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[Printable]
099
FXUS66 KPDT 181150 AAB
AFDPDT

AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE PENDLETON OR
350 AM PST THU DEC 18 2014

CANCELLED THE DENSE FOG ADVISORY

.SHORT TERM...TODAY THROUGH SATURDAY...A WEAK WEATHER DISTURBANCE IS
PULLING OUT OF THE AREA THIS MORNING WITH A WEAK UPPER RIDGE TO
BUILD OVER THE REGION TODAY. THIS WILL BRING A TEMPORARY BREAK IN
THE PRECIPITATION TO THE CWA FOR TODAY. WINDS WILL REMAIN LIGHT AND
STAGNANT AIR CONDITIONS WITH PATCHY FOG. AN AIR STAGNATION ADVISORY
REMAINS IN EFFECT TODAY INTO MOST OF FRIDAY FOR THE LOWER COLUMBIA
BASIN OF WASHINGTON AND THE YAKIMA/KITTITAS VALLEYS. THE NEXT
WEATHER SYSTEM WILL BEGIN TO PUSH MOISTURE INTO THE CWA BEGINNING
TONIGHT WITH RAIN AND HIGHER MOUNTAIN SNOW DEVELOPING FROM WEST TO
EAST OVERNIGHT. BY FRIDAY MORNING THE ENTIRE CWA WILL BE IN THE
LIKELY CATEGORY FOR RAIN AND HIGHER MOUNTAIN SNOW. THIS SYSTEM WILL
BE WETTER THAN THE ONE THAT JUST MOVED THROUGH THE CWA AND EXPECT
POSSIBLE HEAVY RAIN IN THE HIGHER ELEVATIONS. SNOW LEVELS SHOULD BE
HIGH ENOUGH TO NEGATE THE NEED OF ANY WINTER WEATHER HIGHLIGHTS FOR
LATE TONIGHT OR FRIDAY. STILL COULD SEE SEVERAL INCHES IN THE HIGHER
MOUNTAINS IN SUCH AREAS AS MEACHAM AND TOLLGATE AND THE CASCADE EAST
SLOPES. THERE WILL BE ANOTHER TEMPORARY BREAK IN THE ACTION ON
FRIDAY NIGHT AND THEN A STRONGER SYSTEM WILL GET READY TO MOVE IN ON
SATURDAY. THE BRUNT OF THIS NEXT SYSTEM WILL HAVE THE GREATEST
IMPACTS IN THE EXTENDED PERIOD...I.E. SATURDAY NIGHT ONWARD. WILL
EXPECT INCREASING RAIN AND ALSO INCREASING WINDS WITH THIS NEXT
SYSTEM BY SATURDAY NIGHT. IN THE MEAN TIME EXPECT CLOUDY SKIES AND
WARMING TEMPERATURES THROUGH THE SHORT TERM PERIOD WITH SNOW LEVELS
INCREASING A LITTLE EACH DAY. 88

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY NIGHT...AN ACTIVE
WEATHER PATTERN IS EXPECTED DURING THE FORECAST PERIOD WITH SEVERAL
STORM SYSTEMS SET TO IMPACT THE AREA.  A 150 KT ZONAL JET IS
EXPECTED TO LINE UP WITH THE PACIFIC NORTHWEST SUNDAY AND MONDAY.
THE RIGHT JET EXIT REGION...SYNONYMOUS WITH SINKING AIR...IS
PRESENTLY PROGGED TO BE OVER THE CWA SUNDAY AND MONDAY WITH THE
POTENTIAL FOR A LEE SIDE TROUGH TO SETUP DOWNWIND OF THE CASCADES.
THEREFORE...CONCERN EXISTS FOR A HIGH WIND EVENT BUT TIMING FROM
RECENT MODEL RUNS HAS DELAYED THE POTENTIAL START OF THE EVENT TO
SUNDAY NIGHT INTO MONDAY.  WILL CONTINUE TO MONITOR OR THE POTENTIAL
FOR HIGH WINDS ACROSS THE CWA AND HAVE CHANGED THE FORECAST TO
INDICATE STRONGEST WIND POTENTIAL INTO MIDDAY SUNDAY INTO EARLY
MONDAY TIMEFRAME.  THE OTHER ITEM OF NOTE DURING THE UPCOMING
WEEKEND IS THE POTENTIAL FOR A STEADY STREAM OF MOISTURE INTO THE
AREA WITH RAINFALL SATURDAY NIGHT THRU MONDAY THAT CAN BE HEAVY AT
TIMES.  QPF TOTALS COULD BE IN EXCESS OF 2 INCHES IN THE MOUNTAINS
WITH BETWEEN A QUARTER TO HALF AN INCH IN LOW LYING AREAS.  GIVEN
THE STRONG WINDS AND A WARM FRONT EXPECTED TO MOVE IN
SUNDAY...TEMPERATURES WILL RISE INTO THE MID 40S TO LOWER 50S IN THE
COLUMBIA BASIN AND UPPER 30S TO MID 40S ALONG THE HIGHER
ELEVATIONS.  THIS WILL TRANSLATE TO A MOSTLY RAIN PRECIPITATION
EVENT...THOUGH SNOW MAY STILL FALL ALONG THE HIGHEST MOUNTAIN PEAKS.

A LONGWAVE RIDGE WILL SETUP OFF THE PACIFIC COAST MONDAY NIGHT
BRINGING A NORTHWEST FLOW TO THE AREA.  SHORTWAVE TROUGHS WILL STILL
RIDE OVER THE RIDGE INTO THE REGION BRINGING A CHANCE OF
PRECIPITATION FAVORING THE HIGHER ELEVATIONS THROUGH EARLY
WEDNESDAY.  A TROUGH ORIGINATING FROM THE GULF OF ALASKA AND BRITISH
COLUMBIA IS PROGGED TO MOVE SOUTHEAST INTO OUR REGION WEDNESDAY WITH
A SHOT OF ARCTIC AIR EXPECTED.  THIS WILL DROP TEMPERATURES 10
DEGREES ON WEDNESDAY...CHRISTMAS EVE...WITH THE POSSIBILITY OF SNOW
LEVELS DROPPING DOWN TO THE COLUMBIA BASIN FLOOR.  BIEDA

&&

.AVIATION...12Z TAFS...IFR/MVFR CONDITIONS WILL PREVAIL AT
KDLS...KPDT AND KALW DUE TO LOW STRATUS AND FOG WITH AT WORST MVFR
CONDITIONS AT ALL OTHER TAF SITES DUE TO LOW CLOUDS THRU 18Z.
AFTERWARDS...CONDITIONS SHOULD IMPROVE DURING THE DAY BUT AN
APPROACHING WEATHER SYSTEM WILL START TO SPREAD RAIN AFT 19/03Z TO
ALL TAF SITES.  CONDITIONS WILL DETERIORATE AFT 19/03Z DOWN TO
IFR/MVFR...WITH OCNL LIFR UNDER HEAVIER RAIN ACTIVITY.  WINDS WILL
BE AOB 10 KTS THROUGHOUT THE TAF PERIOD.  BIEDA

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  41  33  43  35 /  10  60  70  20
ALW  42  35  44  37 /  10  60  80  20
PSC  44  34  46  36 /  10  60  70  10
YKM  42  33  44  32 /  10  70  60  10
HRI  43  33  45  36 /  10  60  70  20
ELN  41  33  43  32 /  10  70  60  10
RDM  45  32  47  31 /  10  60  60  20
LGD  47  35  49  31 /  20  40  80  20
GCD  44  32  46  35 /  20  40  80  20
DLS  46  37  48  39 /  10  70  70  30

&&

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

WA...AIR STAGNATION ADVISORY UNTIL 10 AM PST FRIDAY WAZ026>028.

&&

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

$$

88/98/76







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