047
FXUS66 KPDT 171125
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
325 AM PST Mon Nov 17 2025

Updated Aviation Discussion

.AVIATION...12z TAFs...Low cigs and fog will once again impact TAF
sites early this morning. PSC and DLS have already reported dense
fog, with YKM also reporting IFR cigs this morning. Made mention
of low cigs potentially impacting ALW and PDT, but confidence is
low to moderate (30-40%), but high enough to at least warrant a
mention. Confidence is higher (50-60%) in BDN/RDM staying VFR
through the period. Cigs are expected to lift by late morning,
with winds picking up slightly up to 10 kts at most sites, which
should help stave off the fog threat for tomorrow night. Still,
MVFR cigs may linger into the afternoon, especially for PSC and
DLS. 74

&&

.PREV DISCUSSION... /issued 307 AM PST Mon Nov 17 2025/

DISCUSSION...Today through Wednesday: A band of light showers
associated with a passing shortwave continues to transit eastern
portions of the Columbia Basin tonight, while patches of dense fog
with visibilities down to a quarter mile and low stratus have
developed across western portions of the Columbia Basin, including
adjacent valleys and the eastern Gorge. Meanwhile, very light
showers straddling the OR Cascade crest are currently pushing
north and nearing the OR/WA border. These showers are associated
with a trough centered offshore the western CONUS.

By mid-morning, a brief lull in precip activity will develop
across the forecast area as the main low circulation in the trough
offshore dives south, leaving behind a weaker low circulation
over Vancouver Island. Some light precip will continue across the
Cascade crest, northern Blues, and Wallowa mountains through this
morning. The low will transit the PacNW late this afternoon and
tonight, providing mainly light precip to the WA Cascades and
northern Blues, though low chances (15-35%) of light rain will be
possible into portions of the Columbia Basin north of the Horse
Heaven Hills and Rattlesnake mountain, and along the northern Blue
Mountain foothills. Snow levels will fall to pass level tonight,
resulting in a transition from rain to rain/snow mix, then to snow
by middle of the night. A shortwave trough will quickly follow-
up the low as it exits to the northeast Tuesday afternoon, though
precip will be much lighter, with mainly snow or rain/snow mix
developing across the Cascade crest and Blue mountains. Tuesday
night, precip chances will come to an end across the forecast area
as a transient ridge of high pressure moves inland, with dry
conditions continuing into the overnight hours. Clearing cloud
cover and a colder airmass filtering into the region will result
in near to below freezing low temperatures across the lower
elevations of the forecast area, with moderate confidence (60-75%)
that portions of the eastern Columbia River Gorge will see their
first freeze of the fall/winter.

Thursday through Sunday:An active weather pattern, though with
light precipitation, will continue through the latter half of this
week. Ensemble 00Z guidance is in better agreement tonight of an
upper trough approaching the PacNW, then transitioning into a
closed low that will dive south along the coast and into CA. The
closed low will clip the forecast area, resulting in light rain
and mountain snow developing across the Cascade crest as well as
across portions of central OR and the Blues. Dry conditions will
briefly develop Thursday night as the low moves further south of
the region, but light rain and high elevation snow will redevelop
along the Cascade crest and far northern Blues Friday through the
weekend as zonal flow develops aloft (confidence 45-70%).

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  58  38  50  30 /  40  30  20   0
ALW  56  42  49  34 /  50  40  30  10
PSC  57  38  52  30 /  20  20  10   0
YKM  56  33  51  29 /  30  30   0   0
HRI  58  39  51  30 /  30  30  10   0
ELN  53  33  47  27 /  50  50  10   0
RDM  56  30  48  20 /  40  10   0   0
LGD  56  38  50  27 /  60  30  30  10
GCD  57  36  51  29 /  50  20  20  10
DLS  56  40  53  34 /  60  20  10   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&

$$

DISCUSSION...82
AVIATION...74