Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 181025
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
225 AM PST THU DEC 18 2014

.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...LOCALLY DENSE ALONG THE
FOOTHILLS AND KITTITAS VALLEY...THIS MORNING. A DENSE FOG ADVISORY
IS CURRENTLY IN EFFECT FOR THESE AREAS UNTIL AT LEAST 10 AM THIS
MORNING. 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...PREVIOUS DISCUSSION...06Z TAFS...IFR/LIFR CONDITIONS
WILL PREVAIL AT KPDT AND KALW. MVFR CONDITIONS WILL PREVAIL AT OTHER
TAF SITES WITH OCCASIONAL IFR CIGS UNTIL 18Z. THESE CONDITIONS WILL
CONTINUE INTO THE MORNING HOURS ON THURSDAY WITH SOME IMPROVEMENT
POSSIBLE AFTER 18Z THURSDAY. WINDS WILL BE LIGHT. 76

&&

.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...DENSE FOG ADVISORY UNTIL 10 AM PST THIS MORNING ORZ507-508.

WA...DENSE FOG ADVISORY UNTIL 10 AM PST THIS MORNING WAZ026-029.

     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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