152
FXUS66 KPDT 101127
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
327 AM PST Mon Nov 10 2025

.DISCUSSION...

Key Messages:

1. Breezy winds persist this morning.

2. Mountain/foothills showers today, widespread Wednesday onward.

3. Pass level snow Thursday through the weekend.


Current radar and infrared satellite imagery showing light returns
approaching the Washington Cascade crest under partly to mostly
cloudy skies. Area webcams are indicating some patchy fog in areas
along highway 12 west of Walla Walla, potentially developing
around the Tri-Cities and Pendleton areas - so use caution if
traveling in these areas through the morning hours. This is in
response to a weak upper level shortwave that is approaching the
coast, and will move through the area later today. The upper level
ridge that brought dry and mostly sunny conditions to the area
over the weekend has suppressed and shifted east, which is
keeping a developed pressure gradient along the Blue Mountains
through the morning. This has resulted in breezy winds across the
Grande Ronde Valley with gusts reaching 40-50 mph over the
previous 24 hours. These winds will continue through the morning
until slowly subsiding through the afternoon and evening as the
pressure gradient slackens with the weakening ridge of high
pressure. The NAM and SREF advertise a pressure gradient of
6.2-6.5 mb between Meacham (KMEH) and Baker City (KBKE) through
mid-morning, dropping to less than 3 mb after 11 AM. Until then,
sustained south winds of 20-30 mph with gusts of up to 45 mph will
be possible - specifically near Ladd and Pyles Canyons.
Confidence in these wind values is high (75-85%) as the HREF
suggests a 50-60% chance of gusts reaching 40 mph or greater
before 3 AM, and a 40-50% chance between 3 AM and 8 AM. After 8
AM, chances drop considerably to below 20%.

The weak upper level shortwave and associated cold front poised to
pass through the area today from the northwest will attribute to
mountain showers through the day. Showers will begin across the
Washington Cascades this morning, Oregon Cascades around noon, and
the northern Blue Mountains and foothills late afternoon and
evening. Snow levels will be quite high (7000-8000 feet), so
any snowfall will be light and occur at high elevations. Rain
accumulations of 0.15-0.25" over the Cascade crest and Northern
Blue Mountains, and 0.01-0.10" across the northern Blue Mountain
foothills are expected today, with drying conditions tonight into
Tuesday morning as a transient upper level ridge passes through
early Wednesday.

A strong, more substantial system will be approaching the coast
Wednesday before passing through the Pacific Northwest Thursday
and Friday followed by an embedded shortwave on Saturday. These
synoptic features will keep widespread rain chances and mountain
snow in the forecast through the remainder of the week, peaking
Thursday and Saturday. However, ensemble members are still in
disagreement with the overall strength and timing with 44% of
members hinting at an earlier arrival and 56% suggesting a
stronger, deeper upper level trough. Differences in how broad the
system is expected to be are also present in deterministic and
ensemble guidance, which would relate to overall precipitation
amounts (residence time). This is all to say that confidence is
lacking (30-50%) in regards to the rain and snow amount forecast,
but pass snow amounts have been slowly trending upward over the
last 48 hours. Snow levels will be hovering between 6500-7500 feet
Wednesday before dropping to 4000-5000 feet Thursday and
3500-4500 feet on Friday. This will allow for substantial pass
level snowfall Thursday and Friday, with Santiam and White Passes
being impacted with daily snow accumulations of 4 and 2 inches
respectively. These values over Santiam Pass reach warning
criteria (>8 inches), which is reflected by a 60-65% chance of
occurrence via the NBM. White Pass is forecast to reach 5 inches
during this timeframe, which is just shy of advisory criteria (6
inches).

This more substantial system will bring widespread rain chances
through the remainder of the week. Rain amounts of 0.10-0.30"
along the Cascade Crest and less than 0.03" across Central Oregon
and the east slopes of the Cascades on Wednesday. Thursday`s
expected rain amounts are 0.20-0.50" over the Cascades,
0.10-0.30" along the northern Blue Mountains and Wallowa county,
and less than 0.10" over the foothills, Central Oregon, and the
Lower Columbia Basin. Friday`s rain amounts look to be more
confined to the east slopes of the Cascades, eastern mountains,
and the John Day Basin with up to 0.10" over lower elevations and
up to 0.25" in higher terrain. Widespread rain coverage looks to
return on Saturday and Sunday, with current expected rain amounts
similar to Thursday`s values. One thing to note is that the
confidence in guidance decreases substantially over the weekend,
so these amounts should be lightly considered. 75




&&

.AVIATION...12Z TAFs...Predominantly VFR conditions are forecast for
all sites over the next 24 hours. CIGs will lower from west to east
this afternoon and evening, with a 20-30 percent chance of light
rain at DLS/PDT/ALW/PSC; chances of rain are less than 20 percent
elsewhere. Low-end VFR to high-end MVFR CIGs (2500-5000 ft) are
likely (70 percent confidence) late afternoon into the early
overnight hours at PDT/ALW, with low confidence (20 percent or less)
in sub-VFR CIGs at other sites. VSBYs of 6-10 miles are likely (70
percent confidence) at PSC/PDT this morning. Cannot rule out sub-VFR
VSBYs in BR or FG, but confidence in any sustained periods of
reduced VSBYs is too low to include mention in the 12Z TAFs. Winds
will be mostly 10 kts or less, with a few hours of gusts forecast at
DLS/BDN/ALW late morning and afternoon.


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  61  40  57  39 /  10  20   0  10
ALW  60  43  56  42 /  20  30   0  20
PSC  58  34  55  38 /  10  10   0  10
YKM  57  33  55  37 /  10   0   0  10
HRI  60  39  55  40 /  10  10   0  10
ELN  55  32  52  34 /  20   0   0  10
RDM  64  34  62  39 /   0   0   0   0
LGD  62  42  62  45 /  10  20   0  10
GCD  66  38  65  43 /   0   0   0   0
DLS  61  42  57  44 /  30  10   0  10

&&

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

$$

SHORT TERM...75
LONG TERM....75
AVIATION...86