246
FXUS66 KPDT 021757
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
957 AM PST Mon Nov 2 2026

.KEY MESSAGES...
- Patchy to areas of dense freezing fog this morning, mainly
  for the Blue Mountains region and fog-prone valleys within the
  Columbia Basin.

- Near-normal temperatures and mostly dry conditions until a
  weak weather system arrives late Wednesday.

&&

.DISCUSSION...
GOES-18 water vapor imagery shows an amplified upper-level
ridge extending from California northeast through the Canadian
Rockies. Upstream in the Pacific, a low-pressure system is
developing in the vicinity of 39N, 142W. Nighttime microphysics
imagery reveals mostly clear skies across the forecast area,
albeit with low stratus and/or fog in portions of the eastern
Columbia River Gorge, lower Columbia Basin, Blue Mountains, and
cold mountain basins. At the surface, most valley/basin
locations are nearly saturated at around 90-100% RH, and
additional fog formation remains a concern for early morning.
Have held off on any headlines due to the patchy nature, but
will continue to monitor the situation.

The aforementioned area of low pressure is expected (90%
confidence) to develop into a closed low by Tuesday, eventually
moving inland over southern Oregon or northern California by
late Tuesday. Ensemble guidance suggests the low will be too far
south to produce significant precipitation for our forecast
area, and mostly dry conditions (PoPs of 20% or less) are
forecast to continue until late Wednesday into Thursday when
ensemble guidance highlights the arrival of a shortwave trough.
Clusters of ensemble solutions continue to indicate significant
spread in how much precipitation will accompany the shortwave;
roughly one-third of members place noteworthy precipitation
across the forecast area, while the remainder keep
precipitation confined to the Cascade crest.

By Friday, ensemble clusters are showing medium potential (~65%)
of wet weather for the Washington Cascades, with significantly
lower chances (~30%) for wet weather east of the Cascades.
Ensemble guidance is trending towards mostly dry solutions
(75-85%) by Saturday with an upper-level ridge overhead and
precipitation displaced to the northwest of our forecast area.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...

KDLS is buried in stratus with 700 ft ceilings this morning and
the LAMP guidance in addition to REFS sounding profiles
suggests these ceilings breaking out by 19 or 20z. Elsewhere,
where localized brief fog occurred, the visibilities have
improved to VFR. Light winds at all terminals through the TAF.

&&

.Preliminary Point Temps/PoPs...
PDT  58  36  50  30 /   0   0  10   0
ALW  57  39  50  34 /   0   0   0   0
PSC  58  38  54  31 /   0   0  10   0
YKM  55  39  57  31 /   0   0  10   0
HRI  58  38  52  30 /   0   0  10   0
ELN  53  34  52  28 /   0   0  10   0
RDM  59  31  51  23 /   0   0   0   0
LGD  53  37  56  31 /   0   0   0   0
GCD  57  36  58  31 /   0   0   0   0
DLS  59  41  58  35 /   0  10  10   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...None.
OR...Dense Fog Advisory until noon PST today for ORZ050.

&&

$$

DISCUSSION...86
AVIATION...71