWF HAVE VERY DIFFERENT TIMING AND TRACK OF A 
CUTOFF LOW UNDERCUTTING THE RIDGE...WITH THE GFS MOVING THE CUTOFF 
OVER OREGON AND THE ECMWF MOVING IT THROUGH CALIFORNIA. WITH WIDELY 
DIFFERENT SOLUTIONS MADE NO CHANGES TO CURRENT EXTENDED FORECAST 
BASED ON THE RIDGE MAINTAINING ITSELF. KEPT PARTLY CLOUDY SKIES WITH 
PATCHY FOG DEVELOPING IN THE COLUMBIA BASIN AND ADJACENT VALLEYS 
WEDNESDAY AND THURSDAY. 

&&

.AVIATION...12Z TAFS...MVFR CONDITIONS WILL BE PREVALENT THIS  
MORNING AT ALL TAF SITES EXCEPT KRDM DUE TO RAIN/FOG ASSOCIATED WITH 
A VERY SLOW MOVING FRONTAL SYSTEM. IFR IS POSSIBLE AT TIMES UNTIL 
18Z. CEILINGS AND VISIBILITY WILL GRADUALLY IMPROVE FROM WEST TO 
EAST. STEADY RAIN WILL TAPER OFF TO SHOWERS DURING THE 
MORNING...ENDING BY THE AFTERNOON. CLEARING SKIES THIS AFTERNOON AND 
EVENING WILL ALLOW FOG TO REDEVELOP NEAR KPSC...AND POSSIBLY KDLS 
AND KALW. 76

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  51  30  46  32 /  60  10   0   0 
ALW  50  32  47  35 /  60  10   0   0 
PSC  50  29  46  30 /  30  10   0   0 
YKM  51  25  46  29 /  20   0   0   0 
HRI  51  29  46  29 /  30  10   0   0 
ELN  48  27  46  32 /  20   0   0  10 
RDM  46  25  45  23 /  30  10   0   0 
LGD  44  27  40  27 /  80  10   0   0 
GCD  43  26  40  29 /  70  10   0   0 
DLS  52  33  48  33 /  20   0   0   0 

&&

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

THREAT INDEX
TODAY : GREEN
SATURDAY : GREEN
SUNDAY : GREEN

GREEN: NONE OR LIMITED NEED FOR WATCHES, WARNINGS, OR ADVISORIES.
YELLOW: A FEW WATCHES, WARNINGS, OR ADVISORIES POSSIBLE OR IN EFFECT.
RED: NUMEROUS WATCHES, WARNINGS, OR ADVISORIES POSSIBLE OR IN EFFECT.

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

$$

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