038
FXUS66 KPQR 181111 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
411 AM 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, strongest in the
afternoon and along the Central Columbia River Gorge and Upper
Hood River Valley. Spotty chances for light showers arrive
Friday night into Saturday, but conditions most likely remain
dry. Seasonable weather continues late this weekend into early
next week.

&&

.DISCUSSION...Today through Monday...Little change to the
forecast as predominately dry and warm conditions continue
through the week with minimal impacts. The large-scale pattern
remains stagnant through the period, with broad and relatively
flat upper-level ridging over the Rockies and Great Basin, and
broad upper-level troughing over the northeast Pacific. This
pattern will support continued onshore flow, maintaining 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 to 25-35 mph this afternoon.
Chances for wind gusts exceeding 35 mph today along the Central
Gorge are around 30-50%.

The majority of ensemble members are in agreement that upper-
level ridging over the Rockies and Great Basin will build late
in the workweek, which would favor a brief warm-up on Thursday.
However, that warm-up will likely be short-lived as ensemble
guidance continues to show the upper-level trough over the
northeast Pacific shifting onshore Friday into the weekend,
resulting in slightly cooler temperatures and winds coming from
the south/southwest. There remains spotty chances (10-25%) for
showers across portions of the Coast Range and Cascades, but the
overall airmass will remain too dry to support accumulating
rainfall from a weak front. 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 uncertainty with the exact
magnitude and placement of the trough. However, this would
suggest that onshore flow continues across the region with
seasonable temperatures for late August.        -10

&&

.AVIATION...Through 12z Wednesday...Satellite imagery and terminal
observations as of early Tuesday morning depicts marine stratus
along the coast bringing LIFR/IFR conditions to KAST and KONP.
This stratus is pushing through gaps in the Coast Range and up the
Lower Columbia River, and is expected to reach the Portland Metro
Area by 12-14z Tue. Observations along the coast and the Cowlitz
Valley (KKLS) show the base of the stratus deck around 400-800 ft,
so expect IFR conditions at KPDX/KTTD once the stratus arrives. Low
confidence for stratus making it into the central/southern
Willamette Valley, as guidance suggests a 15-25% chance for IFR/MVFR
CIGs at any given hour between 12-17z Tue.

High confidence for stratus dissipating from the Willamette Valley
after 17-18z Tue, returning VFR conditions through the rest of the
TAF period. Along the coast, there is a 30-50% chance for brief
improvement to VFR at any given hour between 21z Tue-00z Wed before
IFR/MVFR stratus returns in the evening. Westerly to northwesterly
winds across all terminals around 4-8 kt, peaking this afternoon
with gusts up to 18 kt along the coast.

KPDX AND APPROACHES...IFR stratus arriving around 12-13z Tue and
lasting through 17-18z Tue. After 18z Tue, daytime heating will
dissipate stratus and return VFR conditions through the rest of the
TAF period. Northwesterly winds 4-7 kt.    -10

&&

.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 gusts up to 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. 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.        -10

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

www.weather.gov/portland

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