484
FXUS66 KPDT 181128
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
328 AM PST Tue Nov 18 2025

Updated Aviation Discussion

.AVIATION...12z TAFs...Low, MVFR cigs will linger around several
sites (namely PDT, PSC, RDM, and BDN) early this morning, before
some clearing is expected heading into the afternoon. A deck of
bkn-ovc cigs around 15 kft will then move in, before much of the
area sees clearing once again late Tuesday evening. Low cigs and
even fog may return toward the very tail end of the period, given
the light winds and relatively clear skies expected in the evening
prior. Otherwise, for the afternoon hours, VFR conditions are
anticipated. 74

&&

.PREV DISCUSSION... /issued 306 AM PST Tue Nov 18 2025/

DISCUSSION...Today through Wednesday: A shortwave trough to the
north continues to drag a cold front boundary across the far
eastern WA tonight, with light showers now diminishing in the
lower Columbia Basin. Breezy winds have developed with the frontal
passage, with breezy winds along the Blue mountain foothills and
portions of the Columbia Basin expected to continue through
sunrise this morning. Otherwise, plenty of clearing has occurred
behind the frontal passage, with the back end of the associated
stratus layer entering eastern portions of the Basin.

The next in a series of shortwaves will pass over the PacNW today,
however a lack of moisture with this system will only result in
light precip along the WA Cascade crest and interior northern
Blues through this afternoon, with precip consisting of snow or a
rain/snow mix near pass levels. A colder and drier airmass will
filter into areas east of the Cascade crest tonight, and coupled
with clearing skies, lower elevation locations and mountain
valleys will be looking at morning low temperatures below freezing
Wednesday. There is moderate-high confidence (65-85%) that areas
of the eastern Columbia River Gorge will see their first freeze of
the fall/winter, which has resulted in a season ending freeze
warning for Wednesday morning. In tandem with the clearing skies
and lower temperatures, more moist conditions near the surface may
also result in areas of patchy dense fog/freezing fog developing across
the lower elevation and mountain valleys (confidence 40-65%)
Wednesday morning, though confidence is low (15-25%) in the
details for where and when fog may develop. Wednesday, a
transient upper ridge will slide over the PacNW, resulting in dry,
cool conditions with light winds.

Thursday through Saturday: A semi-active weather pattern, though
with light precipitation, will continue through the latter half of
the work week into the weekend. Ensemble GFS and ECMWF guidance
are in agreement of an upper trough approaching the PacNW
Wednesday night, then transitioning into a closed low that will
dive south along the coast and into CA Thursday. The closed low
will clip the western and southern portions of the forecast area,
resulting in light rain and mountain snow across the Cascade
crest as well as across portions of central OR and the Blues
(confidence 50-70%). Dry conditions will briefly develop Thursday
night as the low moves further south of the region, but light
rain with light snow mainly above 5kft to 6kft will redevelop
along the Cascade crest and northern Blues Friday through the
weekend as zonal flow develops aloft (confidence 50-75%).

Sunday through Monday:Ensemble cluster guidance shows good
agreement that the zonal flow aloft will persist through Sunday
afternoon, with a southerly component developing as a trough
dives down the BC coast. Sunday night through Monday, ensemble
guidance comes into disagreement in timing and strength of the
trough passage. One solution (GFS member majority) has the trough
axis overhead by Monday afternoon, while another solution (ECMWF
member majority) has the trough axis still offshore. The latter
solution would delay more widespread precip while the former
would result in widespread precip chances by early Monday morning.
What these solutions do agree upon is that snow chances would
be limited to the mountain zones. That said, there is yet another
solution (made up of ECMWF and GFS members) that would arrive with
a much colder airmass and widespread light snow or rain/snow mix
to the lower elevations Monday. While confidence is moderate
(40-65%) in widespread precipitation chances across the forecast
area Sunday night into Monday, confidence is low (10-20%)
precipitation type and amounts. Lawhorn/82

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  50  30  48  31 /   0   0   0  10
ALW  49  34  48  34 /  10  10   0  10
PSC  52  29  49  31 /   0   0   0  10
YKM  50  29  49  31 /   0   0   0  10
HRI  51  30  48  31 /   0   0   0  10
ELN  47  27  46  29 /  10  10   0  20
RDM  48  21  51  26 /   0   0   0  20
LGD  50  29  51  33 /  10  10   0  10
GCD  50  31  54  34 /   0  10   0  20
DLS  52  34  50  37 /   0   0   0  30

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Freeze Warning from 11 PM this evening to 10 AM PST Wednesday
     for ORZ041.

WA...Freeze Warning from 11 PM this evening to 10 AM PST Wednesday
     for WAZ024.

&&

$$

DISCUSSION....82
AVIATION...74