195
FXUS66 KPDT 240412
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
912 PM PDT Fri Oct 23 2026

.KEY MESSAGES...
- Dry conditions will persist into the weekend as a ridge of
  high pressure moves overhead.

- Near- to sub-freezing low temperatures tonight into Saturday
  morning. Freeze Warnings in effect.

- High confidence (70-90%) in cooler conditions and periods of
  showery weather early next week, followed by medium confidence
  (40-60%) in periods of active weather middle to late week.

&&

.DISCUSSION...
Water vapor imagery shows broad troughing over the western
CONUS, moving out of our forecast area. Meanwhile, precipitation
has tapered off across the Blue Mountains as a very dry
northerly to northwesterly flow aloft replaces the previous air
mass and a low-amplitude upper-level ridge moves overhead.
Morning soundings (12Z or 18Z) at SLE, OTX, MFR, and UIL all
show low PWATs of 0.25-0.35" and 12Z HREF model guidance
suggests values ranging from 0.15" to 0.45" across the forecast
area today into tonight. Lingering breezy conditions will taper
off this evening into tonight. Moreover, the combination of
clear to mostly clear skies and the dry air mass has set the
stage for near- to sub-freezing temperatures tonight into
Saturday morning. While most public forecast zones have observed
a season-ending freeze, a widespread freeze has not yet
occurred in the lowest elevations of our forecast area.
Confidence is medium-high (50-95%) that a season-ending freeze
will be observed in the lower Columbia Basin, eastern Columbia
River Gorge, Yakima Valley, and the foothills of the northern
Blue Mountains. Lowest confidence in a widespread freeze is for
the eastern Columbia River Gorge; highest confidence in a
freeze is for cold-prone locations along the Blue Mountain
foothills and lower Columbia Basin. That said, opted to upgrade
all Freeze Watches to Freeze Warnings.

Uncertainty in the 500-hPa height field burgeons Sunday through
the remainder of the forecast period due to continued ensemble
spread in solutions regarding the evolution of a closed low
that is currently developing in the Gulf of Alaska. While
ensemble solutions have begun to cluster around a closed low
entering, then tracking inland, across the Pacific Northwest
region later Sunday through Tuesday of next week, significant
uncertainty remains with regard to the track of the low, the
depth of the low, and how quickly it will move inland. Based on
12Z ensemble guidance, the best chances of precipitation will
be Monday and Tuesday. Even then, chances of a wetting rain
(0.10" or greater) are low (40% or less) for the lower
elevations, Washington Cascades, and Ochoco-John Day Highlands.
Higher chances (40-70%) of a wetting rain are forecast for the
Oregon Cascades and northeast Blue Mountains.

Ensemble solutions are roughly split (50/50) Wednesday through
the remainder of the week on whether another trough/closed low
or ridge will be present over the Pacific Northwest. Continued
cool, showery weather would accompany the closed low or
troughing scenario, while dry conditions would result from the
ridge.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
High pressure will create light and variable winds overnight
(under 5 knots). More consistency in wind direction will
develop on Saturday (under 10 knots). Clear sky or cirrus and
VFR conditions at all terminals.


&&

.Preliminary Point Temps/PoPs...
PDT  26  58  30  58 /   0   0   0   0
ALW  32  59  37  59 /   0   0   0   0
PSC  28  59  28  58 /   0   0   0   0
YKM  30  58  32  58 /   0   0   0   0
HRI  29  57  30  57 /   0   0   0   0
ELN  24  55  24  54 /   0   0   0  10
RDM  18  59  26  63 /   0   0   0   0
LGD  25  59  33  61 /   0   0   0   0
GCD  25  60  29  64 /   0   0   0   0
DLS  34  62  35  60 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...Freeze Warning until 10 AM PDT Saturday for WAZ024-027>029.
OR...Freeze Warning until 10 AM PDT Saturday for ORZ041-044-507.

&&

$$

DISCUSSION...86
AVIATION...71