346
FXUS66 KPDT 270645
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1045 PM PST Wed Nov 26 2025

.UPDATE...

Current infrared satellite imagery and local webcams confirm the
presence of dense fog across Central Oregon, Blue Mountain
foothills of Oregon, and the John Day Basin. These conditions are
impacting the Interstate 84 and Highways 97, 11, and 19 corridors
and are not expected to improve until mid-morning. Visibilities of
lower than one quarter mile are currently being observed, so use
extra caution if traveling on the earlier mentioned
thoroughfares. A Dense Fog Advisory has been issued for these
areas until 10 AM Thursday. 75

&&

.PREV DISCUSSION... /issued 958 PM PST Wed Nov 26 2025/

Updated Aviation Discussion.

AVIATION...06Z TAFS...Variable conditions across sites, with VFR at
KRDM/KBDN, MVFR at KDLS/KYKM/KPSC, and LIFR at KPDT/KALW due to
reduced ceilings of .5kft and visibilities of 1/4SM respectively.
These LIFR conditions are expected to persist through the
majority of the period as a system passes through the region. KYKM
is also forecast to reach IFR conditions in the early morning
hours due to ceilings of .7-.9kft, which will extend through
Thursday evening. Winds will stay light and below 10 kts, with the
exception of KRDM/KBDN which will experience sustained winds of
10-12 kts and gusts of 20-22 kts late Thursday morning through
the afternoon associated with the frontal passage. Light rain will
also impact all sites by late morning and again toward the end of
the period. The only terminals to stay dry will be KRDM/KBDN. 75

PREV DISCUSSION... /issued 235 PM PST Wed Nov 26 2025/

DISCUSSION...Today through Friday: Satellite and radar imagery
show a warm front boundary across the northern tier of OR this
afternoon, with light rain being observed from the Gorge south to
Madras, as well as across the OR Cascade crest.

The warm front boundary will gradually continue to lift north and
east through tonight, with light rain and high mountain snow
developing behind the boundary. In addition to rain/snow, smaller
valleys along the WA Cascade east slopes may see very light
freezing rain develop this evening and tonight as the warmer
airmass initially extends over these areas.

Thanksgiving day, a cold front then an associated vertically
stacked low pressure system will swing into the PacNW, bringing
with it a round of light rain and mostly a rain/snow mix above
5kft in the mountains (mainly snow above 6-6.5kft). The low will
exit the region by Friday afternoon, with drying conditions
setting up as remnants of a ridge slide southeast across the
region late Friday.

Snow accumulations through Friday will be very light at pass
level, with the chances of 1 inch of snowfall less than 10% at
Snoqualmie and Santiam passes, ~15% over the northern Blues, and
only a 30% at White pass.

Saturday through Sunday: Ensemble cluster solutions are in good
agreement that a shortwave trough will dive down the backside of
ridging in the northeast Pacific on Saturday, but that`s about
where the agreement ends. Ensemble cluster members (ECMWF, GFS,
Canadian ensemble suites) are in disagreement in whether the
trough arrives to the region Saturday morning or Saturday
evening, and whether there will be widespread light snow, or the
light snow will be limited to central OR and the Blue Mountain
foothills. As to how light the snow may be in the lower
elevations, the NBM is only showing a 10-25% chance of 0.1 inches
of snow across the Blue Mountain foothills, central OR, Kittitas
valley, and ridges around Yakima valley. Meanwhile, chances in the
mountain zones only reach 50% through Sunday morning. Overall,
confidence is moderate (45-65%) that precipitation will remain
light as this system impacts the forecast area, however,
confidence precip type and timing is low (15-30%) given the timing
differences amongst ensemble solutions, and deterministic
guidance for that matter.

By Sunday afternoon, there is good consensus that dry, cold
conditions will return to the forecast area as the shortwave
trough exits to the southeast and ridging offshore places the
region under a northerly flow aloft. Dry conditions under the
northerly flow will continue into Monday, with Sunday night low
temperatures in the mid 20s in the lower elevations (confidence
35-60%).

Monday through Tuesday: Good agreement amongst ensemble solutions
continues into early next week, as ensemble model guidance depicts
the upper ridge offshore flattening as a trough swings up and over
into the PacNW (confidence 40-55%). This system will bring another
round of light snow to the mountains(confidence 30-50%), though
confidence is low (15-20%) in whether the lower elevations will
see any of precipitation with this system. Lawhorn/82

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  35  46  36  44 /  60  60  90  90
ALW  37  45  38  44 /  60  70  90  90
PSC  37  45  36  49 /  60  80  90  60
YKM  37  43  36  49 /  70  90  90  40
HRI  37  45  37  47 /  60  70  90  80
ELN  33  40  32  45 /  60  90  90  30
RDM  29  55  31  50 /   0  20  30  20
LGD  34  48  36  44 /  60  40  80  90
GCD  34  53  34  46 /  20  20  30  60
DLS  42  48  41  51 /  70  90  90  70

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Dense Fog Advisory until 10 AM PST Thursday for ORZ505-507-508-
     510-511.

WA...None.
&&

$$

UPDATE...75
DISCUSSION....82
AVIATION...75