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FXUS66 KPDT 250539 AAA
AFDPDT
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
939 PM PST TUE NOV 24 2009
UPDATED AVIATION DISCUSSION.
.UPDATE...A QUIET WEATHER NIGHT IS UNDERWAY AS WEAK RIDGING BUILDS
OVER THE PACIFIC NORTHWEST. THIS IS SHOVING MOISTURE AND ENERGY INTO
BRITISH COLUMBIA AND ONLY SOME HIGH CLOUDINESS IS GETTING INTO THE
WASHINGTON PORTION OF THE FORECAST AREA. HAVE CUT BACK ON CLOUD
COVER TONIGHT AND TOMORROW...MAINLY IN THE SOUTHERN THIRD OF THE
AREA. WITH REDUCED CLOUD COVER...TEMPERATURES HAVE DROPPED QUICKLY
TONIGHT TO WITHIN SEVERAL DEGREES OF FORECAST LOW TEMPERATURES. DEW
POINT TEMPERATURES SUGGEST THAT THEY WON`T DROP TOO MUCH FURTHER BUT
HAVE ADJUSTED SEVERAL LOCATIONS DOWN 2 OR 3 DEGREES TONIGHT. WINDS
REMAIN GENERALLY LIGHT ASIDE FROM THE GRANDE RONDE VALLEY. THE
GRANDE RONDE VALLEY HAS SEEN PRESSURE GRADIENTS RELAX TEMPORARILY
THIS EVENING AND WINDS HAVE DROPPED TO 15 TO 25 MPH FOR THE MOST
PART. PRESSURE GRADIENTS ARE FORECAST TO INCREASE AGAIN IN THE NEXT
FEW HOURS SO CURRENT WIND ADVISORY WILL REMAIN IN EFFECT. FORECAST
UPDATE FOR CLOUD COVER AND WINDS OUT SHORTLY. PERRY
&&
.AVIATION...VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS WITH
MAINLY HIGH CLOUDS ABOVE 15000 FT AGL. AN EXCEPTION MAY BE PATCHY
FOG TOMORROW MORNING BETWEEN 25/12Z AND 25/18Z CREATING POSSIBLE
MVFR VISIBILITIES ALONG RIVERS IN THE COLUMBIA BASIN AFFECTING
KYKM...KDLS AND KPSC. SURFACE WINDS WILL REMAIN UNDER 15 KTS AT ALL
TAF LOCATIONS FOR THE NEXT 24 HOURS. PERRY
&&
.PREV DISCUSSION... /ISSUED 230 PM PST TUE NOV 24 2009/
SHORT TERM...TONIGHT THROUGH FRIDAY. A WEAK UPPER LEVEL RIDGE HAS
MOVED OVER WA/OR KEEPING MOST OF THE AREA DRY THROUGH LATE
WEDNESDAY. THE ONLY EXCEPTION WILL BE ALONG THE EAST SLOPES OF THE
WASHINGTON CASCADES. A DEEP UPPER TROUGH OFF THE GULF OF ALASKA
WILL SAG SOUTHWARD OVER THE NEXT 24 HOURS AND SPREAD PRECIPITATION
OVER WESTERN WASHINGTON WITH SOME MOISTURE SPREADING JUST EAST OF
THE CASCADE CREST. BELIEVE PRECIPITATION WILL FALL AS RAIN ALONG
THE EASTERN VALLEYS AS SNOW LEVELS ARE HIGH AND TEMPERATURES SHOULD
REMAIN ABOVE FREEZING. MEANWHILE...PARTLY CLOUDY SKIES ARE EXPECTED
OVER THE REMAINDER OF THE REGION TONIGHT AND WEDNESDAY. ONE CHANGE
IN THE FORECAST WAS TO DOWNPLAY THE FOG FOR TONIGHT AND WEDNESDAY
NIGHT. FOR TONIGHT...THE INVERSION WILL STRENGTHEN YET THE LOW
LEVEL MOISTURE IS LACKING FOR ANY FOG DEVELOPMENT EXCEPT FOR PATCHY
GROUND FOG ALONG THE RIVERS. I ALSO FEEL THAT SUNDAY`S WIND EVENT
HAS KEPT THE AIR MASS FAIRLY WELL MIXED. ON WEDNESDAY NIGHT...MID
LEVEL CLOUDS WILL INCREASE AND SURFACE WINDS WILL INCREASE ALONG THE
BLUE MTN FOOTHILLS...SO THE THREAT OF FOG IS MINIMAL.
PREVIOUS MODEL RUNS HAD SIGNIFICANT DIFFERENCES IN THE POSITION AND
STRENGTH OF AN APPROACHING SYSTEM AT THE START OF THE THANKSGIVING
HOLIDAY. 12Z GFS AND ECMWF ARE IN MUCH BETTER AGREEMENT AND WERE
PREFERRED OVER THE OUTLIER NAM MODEL. A MOIST WARM FRONT IS PROGGED
TO SPREAD RAIN OVER CENTRAL WASHINGTON WEDNESDAY NIGHT. THE FRONT
WILL MOVE NORTH INTO CANADA BY THANKSGIVING DAY FOLLOWED BY A STRONG
COLD FRONT. PRECIPITATION WILL INCREASE OVER THE FORECAST AREA
THURSDAY NIGHT WITH SNOW LEVELS AROUND 4500-5000 FEET EARLY IN THE
EVENING LOWERING TO NEAR 2500-3000 FEET THURSDAY NIGHT AND FRIDAY
MORNING. BELIEVE THERE WILL BE SNOW ACCUMULATIONS IN THE MOUNTAINS
WITH VERY LIGHT AMOUNTS BELOW 3500 FEET BUT I DO NOT ANTICIPATE ANY
AMOUNTS MEETING ADVISORY AT THIS TIME. THE BIG CONCERN WILL BE
WINDS. THE TRACK AND STRENGTH OF THE SYSTEM IS COMPARABLE TO THE
VERY WINDY CONDITIONS THAT WERE OBSERVED LAST SUNDAY. A WIND
ADVISORY IS CURRENTLY IN EFFECT FOR THE SOUTHERN PORTION OF THE
GRANDE RONDE VALLEY THROUGH WEDNESDAY AFTERNOON...BUT THE ADVISORY
MAY BE EXTENDED THROUGH THANKSGIVING FOR THE GRANDE RONDE VALLEY AND
OTHER LOCATIONS IN OUR FORECAST AREA. JOHNSON
LONG TERM...FRIDAY NIGHT THROUGH TUESDAY. A DEPARTING DISTURBANCE
WILL MOVE ACROSS THE REGION FRIDAY NIGHT BRINGING COOLER TEMPS ALONG
WITH CLOUDS AND SHOWERS TO THE AREA MOUNTAINS. THEN A WEAK RIDGE
IMPROVES THE REGIONS WEATHER SOMEWHAT SATURDAY BUT MOISTURE AGAIN IS
EXPECTED TO LINGER IN THE AREA MOUNTAINS WHERE SOME SHOWERS SHUD
CONTINUE. THEN ANOTHER STORM IS FORECAST TO TRACK THROUGH WA/OR
SATURDAY NIGHT WITH WARMER TEMPS AND THE CLOUDS AND SHOWERS SHOULD
PERSIST. THE STORM MOVES EAST AND HIGH PRESSURE SHOULD BUILD INTO
THE TWO STATE AREA SUNDAY AND REMAIN INTO THE BEGINNING OF NEXT
WEEK. PATCHY FOG MAY DEVELOP OVER THE COLUMBIA BASIN SUNDAY NIGHT
AND MONDAY NIGHT.
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 35 48 36 51 / 0 0 0 10
ALW 37 46 36 51 / 0 0 10 10
PSC 33 48 36 46 / 0 0 10 10
YKM 31 45 34 45 / 0 0 30 30
HRI 32 48 34 49 / 0 0 0 10
ELN 34 45 32 43 / 10 10 40 40
RDM 29 51 30 50 / 0 0 0 10
LGD 30 44 31 42 / 0 0 0 10
GCD 32 51 28 49 / 0 0 0 10
DLS 35 51 38 48 / 0 0 10 30
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...WIND ADVISORY UNTIL 3 PM PST WEDNESDAY FOR ORZ049.
WA...NONE.
&&
THREAT INDEX
WEDNESDAY : GREEN
THURSDAY : GREEN
FRIDAY : YELLOW
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
83/97/83
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