Wind Advisory 2, NWS Pendleton, OR

Area Forecast Discussion
National Weather Service Pendleton OR
347 AM PST Fri Jan 6 2023

.SHORT TERM...TODAY THROUGH SUNDAY...Current radar and infrared
satellite imagery showing light returns at elevation over the
Washington Cascade crest and the Northern Blue Mountains under
partly to mostly cloudy skies as a weak upper level shortwave
passes through the area this morning. The parent upper level low
pressure will stay offshore and travel north along the British
Columbia coast tonight into Saturday morning. Southwest flow aloft
will continue and strengthen as the low nears the coast, allowing
for light snow showers to redevelop along the Cascades this
afternoon before spilling into the east slopes, Central Oregon,
and through the Lower Columbia Basin as rain late tonight into
Saturday morning as a shortwave spins off the parent low. This
will tighten pressure gradients that orient along the Northern
Blue Mountains, which will also be accompanied by downsloping
winds, to produce windy to breezy conditions peaking late Friday
through Saturday evening. Wind gusts of 55 to 65 mph will be
possible through the foothills of the Northern Blue Mountains,
warranting the issuance of a High Wind Warning that extends from 7
PM PST Friday through 7 PM PST Saturday. Breezy conditions will
also be experienced through the Grande Ronde Valley during this
timeframe with gusts of 45 to 55 mph. This has prompted the
issuance of a Wind Advisory for the aforementioned area from 7PM
PST Friday through 7 PM PST Saturday. Confidence is moderate to
high (60-80%) regarding these wind values, as the NBM 4.1 provides
a 68% chance of wind gusts reaching 55 mph through the Northern
Blue Mountain Foothills and a 74% chance of wind gusts of 47 mph
through the Grande Ronde Valley. ECMWF EFI also highlights
unclimatologically high wind gust values through these areas, with
ensemble members trending increased wind values over the last
several runs.

Overnight showers Friday into Saturday are expected to provide
widespread, light precipitation as snow levels hover between
4000-5000 feet. However, snow levels will still be between
2500-3500 feet along the east slopes of the Washington Cascades
and the Yakima/Kittitas Valleys, allowing for the potential for
snow/rain mix and isolated chances of freezing rain through
Saturday morning. Only a couple hundredths of an inch of rainfall
is anticipated for lower elevations of the Basin with 1 to 3
inches of snowfall over the Cascades, Blues, and Wallowas. Rain
chances taper off through the evening as a transient ridge quickly
slides through the area ahead of another upper level trough that
will approach the coast Sunday morning. This shortwave will follow
a similar path as the earlier wave Friday night into Saturday,
producing another morning of widespread light showers that will
taper off through the day. Another couple hundreths of an inch of
rainfall is expected for lower elevations of the Basin, with an
additional 1-2 inches through the Cascades, Blues, and Wallowas.
Snow levels will be 3000-4000 feet, with the exception of the east
slopes of the Washington Cascades and the Yakima/Kittitas Valleys
which will stay in the 2000-3000 foot range. This will again
provide the potential for isolated chances of freezing rain into
Sunday morning, with minimal accumulations expected. 75

.LONG TERM...MONDAY THROUGH FRIDAY...Deterministic and ensemble
models are in pretty good agreement through the long term period.
Monday the weather pattern will be an upper level trough over the
eastern Pacific and an upper level ridge centered along the Rocky
mountains. This pattern will provide a warm and moist southwest flow
across the region ahead of the the upper level trough moving inland
Tuesday. Monday will be a high POP and high QPF day for parts of the
forecast area with snow levels varying between 2500 to 4500 feet
across the forecast area. Lowest snow levels will be along the east
slopes of the Washington Cascades due to some cold air damming.
Precipitation will turn over to showers late Monday night through
Tuesday as the remnants of the trough pass over the region. There
will be some brief ridging over the region Wednesday as another
trough deeps in the eastern Pacific. This trough will begin to
spread some warm advection type precipitation into the forecast area
late Wednesday and Thursday. The highest POPs and QPF will be
focused over the western portion of the forecast area near the
Cascades as the trough stalls off the coast. Deterministic models
very a little by Friday with the GFS being more aggressive in
bringing the trough inland while the ECMWF is slower. However, GFS
ensemble maintains the trough axis offshore keeping the forecast
area under a southwest flow and chance of precipitation.

&&

.AVIATION...12Z TAFS...Expecting mainly VFR conditions today
with some local MVFR to IFR conditions through the morning due to
low clouds and fog. Currently only DLS is being impacted but expect
improvement through the morning. Expect some precipitation to begin
this evening with lowering cigs and possible fog overnight resulting
in deteriorating conditions especially for DLS and YKM. Southerly
winds will increase ahead of this system at BDN and RDM today and
continue overnight 7-15 kts and gusts in the 20s. Downslope SE winds
will be possible in vicinity PDT and ALW overnight. All other sites
expected to remain light winds.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  49  38  48  38 /   0  30  40  10
ALW  48  37  48  40 /   0  20  30  10
PSC  43  33  44  34 /   0  30  40  20
YKM  38  30  37  28 /  10  60  50  30
HRI  44  35  46  35 /   0  40  40  10
ELN  34  28  34  28 /  10  50  50  30
RDM  45  35  46  33 /  10  30  20  20
LGD  42  35  40  34 /   0  20  30  20
GCD  43  35  42  33 /   0  30  50  20
DLS  42  36  43  35 /  20  60  60  30

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 7 PM this evening to 7 PM PST Saturday for
     ORZ049.

     High Wind Warning from 7 PM this evening to 7 PM PST Saturday
     for ORZ507.

WA...None.
&&

SHORT TERM...75
LONG TERM....91
AVIATION...91