218
FXUS66 KPDT 081157
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
457 AM PDT Mon Jun 8 2026

.KEY MESSAGES...

- Widespread rain today, heaviest over the Cascade and Blue
  mountains

- Breezy to windy today through Wednesday, strongest on Tuesday

- Warmer, drier weather late week through the weekend

&&

.DISCUSSION...
Water vapor imagery shows a closed mid/upper-level low rotating
in the Gulf of Alaska this morning. Meanwhile, a shortwave is
evident southeast of the low, diving towards the Pacific
Northwest. 00Z ensemble NWP guidance is in excellent agreement
that the shortwave will move inland later this afternoon through
tonight, ushering in widespread shower chances. For the lower
elevations, precipitation totals are currently forecast to be
light (a few hundredths of an inch to a couple tenths of an
inch) while the mountains will see higher precipitation amounts
of several tenths of an inch (Blues) to locally over an inch
(Cascades, especially in Washington).

Ahead of the precipitation, warm temperatures in the 70s coupled
with locally breezy winds and low relative humidity in the teens
to lower 20s are forecast for roughly the eastern half of our
area of responsibility. Elsewhere, cooler temperatures and
higher relative humidity are expected beneath thicker cloud
cover and/or in light rain.

Per latest 00Z NWP guidance, breezy southerly to southwesterly
850-hPa winds of 15-35 kts are expected (90 percent confidence)
to overspread the region this afternoon, becoming southwesterly
to westerly and increasing in magnitude to 35-55 kts overnight
through Tuesday morning, then becoming westerly to northwesterly
and slackening to 25-40 kts Tuesday afternoon and 15-25 kts on
Wednesday.

NBM probabilities of exceedance suggest very high (80-99
percent) chances of reaching or exceeding advisory-level wind
gusts (45 mph or greater) 11 PM PDT tonight (Monday night)
through 11 PM PDT Tuesday across the foothills of the Blue
Mountains, north-central Oregon, the Simcoe Highlands, and
through the Kittitas Valley and eastern Columbia River Gorge.
Forecaster confidence in these probabilities is a little lower
(70-90 percent) based on the timing of the strongest winds aloft
not coinciding with peak mixing (i.e. strongest winds are at
night), but forecast cross-Cascade pressure gradients are
sufficiently strong (8-12 hPa difference between PDX and GEG)
Tuesday afternoon to support wind headlines. Will note the NBM
indicates a low (20-40 percent) chance of reaching warning-level
wind gusts (58 mph or greater) for our most wind-prone
locations.

The remnants of the aforementioned low in the Gulf of Alaska
are expected (80-90 percent confidence) to slide over the
Pacific Northwest late Tuesday through Wednesday, resulting in
continued mild temperatures and rain showers (mainly for the
mountains). Weak instability (CAPE of up to a couple hundred
J/kg) coupled with forcing from the shortwave may facilitate an
isolated thunderstorm over the eastern mountains Tuesday
afternoon, but chances are low (5-15 percent).

Warmer, drier conditions are then forecast Thursday through the
weekend as an upper-level ridge of high pressure will likely
(80-90 percent confidence) build offshore in the Pacific and
eventually shift east into the Pacific Northwest. Ensemble
cluster analysis reveals some differences in the amplitude and
location of the ridge through the weekend, and a low (10-20
percent) chance of a cooler, wetter pattern with the ridge axis
located well offshore and shortwave troughing digging into the
Pacific Northwest from the north.

While outside of the current forecast period, temperatures are
forecast to peak on Monday, with a 50-80 percent chance of >=
90 degrees, and 5-15 percent chance of >= 100 degrees for the
lower elevations. Moreover, probabilistic HeatRisk guidance
indicates a 15-40 percent chance of Major (level 3 of 4)
HeatRisk for the majority of the lower elevations within the
greater Columbia Basin region on Monday. This level of heat
affects anyone without cooling/hydration.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
VFR conditions are forecast for all sites through the period. An
incoming low-pressure system will bring light rain to all
terminals by afternoon or evening. MVFR CIGs are not forecast,
but cannot rule them out (5-30 percent confidence, highest at
YKM). Winds will become breezy later today, especially overnight
into Tuesday morning when gusty winds are likely (90 percent
confidence), but confidence in exact timing/magnitude of winds
at terminals is low (30 percent).

&&

.Preliminary Point Temps/PoPs...
PDT  71  48  68  43 /  20  90  40   0
ALW  75  52  67  47 /   0  90  60  30
PSC  75  49  73  44 /  20  90  30   0
YKM  70  48  71  42 /  50  80  10   0
HRI  73  48  71  44 /  20  80  20   0
ELN  66  45  64  39 /  50  90  40   0
RDM  64  43  65  32 /  80  60  10   0
LGD  71  46  63  41 /   0 100  80  20
GCD  70  44  66  37 /  40 100  40  10
DLS  68  53  68  49 /  80  90  30   0

&&

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

&&

$$

DISCUSSION...86
AVIATION...86