309
FXUS66 KPDT 021004
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
304 AM PDT Tue Jun 2 2026

.KEY MESSAGES...

- Warming trend peaks today, cooling through remainder of week.

- Mountain showers and isolated thunderstorms Wednesday.

- Breezy afternoon winds Wednesday through Saturday.

&&

.DISCUSSION...
Current radar and infrared satellite imagery shows dry
conditions as high level clouds linger across the Columbia
Basin. These clouds are associated with the remnants of an
upper level low pressure currently over southern Saskatchewan,
which will weaken and move east as a weak transient ridge passes
over the Pacific Northwest. This will provide clearing skies
through the morning as afternoon temperatures reach into the low
to mid-80s across the Columbia Basin, Central Oregon, Columbia
Gorge, Blue Mountain foothills, and the Yakima/Kittitas Valleys.
These high temperatures are about 5 degrees above normal for
this time of year. Several systems are poised to pass through
the area over the weekend, cooling highs to near normal values
Thursday and below normal over the weekend.

An incoming upper level shortwave, extending from a strong
upper level low pressure system located in the Gulf of Alaska,
will allow for increasing cloud cover tonight ahead of a 25-45%
chance of afternoon showers across Cascades, John Day Highlands,
Blue Mountains, and Wallowas - with best chances residing
across the Washington Cascades and east slopes. The incoming
shortwave does erode the weak, transient ridge to allow for a
10-20% chance of isolated afternoon thunderstorms across Grant,
Crook, Union, Wallowa, and southern Umatilla counties. The HREF
highlights mean surface CAPE of 200-400 J/kg, as multiple
members suggest isolated storm initiation around 1 PM. Low level
shear is favorable between 30-35kts, but lapse rates are
expected to decrease to below 6C/km by mid-to late afternoon,
which should keep any developing storm cells sub-severe and
isolated in nature.

The initial passing of the shortwave trough Wednesday will
allow for a pressure gradient to develop along the Cascades,
causing breezy afternoon/evening conditions through the Simcoe
Highlands, Columbia Gorge, north-central Oregon, Blue Mountain
foothills, and the Yakima/Kittitas Valleys. Sustained winds of
20-25 mph and gusts of up to 40 mph will be possible across
these areas. The NBM advertises a 60-80% chance of 40 mph gusts
or more across the Simcoe Highlands and north-central Oregon,
with a 25-35% chance through the Kittitas Valley. The parent
upper level low over the Gulf of Alaska will slowly meander
south along the coast of British Columbia, reaching the
Washington coast Friday before passing through the area on
Saturday. This is expected to produce an even stronger pressure
gradient across the area, potentially leading to advisory-level
(45+ mph) wind gusts across the Simcoe Highlands and north-
central Oregon as the NBM suggests a 60-80% chance of occurrence.
However, uncertainty is present in the low`s strength and
timing, which is indicated by a slight majority (51%) of
ensemble members which show a weaker or slower incoming system.
This outcome would lead to a more relaxed pressure gradient
developing along the Cascades, resulting in lower wind potential
both Friday and Saturday. 75


&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
VFR conditions currently across all sites, which will stay the
course through the period. Winds will stay light and at or below
10 kts as 25kft ceilings develop by late evening. 75

&&

.Preliminary Point Temps/PoPs...
PDT  81  50  78  49 /   0   0   0  10
ALW  81  55  81  54 /   0   0   0  10
PSC  85  53  84  53 /   0   0   0   0
YKM  84  56  81  50 /   0   0  20  10
HRI  84  52  81  51 /   0   0   0   0
ELN  79  52  76  47 /   0   0  40  10
RDM  82  50  74  39 /   0   0  10   0
LGD  79  47  78  46 /   0   0  20  30
GCD  83  47  78  42 /   0   0  20  10
DLS  87  62  78  55 /   0   0  10   0

&&

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

&&

$$

DISCUSSION...75
AVIATION...75