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FXUS66 KPDT 210413

Area Forecast Discussion
National Weather Service Pendleton OR
813 PM PST Fri Jan 20 2017

.UPDATE...Precipitation is rotating around an offshore low
tonight. Radar and observations show precipitation has persisted
even behind the front, particularly in the Yakima and Kittitas
Valleys. With temperatures hovering around freezing a mixture of
rain, sleet and snow is possible from north central OR to the
Kittitas Valley. Will continue existing Winter Weather Advisories.


.PREV DISCUSSION... /issued 320 PM PST Fri Jan 20 2017/ 

SHORT TERM...Tonight through Saturday night...A Pacific frontal
boundary continues to swing north and northeast across the Interior
Northwest this afternoon. This front has produced decent precip,
mainly in the form of snow, over Wasco and Sherman counties in
Oregon and in Klickitat county in Washington. Some light rain, sleet
and freezing rain has mixed in at a few locations. Snow also
continues over portions of Grant county. Precip seen on radar over
the Columbia Lower Basin and Blue Mountain Foothills has had a tough
time reaching the ground due to down slope affects associated with
southeast winds flowing over the Blue mountains. Still expect
upslope enhancement of precip over Yakima and Kittitas counties this
evening, and will continue the winter weather advisories in the
Yakima and Kittitas valley zones. For now, will also continue the
other winter weather advisories in the Gorge, the Simcoe Highlands
and North-Central Oregon, though precip may wind down in these area
earlier than originally thought. Precip chances will gradually taper
off areawide overnight as the current front moves north of the area.
A weaker system still looks to move through the area Saturday
afternoon and evening. This system will again bring a mix of snow
and rain. Spotty freezing rain can not be completely ruled out, but
will not try to pin point where this precip type may occur as will
have to see how surface temps evolve Saturday. Precip with this wave
will decrease late Saturday evening, but central Oregon will begin
to see snow associated with yet another Pacific system early Sunday

Expect locally windy conditions to persist off and on through this
period along the base of the Blue mountains in Umatilla county and
at the south end of the Grande Ronde valley. 90 

LONG TERM...Sunday through Friday...An offshore upper low will push
a frontal boundary through the area Sunday with lower elevation rain
and higher elevation snow. The low will move slowly south into
California Monday. Skies will remain cloudy with a chance of rain
and mountain snow. An upper ridge starts to build offshore Tue with
northerly flow over the region. Expect gradual clearing during the
day. Snow showers over the northeast Oregon mountains. The ridge
will build over the area Wed through Fri. Skies will be partly
cloudy. Light low level winds and inversion developing will result
in areas of freezing fog in the Columbia basin along with possible
air stagnation issues. High temperatures through the extended period
mostly in the 20s and 30s. 94 

AVIATION...00Z TAFS. Frontal boundary moving through the area this
evening followed by upper level trough tonight into Saturday. Mixed
rain and snow showers likely. Ceilings will be bkn-ovc 040-080. Some
low clouds and fog in the Columbia basin could bring lower ceilings
and visibility especially for psc ykm dls. Winds 5-15kt.  94


PDT  30  40  30  39 /  50  10  20  60 
ALW  31  40  33  41 /  40  20  20  60 
PSC  30  37  29  38 /  50  20  20  60 
YKM  27  36  29  36 /  80  30  30  70 
HRI  28  37  28  37 /  60  10  20  60 
ELN  28  35  28  34 /  80  30  40  80 
RDM  26  40  28  38 /  30  50  50  60 
LGD  27  34  30  35 /  40  20  30  60 
GCD  27  40  29  38 /  60  30  20  70 
DLS  30  36  30  38 /  80  60  30  80 


OR...Winter Weather Advisory until 4 AM PST Saturday for ORZ041-510.

WA...Winter Weather Advisory until 4 AM PST Saturday for WAZ024-026-


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