128
FXUS66 KPQR 190601
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
1101 PM PDT Tue Aug 18 2026

Updated aviation discussion.

&&

.SYNOPSIS...Warm and dry conditions expected through much of
the week with morning clouds and afternoon clearing. Daytime
highs are expected to be in the 80s through the week. Winds
generally out of the west to northwest through Thursday,
strongest in the afternoon and along the Central Columbia River
Gorge and Upper Hood River Valley. Low chances for light showers
arrive Thursday night through Saturday, but conditions most
likely remain dry, along with 5-10% chance for evening
thunderstorms along the Cascades. Seasonable weather continues
late this weekend into early next week.

&&

.DISCUSSION...Tonight through Monday...The overall forecast
remains stagnant with little change to the forecast as predominately
dry and warm conditions continue through the week with minimal
impacts. The synoptic pattern through the mid-week remains
stagnant as a col will continue to dominate the Pac NW. This col
continues to be defined by a high over the Great Basin and a
low within the eastern Pacific. While there is a mirrored high
over the Gulf of Alaska and mirrored low over the central
provinces of Canada, these two systems are not as impactful as
the ones closer to CONUS. Overall, this pattern will support
continued onshore flow at the surface, which will maintain near-
normal daily high temperatures in the 80s within inland valleys
and 60s along the coast, and overnight lows in the 50s across
the region. With moist air flowing into the region, each night
will be characterized by marine stratus along the coast with
some stratus filtering into the I-5 corridor. These clouds
should clear out each afternoon as daytime heating progresses.
Expect light winds from the west/northwest for most places,
peaking each afternoon. An exception would be the Central
Columbia River Gorge and Hood River Valley, where west winds
will be strongest with gusts approaching 30-35 mph through the
evening.

The majority of ensemble members are in agreement that
aforementioned upper-level ridging over the Rockies and Great
Basin will start to dominate on Thursday and will result in a
brief warm up across the CWA. However, that warm-up will likely
be short-lived as ensemble guidance continues to show the eastern
Pacific low moves northeast-ward Thursday through Saturday.
This will bring a return of slightly cooler temperatures as well
as a southerly wind shift. This southeasterly flow is a
favorable pattern for precipitation as well as thunderstorms.
However, the overall atmosphere continues to remain dry, thereby
limiting the potential for any precipitation. But, models are
starting to show some general, elevated instability from
Thursday through Saturday. So, this will bear continue scrutiny
through the remainder of the week. It should be noted, that
there remains a lot of uncertainty as to the exact timing of the
Pacific low, as some ensembles have the low moving into the
region as early as Thursday evening, while others push it out
around 24 hours (Friday evening). To summarize the summary,
there is a 5-10% chance for elevated thunderstorms for the
Cascades from Thursday through Saturday, starting in the late
afternoon through the overnight hours each day.

Late this weekend into early next week, the trough weakens and
most ensemble members suggest a return of zonal flow before
another upper-level trough drops down from the Gulf of Alaska
and approaches British Columbia. At this point, there still
remains a fair amount of uncertainty with the exact magnitude
and placement of the late weekend/early next week trough. However,
this would suggest that onshore flow continues across the region
resulting in seasonable temperatures for late August. /42-10

&&

.AVIATION...Through 06z Thursday...VFR conditions inland with MVFR
stratus covering the coastal areas. Conditions are expected to
follow a similar pattern to the previous night with stratus moving
up the Columbia river into the Portland metro after 12z. Stratus
is a few hundred feet higher than last night sitting between
1000-1500 feet. Expecting mainly MVFR CIGs with this cloud layer
but could see brief drops below 1000 feet. Expect improvement back
to VFR for inland terminals between 16-18z and early afternoon
along the coast. Light overnight winds becoming northwest 5-10 kt.

KPDX AND APPROACHES...VFR conditions with mostly clear skies.
MVFR/IFR stratus expected to return after 12z Wed, improving to
VFR once again by 17-19z Wed. Northwesterly winds 4-7 kt. -19/03
&&

.MARINE...A largely stagnant pattern continues through much of
the week with high pressure offshore supporting northerly to
northwesterly winds of 8-15 kt and afternoon and evening gusts
up to 15-20 kt. Weak low pressure moving over the northeast
Pacific Friday into the weekend will shift winds out of the
south to southwest across the waters, but chances for gusts
exceeding 21 kt remain low, only 5% or less. High pressure and
northerly winds return by Sunday with a 30-50% chance of
northerly wind gusts exceeding 21 kts in the afternoon and
evening hours south of Cape Falcon. Seas of 3-6 ft persist
through the period. Increasing periods of 12-14 sec today and
Wednesday may result in a moderate risk for sneaker waves along
the coast. Caution should be used when in or near the water.
-03/10

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...None.

&&

$$

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