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fxus66 kpdt 232201 

Area forecast discussion
National Weather Service Pendleton or
201 PM PST Tue Jan 23 2018

Short term...tonight through Thursday. Larger upper level low off
the British Columbia coast with several well defined short waves rotating
through. A deep plume of moisture currently over the Pacific
northwest. Steady precipitation has been occurring over the
Cascades today and has spread east across the forecast area this
afternoon. Expect rain and higher elevation snow to continue
overnight into Wednesday...mainly focused along the approaching
frontal boundary. Pattern supports heavy precipitation over the
Cascades the next 24 hours. Southwest flow with warm advection
will gradually increase the snow levels overnight into Wednesday
morning. However the Washington Cascades and east slopes will be
slower to warm and will likely see the highest snow accumulations.
The upper low will push a cold front through the region late Wed
and snow levels will decrease for all locations. Rain and snow
will taper off Wed night with gradual clearing and much colder
temperatures. The weakening low will move through the area Thursday
with additional rain and mountain snow. 94

Long term...Thursday night through Monday. The wet and occasionally
windy conditions will continue through the long term period. A
series of frontal systems will bring areawide rain and snow each
day. Snow levels Thursday night through Friday night will be around
1000-2000 feet msl, so that most of the forecast area will have
snow. Snow levels will then increase with a moist warm front over
the weekend. Models are in good agreement that the warm front will
bring widespread precipitation Saturday, then precipitation tapers
off from the south Saturday night as the front travels north into
b.C. A secondary warm front will follow Saturday night, primarily
affecting Washington and far northern Oregon. By Sunday, snow
levels are forecast to range from 5000-6000 feet. The
GFS/ECMWF/Canadian also agree on a strong but fast-moving cold front
late Monday and Monday night that could bring snow levels back down
to the Columbia Basin floor as well as bring gusty winds to the
area. Wister


Aviation...18z tafs (previous discussion)...VFR conditions are
forecast for all taf sites with the exception of kdls and kykm where
MVFR/IFR conditions are expected with light rain. Kdls has been
fluctuating between IFR and VFR, and believe this will continue
through the day. Kykm will likely see ceilings and visibility lower to MVFR as
light rain mixed with snow develops in the next hour or two. Other
taf sites will have ceilings lower to around 3500-6000 feet above ground level in light
rain. Winds will be 15 knots or less, but gusts to 25 knots are
possible at kpdt, kalw, krdm and kbdn...mainly tonight. Wister


Preliminary point temps/pops...
PDT 41 52 32 44 / 90 70 80 40
alw 42 51 33 45 / 90 70 80 50
psc 40 51 31 47 / 90 60 70 40
ykm 35 46 27 41 / 90 60 60 50
hri 40 53 32 47 / 80 70 70 40
eln 32 42 25 37 / 90 60 60 50
rdm 36 46 24 41 / 80 60 60 50
lgd 36 44 26 40 / 70 60 80 40
gcd 35 45 24 38 / 50 60 70 40
dls 39 48 31 44 / 80 60 60 70


PDT watches/warnings/advisories...
or...Winter Weather Advisory until 10 am PST Wednesday for orz502.

Washington...Winter Weather Advisory until 10 am PST Wednesday for waz030.

Winter Weather Advisory until 10 PM PST Wednesday for waz520.

Winter Storm Warning until 10 PM PST Wednesday for waz520.

Winter Weather Advisory until 10 PM PST this evening for waz026.

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