Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 271130 AAA
AFDPDT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
330 AM PST SAT DEC 27 2014

UPDATED AVIATION DISCUSSION

.SHORT TERM...TODAY THROUGH SUNDAY...A STORM SYSTEM MOVING SOUTHEAST
ALONG THE BRITISH COLUMBIA COAST WILL MOVE THROUGH THE REGION TODAY
AND TONIGHT. THIS SYSTEM WILL BRING PRECIP TO MUCH OF THE AREA WITH
THE HEAVIEST AMOUNTS ALONG THE CASCADE EAST SLOPES, OVER THE BLUE
MOUNTAINS, ACROSS THE GRANDE RONDE VALLEY AND IN WALLOWA COUNTY.
SNOW LEVELS IN THESE AREAS WILL REMAIN LOW, ONLY RISING TO NEAR 3200
FEET IN THE BLUE MOUNTAINS, BRIEFLY TO NEAR 3000 FEET IN THE GRANDE
RONDE VALLEY AND WALLOWA COUNTY, AND ONLY TO NEAR 2500 FEET ALONG
THE WASHINGTON CASCADE EAST SLOPES. SNOW LEVELS IN CENTRAL OREGON
WILL RISE TO BETWEEN 3000 AND 3500 FEET. THESE HIGHEST SNOW LEVELS
WILL OCCUR ROUGHLY FROM MID AFTERNOON INTO MID EVENING. OVERALL
STILL EXPECT DECENT SNOW FALL IN THE AREAS WHERE PRECIP IS HEAVIEST
AND OVER OTHER HIGHER TERRAIN AREAS. THUS WILL CONTINUE THE CURRENT
WINTER STORM WARNINGS AND WINTER WEATHER ADVISORIES. COLDER AIR WILL
FILTER INTO THE REGION LATE TONIGHT AND ON SUNDAY. THUS SNOW LEVELS
WILL FALL LATE TONIGHT. DAYTIME HEATING MAY LIFT THE SNOW LEVELS TO
BETWEEN 1500 AND 2000 FEET SUNDAY AFTERNOON. PRECIP AMOUNTS WILL
TAIL OFF LATE TONIGHT THROUGH THE DAY SUNDAY AND ONLY EXPECT LIGHT
AMOUNTS OF ADDITIONAL SNOW. WINDS WILL BE LOCALLY BREEZY THIS
AFTERNOON INTO TONIGHT AS THE MAIN SURFACE LOW MOVES THROUGH
NORTHERN AND NORTHEASTERN WASHINGTON. 90

.LONG TERM...SUNDAY NIGHT THROUGH SATURDAY...ANOTHER LOW WILL MOVE
DOWN FROM THE NORTH ON SUNDAY NIGHT AND MONDAY WITH MUCH COOLER AIR
AND WIDESPREAD SHOWERS. SNOW LEVELS WILL FALL DURING THIS PERIOD TO
NEAR ZERO BY MONDAY MORNING. THEREFORE...EVEN THE LOWEST ELEVATIONS
COULD SEE SOME LIGHT SNOW ACCUMULATIONS. AT THIS TIME 1 TO 2 INCHES
OF SNOW ARE FORECAST FOR THE LOWER COLUMBIA BASIN AND SURROUNDING
VALLEYS AND FOOTHILLS. A MUCH COLDER AND DRIER NORTHERLY FLOW WILL
THEN  FOLLOW TUESDAY THROUGH THURSDAY. THE COLDEST DAY WILL BE
TUESDAY WITH DAYTIME HIGH TEMPERATURES ONLY IN THE TEENS AND 20S AND
OVERNIGHT LOWS IN THE SINGLE DIGITS TO BELOW ZERO. TEMPERATURES WILL
THEN VERY GRADUALLY WARM WEDNESDAY THROUGH SATURDAY. MODELS SHOW THE
PACIFIC RIDGE WEAKENING ON FRIDAY AND A SPLIT FLOW DEVELOPING WITH
MOISTURE STREAMING BOTH TO THE NORTHEAST AND WEST OF THE LOCAL AREA.
THIS SOLUTION WOULD KEEP THE CWA MOSTLY DRY...BUT HAVE KEPT SOME LOW
PRECIPITATION CHANCES IN THE FORECAST TO ACCOUNT FOR UNCERTAINTY.
SATURDAY HAS BETTER PRECIPITATION CHANCES...ESPECIALLY OVER THE
WASHINGTON CASCADES AND THE NORTHERN BLUES. ALTHOUGH TEMPERATURES
MAY GET INTO THE MID 30S ON SATURDAY...ANY PRECIPITATION WILL LIKELY
FALL AS MOSTLY SNOW.  COBB

&&

.AVIATION...12Z TAFS...MAINLY VFR CONDITIONS WILL PREVAIL. MID AND
HIGH CLOUDS WILL INCREASE AS A STORM SYSTEM ARRIVES TODAY.
PRECIPITATION WILL ARRIVE THIS MORNING...AFFECTING ALL TAF SITES BY
AFTERNOON WITH MVFR OR EVEN IFR CONDITIONS IN RAIN. SNOW SHOWERS MAY
BE POSSIBLE BY SUNDAY MORNING AT KRDM AND KBDN. WINDS WILL BECOME
BREEZY THIS AFTERNOON WITH WIND SPEEDS MOSTLY 10 TO 20 KTS.  82

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  43  31  39  25 /  80  60  50  30
ALW  44  34  38  26 /  80  80  40  30
PSC  43  33  43  29 /  50  30  20  30
YKM  38  27  38  26 /  40  30  20  40
HRI  44  34  43  30 /  60  30  20  30
ELN  36  27  36  27 /  50  30  20  50
RDM  44  27  38  20 /  40  30  20  30
LGD  35  31  35  20 /  90  90  80  40
GCD  39  28  36  20 /  70  80  60  40
DLS  47  35  45  31 /  60  40  30  40

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO 10 AM PST
     SUNDAY ORZ505-506.

     WINTER STORM WARNING FROM 7 AM THIS MORNING TO 10 AM PST SUNDAY
     ORZ049-050-502-503.

     WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO 10 AM PST
     SUNDAY ORZ509.

WA...WINTER STORM WARNING FROM 7 AM THIS MORNING TO 10 AM PST SUNDAY
     WAZ030.

     WINTER STORM WARNING UNTIL 4 AM PST SUNDAY WAZ520.

&&

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

$$

90/82/82





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