Heavy Snow in Washington, December 13, 2015

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
403 AM PST SUN DEC 13 2015

UPDATED SHORT TERM AND AVIATION DISCUSSIONS
UPDATED WATCHES/WARNINGS/ADVISORIES SECTION

.SHORT TERM...TODAY THROUGH MONDAY NIGHT...THE LATEST PACIFIC SYSTEM
CONTINUES TO PUSH THROUGH THE REGION EARLY THIS MORNING. THE
SYSTEM'S COLD FRONT EXTENDS ROUGHLY FROM NORTHERN IDAHO ACROSS THE
COLUMBIA BASIN TO WEST-CENTRAL OREGON. THE MAIN ENERGY AND HEAVIEST
PRECIP IS MOVING THROUGH WEST-CENTRAL, SOUTHWEST, CENTRAL AND SOUTH-
CENTRAL OREGON AT THIS MOMENT. ANOTHER WAVE ALONG THE FRONT HAS
INCREASED PRECIP OVER PORTIONS OF NORTHEAST OREGON AS WELL. THUS THE
CURRENT WINTER STORM WARNINGS LOOK GOOD, THOUGH SNOW LEVELS IN
WALLOWA COUNTY ARE CURRENTLY RUNNING NEAR 4000 FEET. PRECIP HAS
SHIFTED TO SHOWERS ACROSS THE WASHINGTON CASCADE EAST SLOPES, AND
ARE MAINLY OCCURRING NEAR THE CREST. FOR NOW WILL LEAVE THE WARNING
IN THIS AREA UP, THOUGH CONDITIONS LOOK TO BE BECOMING MORE
LOCALIZED. SNOW LEVELS HAVE FALLEN TO 2800 TO 3000 FEET IN CENTRAL
OREGON. THUS SNOW ACCUMULATIONS OF AROUND 2 INCHES WILL BE POSSIBLE
IN THE BEND AND REDMOND AREAS. AS SUCH HAVE ISSUED A WINTER WEATHER
ADVISORY FOR SNOW IN THE CENTRAL OREGON ZONE INTO LATE MORNING.
WINDS ALONG THE BLUE MOUNTAIN FOOTHILLS FROM PILOT ROCK TO DAYTON
HAVE SUBSIDED SOME, BUT A FEW LOCATIONS ARE STILL SEEING SUSTAINED
WINDS IN THE 25 TO 30 MPH RANGE. THUS WILL ALLOW THE WIND ADVISORY
IN THIS AREA TO CONTINUE FOR NOW.

THE COLD FRONT SHOULD BE OUT OF THE AREA BY NOON. STILL EXPECT TO
SEE ISOLATED TO NUMEROUS SHOWERS THIS AFTERNOON INTO TONIGHT DUE TO
WESTERLY FLOW. THE BEST CHANCES FOR SHOWERS WILL BE OVER THE HIGHER
TERRAIN. SNOW LEVELS WILL FALL THIS AFTERNOON THROUGH TONIGHT
AREAWIDE. DRIER AIR WILL SLOWLY WORK INTO THE REGION MONDAY AND
MONDAY NIGHT, BUT WEST FLOW AND UPSLOPE AFFECTS WILL KEEP SOME
SNOW SHOWERS GOING OVER THE INTERIOR MOUNTAINS. 90

.LONG TERM...TUESDAY THROUGH SUNDAY...INITIALLY A RIDGE WILL BE
OFFSHORE AND THIS WILL BRING A DRY AND COLD NORTHWEST FLOW OVER THE
AREA. A FAIR AND DRY DAY IS EXPECTED WITH HIGHS IN THE 20S AND 30S.
TUESDAY NIGHT AND WEDNESDAY THE FLOW WILL TURN MORE NORTHWESTERLY AS
A WAVE MOVES INTO THE AREA. THIS WILL BRING AN INCH OR TWO OF SNOW
INTO THE MOUNTAINS THOUGH THE LOWER ELEVATIONS WILL BE MAINLY DRY.
WEDNESDAY NIGHT AND THURSDAY ANOTHER SYSTEM WITH A GENEROUS STREAM
OF MOISTURE WILL MOVE IN FROM THE SOUTH BRINGING A CHANCE OF MAINLY
SNOW WITH SOME RAIN MIXED IN FOR THE COLUMBIA BASIN. THIS WILL BE
FOLLOWED BY A FRONTAL SYSTEM THURSDAY NIGHT AND FRIDAY. THIS SYSTEM
WILL BE WARMER SO EXPECT A CHANCE OF RAIN IN THE LOWER ELEVATIONS
AND A CHANCE OF SNOW ABOVE 5000 FEET IN THE MOUNTAINS. MODELS HAVE
THIS SYSTEM HANG UP ON THE CASCADES (ECMWF) OR THE BLUE MOUNTAINS
(GFS) FRIDAY NIGHT THROUGH SATURDAY NIGHT SO HAVE KEPT A CHANCE OF
LOWER ELEVATION RAIN AND MOUNTAIN SNOW. BY SUNDAY THAT SYSTEM WILL
BE DEPARTING BUT ANOTHER WILL BE APPROACHING THE CASCADES SO HAVE
CONTINUED A CHANCE OF LOWER ELEVATION RAIN AND A CHANCE OF MOUNTAIN
SNOW FOR SUNDAY. TEMPERATURES WILL BE IN THE 20S AND 30S TUESDAY
THROUGH THURSDAY THEN WARM TO THE MID 30S TO LOWER 40S WITH 30S
IN THE MOUNTAINS FOR FRIDAY THROUGH SUNDAY. PERRY

&&

.AVIATION...12Z TAFS...A FRONT WILL CONTINUE TO BRING LIGHT RAIN AND
SNOW SHOWERS TO THE AREA THIS MORNING AFFECTING ALL TAF SITES EXCEPT
KYKM AND KPSC. KBDN AND KRDM ARE HAVING -SN WITH VISIBILITIES DOWN
TO 1SM AND CIGS DOWN TO 100 FEET AGL AT TIMES. WITH SNOW TAPERING
OFF, EXPECT THEY WILL IMPROVE AFTER 15Z AND REACH VFR BY 18Z.
OTHERWISE VFR CONDITIONS ARE EXPECTED TO BE PREVALENT THROUGH LATE
THIS AFTERNOON. AFTER 00Z, A WEAK DISTURBANCE WILL BRING MORE CLOUDS
INTO THE AREA AT VFR LEVELS THOUGH KALW AND KPDT COULD HAVE
OCCASIONAL MVFR CONDITIONS AND LIGHT RAIN SHOWERS. WITH THE FRONT
PASSAGE THIS MORNING, SOUTHWEST WINDS AT KPSC, KPDT AND KALW ARE AT
10 TO 20 KTS WITH GUSTS TO 30 KTS AND WILL SUBSIDE TO BELOW 15 KTS
BY 15Z. WINDS WILL GENERALLY REMAIN BELOW 15 KTS THOUGH KDLS AND
KPDT WILL INCREASE TO 15 TO 20 KTS WITH GUSTS TO 30 KTS AFTER 00Z.
PERRY

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  45  33  41  28 /  70  30  20  10
ALW  46  36  42  32 /  70  30  20  10
PSC  48  35  45  27 /  40  20  10   0
YKM  45  28  43  23 /  30  20  10   0
HRI  48  35  44  28 /  50  20  10   0
ELN  41  29  40  21 /  30  20  10   0
RDM  36  25  35  15 /  80  60  10  10
LGD  40  31  37  23 /  80  50  20  20
GCD  36  25  33  18 /  90  50  20  10
DLS  45  36  44  30 /  60  30  10   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...WINTER STORM WARNING UNTIL 4 AM PST MONDAY FOR ORZ050-502-503-
     506-509.

     WINTER WEATHER ADVISORY UNTIL 10 AM PST THIS MORNING FOR ORZ511.

     WIND ADVISORY UNTIL 3 PM PST THIS AFTERNOON FOR ORZ507.

WA...WINTER STORM WARNING UNTIL 4 AM PST MONDAY FOR WAZ030-520.

     WIND ADVISORY UNTIL 3 PM PST THIS AFTERNOON FOR WAZ029.

&&

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

90/83/83