594
FXUS66 KPDT 242304
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
304 PM PST Mon Nov 24 2025

.DISCUSSION...The shortwave trough that brought widespread breezy
to locally windy conditions and light to moderate rainfall to the
forecast area overnight into this morning has exited to the east.
Aside from isolated to scattered light snow showers this afternoon
across the Washington Cascade crest, dry conditions will continue
through tonight. Breezy winds across the Columbia Plateau will
continue to diminish in magnitude this afternoon, becoming light
overnight as pressure gradients slacken and winds aloft decrease.

Tonight, temperatures are anticipated to drop below freezing
across most of the forecast area, including the lowlands, setting
the stage for wintry precipitation where temperatures fail to rise
above freezing Tuesday.

To dive into specifics for Tuesday through Thursday, ensemble
solutions generally drape a warm front and sub-tropical moisture
plume (visible on satellite offshore in the Pacific) over the
forecast area by late Tuesday morning. The location of the front
and moisture plume as presented by ensemble members ranges from
north-central Oregon to south-central Washington, with the bulk of
the precipitation associated with the system likely (70 percent
confidence) concentrated across the northern half of our forecast
area. Meanwhile, near- to sub-freezing air at the surface is
likely (70-95 percent confidence) across south-central
Washington. As time progresses, solutions range from a slow-
moving or even quasi-stationary frontal boundary persisting
across the forecast area Tuesday afternoon through Wednesday night
to a faster-moving frontal boundary that pushes into northern
Washington (out of our forecast area) by Wednesday afternoon.
Based on the latest 12Z and 18Z NWP guidance, a break in wintry
precipitation is favored by mid-Wednesday morning, with
additional periods of precipitation existing through Thursday
night.

So will wee see wintry precipitation in the lowlands? The NBM
suggests a low probability (20-60 percent) of 1 inch or greater
snowfall for the 24-hr period ending 10 AM PST Wednesday for the
Kittitas Valley, with lower probabilities of less than 10 percent
for the Grande Ronde and Yakima valleys. In the eastern half of
the Columbia Basin and farther south into central Oregon, guidance
is more confident in a warmer air mass (south of the warm frontal
boundary), resulting in very low probabilities of measurable
snowfall (less than 5 percent). Probabilities of measurable
freezing rain have increased, and are now low-medium (generally
20-60 percent) Tuesday night through Wednesday in sheltered
valleys along the east side of the Washington Cascades and Blue
Mountains.

Thermodynamic profiles in NWP guidance are supportive of snow
Tuesday morning before transitioning to a rain/snow mix and/or
light freezing rain Tuesday night into Wednesday morning. The main
areas of concern remain the Washington Cascades and their eastern
slopes as well as the Kittitas Valley, and Winter Weather
Advisories have been issued, valid 10 AM PST Tuesday through 4 AM
PST Wednesday. Confidence in advisory-level snowfall was too low
(40-60 percent) for the northern Blue Mountains to issue any
headlines with the afternoon forecast package.

Looking ahead, an Arctic air mass is possible (a solution
presented by 40 percent of ensemble members) by the weekend into
early next week. Will lowland snow accompany this cooler air mass?
Confidence is still too low to discuss details, so stay tuned for
more details in the coming days.

&&

.AVIATION...00Z TAFs...Mix of conditions through the period,
starting with VFR, then MVFR or lower developing tomorrow at
several sites. There are low chances (15-25%) of MVFR vsby
developing at site PSC around or after 12Z. Otherwise, cloud cover
increases late tonight as a low pressure system approaches the
region. As the low approaches nearer, precipitation chances will
increase across the WA sites and the DLS from west to east, with
site YKM the only site expected to see a rain/snow mix, with a 30%
chance of light snow and MVFR or lower CIGS/vsby in the late
morning and early afternoon. Otherwise, all the other WA sites
will see light rain develop with lowering CIGS down to AOA 4kft
AGL. Breezy winds 12-17kts with gusts up to 25kts will diminish at
sites DLS/PDT over the next few hours. Otherwise, light winds,
12kts or less, will prevail through the period. Lawhorn/82

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  28  45  35  47 /   0  40  70  50
ALW  33  45  37  45 /   0  40  80  60
PSC  28  42  34  44 /   0  40  70  40
YKM  28  40  30  42 /   0  60  70  50
HRI  28  42  35  44 /   0  40  70  50
ELN  26  37  28  39 /   0  70  80  50
RDM  22  50  32  55 /   0  20  30  20
LGD  24  44  33  47 /   0  30  80  60
GCD  26  48  35  52 /   0  20  50  40
DLS  34  43  38  46 /  10  60  80  70

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Winter Weather Advisory from 10 AM Tuesday to 4 AM PST Wednesday
     for WAZ026-522-523.

&&

$$

DISCUSSION...86
AVIATION...82