Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 281139 AAA
AFDPDT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
339 AM PST SUN DEC 28 2014

UPDATED AVIATION DISCUSSION

.SHORT TERM...TODAY THROUGH MONDAY...THE SYSTEM THAT AFFECTED THE
REGION SATURDAY AND SATURDAY EVENING CONTINUES TO MOVE EAST AWAY
FROM THE REGION. IN IT`S WAKE, A COOL, MOIST NORTHWEST FLOW REMAINS
OVER THE PACIFIC NORTHWEST THIS MORNING. AS SUCH, EXPECT VARYING
AMOUNTS OF SHOWERS TO PERSIST ACROSS THE REGION TODAY INTO THIS
EVENING. SNOW LEVELS WILL RUN BETWEEN 2000 FEET AND 3000 FEET MSL
TODAY WITH THE HIGHER SNOW LEVELS ACROSS OUR SOUTHERN ZONES. AS SUCH
THE SHOWERS WILL BE LARGELY SNOW EXCEPT AT THE LOWEST ELEVATIONS.
SHOWERS ALONG THE WASHINGTON CASCADE CREST HAVE DECREASED TO
SCATTERED COVERAGE AND SHOULD REMAIN AS SUCH THROUGH TODAY. THESE
SHOWERS WILL NOT VENTURE VERY FAR EAST OF THE CREST, THUS WILL ALLOW
THE CURRENT WINTER STORM WARNING THERE TO EXPIRE AT 4 AM. SHOWERS
CONTINUE TO BE ENHANCED DUE TO UPSLOPE AFFECTS INTO THE BLUE
MOUNTAINS, AND THESE SHOWERS ARE SLOPING OVER INTO THE GRANDE RONDE
VALLEY. THUS WILL CONTINUE THE WARNINGS IN THESE AREAS. AM LESS
CERTAIN AS TO THE AMOUNT OF SNOW SHOWERS THAT WILL BE SEEN THIS
MORNING ACROSS WALLOWA COUNTY, THE JOHN DAY BASIN, THE OCHOCO-JOHN
DAY HIGHLANDS, AND THE OREGON CASCADE EAST SLOPES. FOR NOW WILL
LEAVE THE HIGHLIGHTS IN THESE AREAS UP. WILL WATCH THESE AREAS FOR A
WHILE AND MAY RECONSIDER THE POSSIBILITY OF CANCELLING. AN ARCTIC
FRONT IS STILL EXPECTED TO MOVE INTO AND THROUGH THE REGION LATE
TONIGHT AND MONDAY. THUS WILL CONTINUE TO INDICATE GRADUALLY
LOWERING SNOW LEVELS, WITH SNOW LEVELS MOSTLY TO THE BASIN FLOOR BY
LATE MORNING MONDAY. AT THIS TIME SNOW AMOUNTS WITH THIS FRONT LOOK
TO BE LIGHT, THOUGH COULD PUSH LOW END ADVISORIES IN THE OREGON BLUE
MOUNTAIN FOOTHILLS ON MONDAY. 90

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY...THE LOW WILL MOVE SOUTH
OF THE AREA ON MONDAY NIGHT BUT LINGERING SNOW SHOWERS CAN BE
EXPECTED OVER OREGON AND SOUTHERN WASHINGTON. AN ADDITIONAL 1 TO 2
INCHES OF SNOW WILL BE POSSIBLE OVER THE MOUNTAINS OF NORTHEAST
OREGON WITH LESS THAN AN INCH EXPECTED ELSEWHERE. 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 THROUGH THE REST OF
THE WEEK. MODELS SHOW THE PACIFIC RIDGE WEAKENING ON FRIDAY AS
TROUGHING OVER THE MIDDLE OF THE CONTINENT PUSHES INTO THE REGION.
THERE ARE MODEL DIFFERENCES WITH THE GFS BEING MUCH MORE
AGGRESSIVE...BUT THE ECMWF DOES AGREE THAT THERE WILL BE SOME
PRECIPITATION DURING THIS PERIOD. THE MOST LIKELY SCENARIO IS
MOUNTAIN SNOW FRIDAY AND SATURDAY...WITH LESSER RAIN AND SNOW
CHANCES AT THE LOWER ELEVATIONS. THERE IS ALSO A QUESTION OF HOW
MUCH WARMING WILL OCCUR. IF THE ECMWF IS CORRECT IN KEEPING THE
STRONGER RIDGE ALONG THE COAST...DAYTIME TEMPERATURES COULD WARM
INTO THE MID TO UPPER 30S AND THE AREA WOULD ALSO STAY MUCH DRIER
GOING INTO SUNDAY. THE WEEKEND FORECAST WILL CONTINUE TO BE
EVALUATED OVER THE NEXT SEVERAL DAYS.  COBB

&&

.AVIATION...12Z TAFS...MOSTLY VFR CONDITIONS WILL PREVAIL.
HOWEVER...POSSIBLE RAIN AT KALW AND SNOW SHOWERS AT KRDM AND KBDN
TODAY COULD LOWER CONDITIONS TO MVFR. THEN CONDITIONS COULD WORSEN
AT THE REMAINING SITES SUNDAY NIGHT IN RAIN AND SNOW SHOWERS AND/OR
LOWER CEILINGS. WINDS WILL BE 5 TO 15 KTS AND MAINLY FROM THE
WEST-SOUTHWEST TODAY...THEN SHIFT MORE NORTHERLY ON MONDAY.  82

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  42  28  30  10 /  40  60  60  30
ALW  42  30  32  12 /  40  60  50  20
PSC  45  31  34  15 /  20  40  40  20
YKM  40  29  32  11 /  20  50  50  10
HRI  46  32  34  16 /  20  60  60  20
ELN  40  24  28  10 /  20  60  60  10
RDM  40  22  31   3 /  20  40  50  20
LGD  37  25  30   8 /  80  60  60  30
GCD  36  26  31   3 /  60  50  50  30
DLS  46  34  37  15 /  20  60  60  20

&&

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

     WINTER STORM WARNING UNTIL 10 AM PST THIS MORNING
     ORZ049-050-502-503.

     WINTER WEATHER ADVISORY UNTIL 10 AM PST THIS MORNING ORZ509.

WA...WINTER STORM WARNING UNTIL 10 AM PST THIS MORNING WAZ030.

     WINTER STORM WARNING UNTIL 4 AM PST EARLY THIS MORNING WAZ520.

&&

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

$$

90/82/82






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