497
FXUS66 KPQR 240444 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
944 PM PDT Sun Aug 23 2026

Updated Aviation Discussion

.SYNOPSIS...Upper level ridging and low-level offshore flow
develops Monday, continuing into Tuesday, bringing warmer and
sunnier conditions with high temperatures in the mid 80s to
lower 90s across the interior lowlands, warmest on Monday.
Wildfire smoke will also begin to increase over the Columbia
River Gorge, Upper Hood River Valley, and the greater
Portland/Vancouver metro area Monday morning and then linger
through Tuesday; however smoke is not expected to be dense for
most locations. Onshore flow arrives by Wednesday and continues
thereafter, which will clear any lingering smoke out of the area
and bring relatively cooler temperatures through the end of the
week and into the weekend.

&&

.DISCUSSION...Tonight through Saturday Night...Water vapor satellite
imagery reveals the upper level shortwave trough lifting across NE
Washington into Canada this afternoon. Heights aloft will continue
to increase through tonight allowing for clearing skies. As a ridge
of high pressure builds aloft over the region, a surface thermal
trough develops along the coast extending into western WA early
Monday morning. This will allow for light offshore flow to develops,
especially over the western slopes of the Cascades with east winds
increasing through the Columbia River Gorge later Monday morning.
Winds are not expected to be very strong, but gusts up to 25-30 mph
will certainly be possible through the western gorge. Temperatures
at 850 mb are also expected to rapidly rise to around 20C by Monday
evening. Downsloping winds and afternoon mixing will therefore allow
for surface temperatures to warm into the upper 80s to lower 90s
across much of the inland lowlands, as well as through Cascade
valleys, while temperatures at the coast will likely warm into the
70s before winds shift as sea-breezes occur early in the afternoon.
This offshore flow will also cause wildfire smoke to begin to filter
back down into the valleys, including into the Portland/Vancouver
Metro area, Columbia River Gorge and Upper Hood River Valley.
However, smoke is not expected to be dense for most locations.

By Monday evening, the surface thermal trough is expected to shift
east into the Willamette Valley, and potentially to the Cascade
crest, allowing for onshore flow to return across much of the area.
Lingering low pressure in the valley will likely allow for very
light offshore flow to return over the Cascade foothills Monday
night into early Tuesday. This will likely maintain elevated
overnight temperatures in the lower to mid-60s where the easterly
winds persist. A moderate risk of heat related illnesses will
therefore exist Monday into Tuesday. Wildfire smoke is also likely
to linger into Tuesday as well for northern portions of the forecast
area.

Early Tuesday, a shortwave trough will lift just offshore, skirting
the coast, as a deeper upper level low in the Gulf of Alaska drops
south. This should cause a southerly wind reversal to occur along
the Oregon coast and into the Willamette Valley. Heights aloft still
remain high with the axis of the upper level ridge over the
Intermountain West, but 850 mb temps cool to around 16-17C. Still
expecting Tuesday temperatures to warm into the mid to upper 80s
(about 4-8 degrees above normal). By Tuesday evening, surface high
pressure building along the coast will bring a strong marine push of
westerly winds. Any lingering wildfire smoke should shift back east
of the Cascades by Wednesday.

Models and their ensembles are showing fairly good agreement that
the upper level trough over the NE Pacific gradually pushes east
over the Pacific NW Wednesday through Thursday, with troughing
likely persisting over the region through the end of the week and
into the weekend. There is high confidence that temperatures trend
cooler to near or slightly below average. Confidence is low
regarding precipitation, if any will occur later this week. But, if
any rain does fall, it would most likely be very light. Best chances
would be drizzle along the coast with a weak frontal passage
Thursday morning; and again on Saturday, but PoP remains around 15%
or less. /DH

&&

.AVIATION...06Z TAFs...Generally VFR conditions under mostly
clear skies across the airspace through around 15Z Monday. Coastal
locations could see some MVFR to LIFR conditions developing along
the coast from 08Z-18Z Monday, with higher probabilities of
IFR/LIFR conditions impacting KONP. Could also see some MVFR
conditions developing between KSLE and KEUG through the same time,
but there is only a 10-25% chance of this occurring. Any lowered
flight conditions should develop into VFR around 16Z-18Z Monday.

North/northeast winds through the TAF period. Expect breezy winds
gusting around of 20 kt at KONP. Around 18-20Z Monday, easterly
winds around 8-11 kt are expected to develop at KTTD and KPDX as
offshore winds develop through the Columbia River Gorge. The
north/northeast winds will also push some wildfire smoke/haze into
the Willamette Valley.

Smoke/haze will have the potential reduce vertical and slantwise
visibilities at times. In addition, temperatures are expected to
warm into the lower 90s Monday afternoon at the inland TAF sites,
so be aware of high density altitude which may reduce aircraft
performance.

KPDX AND APPROACHES...Generally VFR flight conditions through the
TAF period. North/northeast winds through the TAF period with more
easterly winds developing around 18-20Z Monday. Expect 8-11 kt
to develop near and east of the terminal as easterly winds
develop through the Columbia River Gorge. Smoke/haze will have the
potential reduce vertical and slantwise visibilities at times. In
addition, temperatures are expected to warm into the lower 90s
Monday afternoon at the inland TAF sites, so be aware of high
density altitude which may reduce aircraft performance. /42

&&

.MARINE...Northerly winds will gradually increase Sunday
afternoon and evening as high pressure strengthens over the
northeast Pacific. Gusty winds will develop over the waters,
increasing from south to north from Florence to Cape Shoalwater.
Wind gusts up to 25 kt are expected to develop Sunday evening
over the southern and central waters, and over the northern
waters Sunday night. These wind speeds will then persist through
Monday afternoon/early evening before decreasing Monday night.
Small Craft Advisories remain in effect from 5 PM Sunday to 5 PM
Monday for the coastal waters from Florence north to Cape
Falcon and from 11 PM Sunday to 8 PM Monday for the coastal
waters north of Cape Falcon to Cape Shoalwater. Gusty north
winds up to 25 kt are also expected for the Columbia River Bar
starting at 8 AM Monday, which also has a Small Craft Advisory
in effect.

A southerly wind reversal arrives early Tuesday morning over the
inner waters with gusts up to 15-20 kt expected by Tuesday
afternoon. This will also bring increasing chances for marine fog
beginning early Tuesday morning, especially over the inner
waters. Visibilities may fall below 1 SM at times as the southerly
winds develop and upwelling occurs. Aside from the increasing
winds and potential marine fog, significant wave heights look to
remain relatively low at around 3 to 5 ft through Friday. -23

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 8 AM to 8 PM PDT Monday for PZZ210.

     Small Craft Advisory until 8 PM PDT Monday for PZZ251-271.

     Small Craft Advisory until 5 PM PDT Monday for PZZ252-253-272-
     273.
&&

$$

www.weather.gov/portland

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