627
FXUS66 KPQR 181749
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
1049 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 18z Wednesday...Marine stratus that pushed
down the Upper Columbia River into the Portland metro area is
dissipating as of 1730z Tue with VFR conditions and clear skies
expected for all inland areas by 18-20z. Expecting MVFR/IFR
conditions to form in the SW WA lowlands and Portland metro area
south to KAST between 12-15z Wed, once again improving to VFR by
17-19z Wed. The coast remains socked in with marine stratus.
Predominately MVFR/IFR conditions are expected along the coast
over the next 24 hours, though there`s a 20-30% chance terminals
could briefly become VFR at any hour between 19z Tue - 02z Wed.
There`s also a 60-90% chance of LIFR conditions returning at any
hour 00-18z Wed. Westerly to northwesterly winds across all
terminals around 4-6 kt, peaking this afternoon and evening up to
8-10 kts before decreasing once again overnight.


KPDX AND APPROACHES...Stratus is dissipating with VFR conditions
with mostly clear skies expected after 18z Tue. MVFR/IFR stratus
expected to return after 12z Wed, improving to VFR once again by
17-19z Wed. Northwesterly winds 4-7 kt. -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 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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