Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 130657 AAA
AFDPDT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
1057 PM PST FRI FEB 12 2016

UPDATED AVIATION DISCUSSION

.SHORT TERM...A COLD FRONT IS MOVING THROUGH THE FORECAST AREA
THIS EVENING BRINGING NUMEROUS RAIN SHOWERS TO SOUTHEAST
WASHINGTON AND NORTHEAST OREGON AND ISOLATED THUNDERSTORMS OVER
THE BLUE MOUNTAINS.

I HAVE UPDATED THE FORECAST FOR THIS EVENING TO INTRODUCE
ISOLATED THUNDERSTORMS ACROSS THE BLUE MOUNTAINS AND IN UNION AND
WALLOWA COUNTIES. SOUTHERN GRANT COUNTY HAS A SLIGHT CHANCE OF A
THUNDERSTORMS THIS EVENING.  POLAN

&&

.AVIATION...06Z TAFS...A COLD FRONT IS STILL MOVING THROUGH THE
FOOTHILLS OF THE NORTHERN BLUE MOUNTAINS AND IS TRIGGERING SHOWERS
FROM KPDT TO KALW TO DAYTON LATE THIS EVENING. AS SUCH BROKEN TO
OVERCAST MID LEVEL CLOUDS WILL PERSIST AT KPDT AND KALW THROUGH MOST
OF OVERNIGHT. SHOWERS AT KPDT AND KALW SHOULD TAPER OFF AND END BY
AROUND 13TH/09Z. MAINLY VFR CONDITIONS ARE EXPECTED FOR THE NEXT 24
HOURS, EXCEPT AT KYKM WHERE FOG AND LOW CIGS DUE TO STRATUS CLOUD
DECK ARE EXPECTED TO YIELD LIFR/IFR CONDITIONS THROUGH TONIGHT AND
PROBABLY FOR A FEW HOURS AFTER DAYBREAK BEFORE THE FOG AND LOW
CEILING DISSIPATES AT KYKM.

SKIES WILL PARTIALLY CLEAR OVERNIGHT AND WITH RECENT RAIN, FOG MAY
DEVELOP OVERNIGHT AT COLUMBIA BASIN TAF SITES. DID NOT ADD TO TAFS
BEYOND A MENTION OF 6SM WITH BR AS AN INCREASE IN WINDS TO AROUND 5-
10 KTS AT MOST TAF SITES IS EXPECTED TO KEEP FOG AT A MINIMUM. CLOUD
COVER WILL BEGIN TO INCREASE AGAIN AFTER 18Z TOMORROW WITH MID LEVEL
CLOUD BASES LOWERING THROUGH THE AFTERNOON AS ANOTHER DISTURBANCE
APPROACHES THE AREA. SHOWERS WILL GENERALLY HOLD OFF UNTIL AFTER
14TH/00Z. HOWEVER, SHOWERS ARE POSSIBLE AT KDLS AFTER 22Z. WINDS
WILL GENERALLY BE UNDER 5-10 KTS THROUGH 13TH/ 20Z AND THEN INCREASE
TO 10-15 KTS SATURDAY AFTERNOON.  POLAN

&&

.PREVIOUS DISCUSSION... /ISSUED 401 PM PST FRI FEB 12 2016/

SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT...THE LATEST PACIFIC
SYSTEM CONTINUES TO MOVE INTO AND THROUGH THE PACIFIC NORTHWEST THIS
AFTERNOON. THE SYSTEM`S COLD FRONT IS NOW APPROACHING THE CASCADE
CREST. EXPECT THIS FRONT TO SWING EAST OF THE CREST AND ACROSS
EASTERN WASHINGTON AND OREGON LATE THIS AFTERNOON AND THIS EVENING.
WILL SEE VARYING AMOUNTS OF SHOWERS WITH THIS FRONT. THE BEST
CHANCES OF SHOWERS WILL BE NEAR THE CASCADE CREST, ALONG THE BLUE
MOUNTAIN FOOTHILLS, AND FROM THE BLUE MOUNTAINS EAST TO WALLOWA
COUNTY THIS EVENING. WEST-NORTHWEST FLOW ALOFT WILL KEEP ISOLATED TO
SCATTERED SHOWERS GOING IN THESE SAME AREAS OVERNIGHT INTO SATURDAY.
OTHER AREAS WILL DRY OUT OVERNIGHT. SNOW LEVELS WILL LOWER BEHIND
THE FRONT TO BETWEEN 3500 AND 4500 FEET. SNOW AMOUNTS ABOVE THESE
LEVELS WILL LIGHT, 2 INCHES OR LESS. WINDS WILL ALSO GRADUALLY
INCREASE ACROSS PORTIONS OF THE BASIN TONIGHT BEGINNING THE PROCESS
OF MIXING OUT SOME OF THE STAGNANT AIR. THUS MOST LOCATIONS SHOULD
SEE THE AIR STAGNATION ADVISORIES EXPIRE SATURDAY MORNING, THOUGH A
FEW LOCATIONS COULD SEE ADVISORIES DROPPED TONIGHT. CAN EXPECT A
PERIOD OF WARM AIR ADVECTION ALOFT SATURDAY NIGHT THROUGH SUNDAY
NIGHT. AT THE SAME TIME, DISTURBANCES WILL MOVE ACROSS THE AREA.
THUS WILL SEE PERIODS OF RAIN SATURDAY NIGHT THROUGH SUNDAY NIGHT.
SNOW LEVELS WILL GRADUALLY RISE LIMITING SNOW FALL. WINDS WILL ALSO
BECOME BREEZY BY SUNDAY IN MANY AREAS. 90

LONG TERM...MONDAY THROUGH FRIDAY...INITIALLY THE AREA WILL BE ON
THE EASTERN SIDE OF A RIDGE OF HIGH PRESSURE CENTERED IN THE EASTERN
PACIFIC. A DISTURBANCE WILL BE LEAVING THE AREA MONDAY WITH A SLIGHT
CHANCE OF RAIN SHOWERS LINGERING IN THE MOUNTAINS. THE RIDGE WILL
STRENGTHEN THROUGH TUESDAY AND WILL STEER DISTURBANCES TO OUR NORTH
SO MONDAY NIGHT THROUGH TUESDAY NIGHT WILL BE GENERALLY DRY AND
WARM. BY TUESDAY NIGHT AN UPPER LOW WILL BE DROPPING SOUTH OUT OF
THE GULF OF ALASKA AND WILL BE PUSHING THE RIDGE OFF TO THE EAST.
MODELS CONTINUE TO DIFFER AS TO THE HANDLING OF THE LOW. THE GFS
KEEPS THE LOW OFF THE NORTHERN BRITISH COLUMBIA COAST AND SENDS A
TROUGH THROUGH THE AREA WEDNESDAY NIGHT WHILE THE ECMWF BRINGS THE
LOW AND TROUGH TO THE SOUTHERN OREGON COAST AND THROUGH THE AREA
WEDNESDAY NIGHT THROUGH THURSDAY NIGHT. HAVE TAKEN A MIDDLE GROUND
AND HAVE A CHANCE OF RAIN WEDNESDAY THROUGH THURSDAY WITH SNOW
LEVELS AT 5000-6000 FEET. THURSDAY NIGHT HAVE THE SHOWERS TAPERING
OFF AND ANOTHER RIDGE DEVELOPING ALONG THE COAST. THE GFS KEEPS THE
RIDGE OVER THE AREA WITH A LARGE TROUGH BEING HELD OFFSHORE ON
FRIDAY WHILE THE ECMWF BRINGS THE RIDGE THROUGH THE AREA RAPIDLY
FRIDAY MORNING AND THEN BRINGS A FRONT TO THE CASCADES IN THE
AFTERNOON. HAVE LEANED TOWARDS THE ECMWF AND HAVE A SLIGHT CHANCE OF
RAIN IN THE LOWER ELEVATIONS AND A CHANCE OF RAIN WITH SNOW ABOVE
5000 FEET IN THE MOUNTAINS. TEMPERATURES WILL BE IN THE UPPER 50S TO
MID 60S WITH 50S IN THE MOUNTAINS MONDAY AND TUESDAY. WEDNESDAY
THROUGH FRIDAY WILL BE IN THE 50S WITH 40S AND LOWER 50S IN THE
MOUNTAINS. PERRY

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  39  54  42  56 /  70  10  80  60
ALW  42  54  45  57 /  70  20  80  60
PSC  38  56  41  58 /  60  10  60  20
YKM  34  50  34  54 /  20  10  30  20
HRI  39  56  40  58 /  60  10  60  30
ELN  33  46  36  49 /  20  20  50  30
RDM  30  51  38  55 /  20  10  40  40
LGD  34  51  38  51 /  50  20  80  70
GCD  33  50  36  53 /  20  10  60  60
DLS  40  53  40  54 /  30  20  50  50

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...AIR STAGNATION ADVISORY UNTIL 10 AM PST SATURDAY FOR ORZ041-044-
     050-505-507-508-510.

WA...AIR STAGNATION ADVISORY UNTIL 10 AM PST SATURDAY FOR WAZ024-
     026>029-520-521.

&&

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

$$

99/90/83



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