467
FXUS66 KPDT 042247
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
247 PM PST Wed Nov 4 2026

.KEY MESSAGES...

- Light rain this evening through Thursday morning.

- Mountain showers return Friday and Sunday morning.

- Breezy weekend winds, primarily late Saturday into Sunday.

&&

.DISCUSSION...
Current radar and visible satellite imagery shows dry conditions
as clouds begin to develop along the Cascade and Blue Mountains.
This is in response to the high pressure ahead of an incoming
system that is already bringing light showers along the coastal
range. Showers will begin to impact the Cascades after 6PM,
Central Oregon around 9PM, and beginning to spill into the
Columbia Basin around 11PM. Showers reach the Blue Mountains and
foothills around 3AM and linger into the early morning hours.
Outside of the Cascade and Blue Mountain zones, showers will be
intermittent as rain amounts of up to 0.04" are expected across
lower elevations of the Columbia Basin - most areas will
receive 0.02" or less. The NBM aligns with these amounts as it
highlights a 25-45% chance of measurable rainfall (0.01" or
greater) across lower elevations of the Columbia Basin. Rain
amounts of 0.08-0.15" are expected across the Cascade and Blue
Mountains, with higher terrain across the Washington Cascades
trending on the higher bound of the range and the Oregon
Cascades and Blue Mountains more toward the lower bounds of the
range. Snow levels will be hovering around 6000 feet, so the
only measurable snowfall will occur across the highest terrain
of the Cascade and Blue Mountains.

An upper level ridge follows closely behind the passing system
Thursday morning, bringing drier conditions and mostly clear
skies for the majority of the day. As a result, high
temperatures will bump up about 5 degrees from Wednesday to near
60 degrees across portions of the Columbia Basin. These
temperatures are about 5 degrees above average for this time of
year, and are expected to stay above normal into next week. The
next system, which is rather weak and well to the north, will
only clip the Washington Cascades. It does have significantly
more moisture than tonight`s system, but its passing through
Central British Columbia keeps measurable rainfall confined to
the Washington Cascades and east slopes. Snow levels will be
around 8000 feet, so rain is expected. Cle Elum is currently
along the gradient between a wetting rain (0.10" or greater),
with higher rain amounts of 0.2-0.3" possible west and at higher
elevations.

The parent system of this shortwave is forecast to
pass through Washington Saturday night through Sunday morning.
The proximity and orientation of this trough passage is expected
to extend rain chances across both the Oregon and Washington
Cascades, as well as the Blue Mountains. 54% of ensemble
clusters suggest little, if any, precipitation over lower
elevations of the Columbia Basin. Timing is trending slightly
slower as well, with 69% of members keeping precipitation
across the Cascades until early Sunday morning versus moving in
Saturday night. These differences are directly related to the
strength of the incoming system and the ridge that builds ahead
of it Friday afternoon/evening. The stronger trough relates to
a wetter and earlier scenario, with a stronger ridge more
efficient at weakening and slowing the incoming system.

A secondary concern with the weekend`s system will be related to
breezy conditions across Central and Eastern Oregon, primarily
focused on the Grande Ronde Valley. An incoming frontal system,
coupled with high pressure to the southeast and the potential
for cold-pooling in the Grande Ronde Valley will enhance winds
through this area. South winds of 20-30 mph with gusts of 40-50
mph will be possible as the GFS advertises a 4-5mb pressure
gradient between Baker and Meacham. Currently, the NBM suggests
a 35-65% chance of wind gusts reaching advisory-level criteria
of 45 mph or greater. This broad range leads to low confidence
in advisory-level winds occurring, at least related to current
guidance. In addition to the large range of NBM probabilities,
only 46% of ensemble members are suggesting a trend towards
higher winds for the Grande Ronde. This does seem quite low, but
it is likely the enhancement of cold pooling and a localized
pressure gradient is not being realized by these longer range
ensemble members. The arrival of shorter term guidance in the
next 24-48 hours will greatly improve confidence in this event.
75




&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
VFR conditions currently across all sites, which will stay the
course for most sites through the period. The only exception
will be reduced ceilings of 1500 feet at KDLS overnight. An
incoming system will drop ceilings to near MVFR for KPDT/KALW
as periodic light rain impacts all sites overnight. Winds will
stay light and below 10 kts for all terminals through the
period. Ceilings will improve and lift through the morning and
early afternoon. 75


&&

.Preliminary Point Temps/PoPs...
PDT  38  56  32  56 /  50  20   0   0
ALW  42  54  38  55 /  40  50   0   0
PSC  38  59  32  55 /  20  10   0   0
YKM  36  59  33  54 /  30   0   0  20
HRI  38  59  32  54 /  40  10   0   0
ELN  34  54  28  49 /  40   0   0  30
RDM  33  53  26  59 /  20   0   0   0
LGD  37  52  31  54 /  20  40   0   0
GCD  38  52  29  59 /  10  20   0   0
DLS  42  60  37  57 /  40   0   0   0

&&

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

&&

$$

DISCUSSION...75
AVIATION...75