318
FXUS66 KPDT 031131
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
331 AM PST Wed Dec 3 2025

.DISCUSSION...Webcams show low visibilities across roads and
interstates across the Yakima Valley and the Foothills of the Blues.
Likely remain for the rest of the night as winds stay fairly light
with limited cloud cover over the effected areas currently. Fog and
freezing fog remain the primary story for tonight, as temperatures
continue to fall below freezing with the efficient radiation
cooling.

Mostly dry conditions will continue through Wednesday and through
Thursday night with dry northwesterly flow aloft continuing from the
offshore high pressure system (>90% confidence). Next weather system
will begin sometime in the later part of Thursday morning as a
shortwave with increased cyclonic vorticity aloft develops low
valley rain with light mountain snow (50-80% confidence).
Impacts start to increase Friday and towards the rest of the weekend
with a positively tilted trough from the providence`s of Manitoba
and Saskatchewan digs further south enough to trigger multiple short
waves across the Washington/Oregon area. Most of the main impacts
will be felt from the heavy mountain snow and potential wind events
at advisory level (20-60 percent chance across most of the region)
with strongest winds looking to occur late Friday afternoon through
mid Saturday morning. A warming trend will begin Thursday, giving
us a break from the below freezing temperatures we`ve observed the
past few days, with highs trending up into the low and mid 50s
through the weekend. Clusters are in agreement with a generally
narrative that we will continue to see valley rain and light
mountain snow/wintry mix go through mid next week, although to the
extent how strong/weak the system will be remains a bit uncertain
with Day 7 and being in the autumn generally bring great
uncertainty. NBM clusters are close to 50/50 to deliver a strong
or weak ridge system, but every member does advertise some form of
rain or wintry mix situation.


&&

.AVIATION...06Z TAFs...Most sites (KDLS/KPDT/KYKM/KALW/KPSC) will
have low clouds arriving through the day Wednesday, though patchy
fog lingers over KALW/KPSC overnight with KYKM joining in around
12Z (MVFR conditions or below). The fog will also drop VSBYs to
1/2SM or lower, bringing KALW/KYKM/KPSC to LIFR conditions. While
the fog may dissipate late Wednesday morning (18Z/19Z) as VSBYs
improve, low cloud decks will continue for these sites
(KDLS/KYKM/KALW/KPSC) thus keeping them between MVFR and IFR. KPDT
may see patchy fog/mist overnight (30-40% confidence), but mid to
high clouds will start returning early Wednesday morning.
KRDM/KBDN will be in VFR through this TAF period. Winds will be
less than 10kts. Feaster/97

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  41  29  42  36 /   0  10  70  70
ALW  39  31  41  36 /  10  10  80  70
PSC  38  28  40  31 /   0  10  60  40
YKM  38  28  42  29 /  10  10  40  30
HRI  39  29  41  34 /   0  10  70  50
ELN  38  27  41  30 /  10  20  40  40
RDM  45  25  47  34 /   0  10  40  30
LGD  41  26  41  36 /   0  10  80  80
GCD  42  26  43  37 /   0   0  70  80
DLS  44  37  47  42 /  10  20  70  60

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Freezing Fog Advisory until 10 AM PST this morning for ORZ507.

WA...Freezing Fog Advisory until 10 AM PST this morning for WAZ027-
     029.

&&

$$

SHORT TERM...95
LONG TERM....95
AVIATION...97