826
FXUS66 KPDT 011745
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
945 AM PST Sun Nov 1 2026

.KEY MESSAGES...
- Areas of dense fog and freezing fog today.

- Near- to below-normal temperatures into next week.

- Low chance (30% or less, except for freeze-prone areas) of a
  season-ending freeze for the eastern Columbia River Gorge
  Monday.

&&

.DISCUSSION...
Water vapor imagery shows a splitting trough over the forecast
area, with the main circulation centers tracking over northern
California and the Canadian Rockies. Nighttime microphysics
imagery reveals middle and high cloud cover across far eastern
Oregon and Washington, while much of central to eastern Oregon
and southeast Washington are under a blanket of low stratus.
Elsewhere, mostly clear skies are noted over south-central
Washington. Radar reveals isolated showers over the Columbia
Plateau, mainly near and north of Walla Walla. At the surface,
most valley locations are nearly saturated at around 90-100%
RH, and additional fog formation remains a concern for early
morning. Have issued a Dense Fog Advisory for the northern and
southern Blue Mountains where low stratus is intersecting the
terrain and creating near-zero visibility in places; this low
visibility is affecting routes over the Blue Mountains including
but not limited to Interstate 84, Highway 395, and Highway 204.
Elsewhere, patchy to areas of dense fog and dense freezing fog
are present in central Oregon; have issued a Special Weather
Statement for this fog, though if it becomes more widespread, an
advisory may be needed.

Ensemble guidance indicates the trough will exit to the east
this evening, and an amplified upper-level ridge will build in
from the Pacific through Monday. Given clearing skies and dry
conditions, this presents the best chance, albeit low at 30% or
less, of a season-ending freeze for the eastern Columbia River
Gorge in the next week. Freeze-prone portions of the Gorge do
have somewhat higher chances of freezing (locally in excess of
50%), but at this time confidence remains too low to issue any
watches.

Uncertainty in the 500-hPa pattern then grows Tuesday through
the remainder of the week. Ensemble clusters show a range of
solutions regarding a compact closed low Tuesday into Wednesday.
The majority of solutions (~80%) take the low too far south
across southern Oregon or northern California to produce
significant precipitation for our forecast area, and mostly dry
conditions (PoPs of 20% or less) are forecast to continue until
late Wednesday when ensemble guidance hints at the return of
some more active weather in the form of a shortwave trough. By
Friday and Saturday, ensemble clusters are showing medium
potential (roughly 50% chance) for a return to a wet pattern.
NBM probabilities indicate a low-medium (20-60%) chance for at
least 0.50" of precipitation across the Cascades and northern
Blue Mountains during the Friday through Saturday period;
highest chances are for the Washington Cascades. That said, the
alternate scenario is for an upper-level ridge to be overhead
with precipitation displaced to the northwest of our forecast
area.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...


Scattered clouds under 1000 ft over DLS for the next few with
about a 20% chance for the deck returning to broken or overcast
though mid afternoon. Satellite shows some erosion of the cloud
deck covering RDM and BDN with 800 ft overcast ceilings, however
it is slow, and by may take until about 21-22z to scatter out
based on the the HRRR model trends. Visibility improving at ALW
to VFR by the end of the afternoon. Light and variable, VFR
elsewhere. &&

.Preliminary Point Temps/PoPs...
PDT  30  56  34  52 /   0   0   0   0
ALW  34  55  38  53 /   0   0   0   0
PSC  30  54  34  55 /   0   0   0   0
YKM  31  54  37  57 /   0   0   0   0
HRI  30  55  34  54 /   0   0   0   0
ELN  25  50  31  52 /   0   0  10   0
RDM  22  56  27  52 /   0   0   0   0
LGD  29  54  36  57 /   0   0   0   0
GCD  30  57  36  58 /   0   0   0   0
DLS  33  56  40  57 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...None.
OR...Dense Fog Advisory until noon PST today for ORZ502-503.

&&

$$

DISCUSSION...86
AVIATION...71