500
FXUS66 KPDT 280938
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
238 AM PDT Mon Sep 28 2026

.KEY MESSAGES...

- Light to moderate mountain showers across the WA Cascades and
  Northern Blues with breezy low elevation winds Tuesday

- Near to above normal temperatures throughout the week

- High uncertainty in return of light mountain showers Thursday
  or Friday, with better agreement of dry conditions and above
  normal temperatures over the weekend

&&

.DISCUSSION...Little to talk about on satellite tonight as much
of the PacNW is under clear skies. At the surface, weak
diurnally winds have developed, while areas of central OR and
the Kittitas valley have seen temperatures drop into the 30s.
If winds become calm, there is a potential for radiative cooling
processes to drop temperatures to at or just below freezing
tonight (confidence 30-60%).

Today through Wednesday: Dry and quiet conditions will prevail
across the forecast area for much of today as zonal flow will
develop over the PacNW while an upper trough drops through the
Great Basin into the Desert Southwest. While winds will remain
light across much of the area, winds will increase through the
eastern Columbia Gorge ahead of an approaching cold front.

Monday night into Tuesday, flow aloft will remain zonal, however
an upper shortwave trough passing through BC will clip the WA
Cascades and northern Blue mountains. This will result in
light to moderate rain showers developing across these areas,
with a 35-45% chance of 0.1 inches in the Northern Blues and a
55-95% chance of 0.25 inches along portions of the WA Cascades
and east slopes (highest chances in central WA Cascades, lowest
south central WA Cascades). In the Columbia Basin and Gorge, a
cold front passage will result in breezy west to southwest
winds (15-25mph with gusts 25-40 mph) developing throughout the
day, with light to locally breezy winds elsewhere.

Flat upper level ridging in the eastern Pacific will build into
the western CONUS by Wednesday morning, resulting in a return to
dry conditions and light winds.

Thursday through Sunday: High uncertainty amongst deterministic
and ensemble guidance in the evolution of the synoptic pattern
Thursday through Friday, however there is good consensus amongst
the most recent ensemble members for low impacts during this
period. Overall, disagreement surrounds the eventual passage of
a shortwave trough that will bring light mountain showers. Ensemble
members are in disagreement if the trough comes through
sometime Thursday or sometime Friday, so confidence in
precipitation timing/extent is very low (15-20%).

After Friday, agreement grows in upper level ridging building
over the PacNW through the weekend, resulting in dry and quiet
conditions with above normal temperatures. (confidence 45-60%).
Lawhorn/82

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...Light and variable
winds under 6 knots are the most likely winds overnight before
mixing develops on Monday and more westerly momentum develops
through the Columbia River Gorge. DLS can see west winds gusting
to near 26 knots by late afternoon. Otherwise, expectations for
VFR conditions is of at least an 80% confidence level though
the TAF period at all terminals.

&&

.Preliminary Point Temps/PoPs...
PDT  70  44  75  51 /   0   0   0   0
ALW  71  51  75  55 /   0   0   0  10
PSC  75  45  77  49 /   0   0   0   0
YKM  73  46  73  48 /   0   0   0   0
HRI  74  48  76  51 /   0   0   0   0
ELN  68  43  64  44 /   0   0  20  20
RDM  71  36  75  40 /   0   0   0   0
LGD  71  39  75  47 /   0   0   0  10
GCD  72  40  76  45 /   0   0   0   0
DLS  76  48  73  53 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...None.
OR...None.

&&

$$

DISCUSSION...82
AVIATION...71