172
FXUS66 KPDT 221115
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
315 AM PST Sat Nov 22 2025


.UPDATED AVIATION.

.AVIATION...12Z TAFs...Light winds with mostly VFR conditions for
all sights with the notable exception of PSC. PSC currently
experiencing LIFR conditions that will prevail for most of the
morning hours. Expecting the fog to lift once we get closer to the
afternoon hours with daytime heating mixing out the fog. Guidance
shows fog re-entering PSC sometime late Saturday afternoon into
the early evening. Went ahead and put another group for potential
quarter mile visibility starting again at 05Z. Other sites will
see some visibility shuffle between 6 to 10 SM through the night
but not anticipating any long term fog for the period. All sites
remain at a low chance (5-15% chance) for some brief sub-VFR
conditions from visibility or low ceilings.


&&

.PREV DISCUSSION... /issued 300 AM PST Sat Nov 22 2025/

DISCUSSION...

A 1028 mb surface high pressure was centered over eastern Oregon
This morning. Fog was present on a number of metar and road cams
across the Tri-Cities area with an HREF signal for dense fog/low
visibility snowing up with a 25-50% chance for less than one
quarter mile through at least 17z, focused throughout the river
basin. A dense fog advisory will remain in effect for Franklin and
Benton Counties in WA through 10 am. Light winds Today will give
way to increasingly breezy southwesterly surface winds for Sunday
as the High pressure moves away, pressure falls and a cold front
approaches the area from be PAC NW for late Sunday and Sunday
night. From the standpoint of the EFI, nothing stands out as
particularly strong with these episodes this week, as the NAEFS
Standardized Anomalies are only around 1 to 1.5 for any given
weather element. Having said that, still, pass level snow possible
Sunday and Wednesday. For Snoqualmie, around 4 inches based on
the NBM for the entire duration (below advisory criteria) for each
of the two separate precipitation episodes. Probabilistic Winter
Storm Severity Index brings out little to no chance for moderate
impacts due to snow load on Sunday, however does increase this to
about a 20-30% chance at the Pass by Wednesday Afternoon
(differentiated by minor impacts by closures and disruptions to
infrastructure possible). A similar snow impact might be found at
White Pass, as these will be wet snows with low snow to liquid
ratios (around 8:1). Breeziest conditions for the week look to be
in the post frontal environment Sunday Night into Monday as
westerly surface gusts are being produced by the NBM mean around
25 to 35 knots which is pushing 30 to 40 mph across the Eastern
Columbia River Gorge, Simcoe Highlands and northern Blues
Mountains, as well as much of the Oregon Columbia Basin.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  51  34  52  32 /   0   0  30  60
ALW  50  39  53  34 /   0   0  50  80
PSC  47  33  51  32 /   0  10  30  30
YKM  49  35  50  26 /   0  10  30  20
HRI  47  34  52  34 /   0   0  30  40
ELN  47  34  47  29 /   0  20  60  30
RDM  57  28  54  23 /   0   0  20  20
LGD  53  35  52  29 /   0   0  20  80
GCD  55  31  56  28 /   0   0  10  60
DLS  52  39  52  37 /   0  10  70  50

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Dense Fog Advisory until 10 AM PST this morning for WAZ028.

&&

$$

SHORT TERM...71
LONG TERM....71
AVIATION...95