342
FXUS66 KPQR 302100
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
200 PM PDT Sun Aug 30 2026

Updated marine and aviation discussions.

&&

.SYNOPSIS...High pressure will result in dry and warm
conditions across the area today and Monday. A significant
pattern change begins on Tuesday with a return of cooler
temperatures, rain, and breezy southerly winds through the end
of the week. Wednesday and Thursday are expected to be the
wettest days with also a 10-20% chance for thunderstorms.
Conditions trend slightly drier over the weekend, but there
remains chances for lingering showers.

&&

.SHORT TERM...Today through Tuesday Night...Satellite imagery
and surface observations as of late Sunday morning depicts
mostly sunny skies across the area with some scattered clouds
across southwest Washington and far northwest Oregon. Will
maintain dry and warm conditions today and Monday as shortwave
ridging sets up over the Pacific Northwest. Expect afternoon
highs in the mid to upper 70s today across interior valleys, and
60s along the coast. Tomorrow will be the warmest day of the
week as the ridge reaches its peak amplitude, with highs warming
up into the mid 80s across interior valleys. This dry and warm
weather will be short-lived as we head into a significant
pattern change beginning Tuesday.

Monday night into Tuesday, the aforementioned ridge will weaken
and get pushed eastward as the first of two upper-level troughs
drops down from the Gulf of Alaska. This trough will track
towards southern Oregon and northern California, bringing
increased cloud cover and a 25-50% chance for light showers.
This will support cooler temperatures across interior valleys,
with Tuesday afternoon highs falling into the low to mid 70s.
Winds will also begin to turn out of the west/southwest,
generally remaining light with gusts below 20 mph. An exception
would be the Columbia River Gorge and Hood River Valley, where
westerly gap winds Tuesday afternoon could gust to 25-35 mph
with a 30-50% chance for maximum gusts exceeding 40 mph. -10


.LONG TERM...Wednesday through Saturday...Wednesday into
Thursday will be the more significant soaker days as the
majority of ensemble members are showing a second, much deeper
upper-level trough dropping down into the Pacific Northwest. The
associated surface front swings through on Wednesday, bringing
widespread rain, cooler temperatures, and breezy winds from the
south. In addition, there will be a 10-20% chance for
thunderstorms. Chances for exceeding 1 inch of rain in 48 hours
between 5 AM Wednesday to 5 AM Friday are high (70-90%) across
northwest Oregon and southwest Washington, with the highest
chances along the coast, Coast Range, and Cascades. Chances for
exceeding 2 inches during this same timeframe are around 30-50%
for these higher terrain features, and 5-15% along the I-5
corridor. Orographic enhancement will play a big role with
providing higher rainfall amounts to the mountains.

Thursday afternoon to Saturday, the upper-level trough remains
over the Pacific Northwest and we transition into a post-frontal
environment with lingering showers. Given that there will be
cooler air aloft, this will favor increasing atmospheric
instability and thus chances for thunderstorms. There will be
another 10-20% chance for thunderstorms on Thursday following
the initial frontal passage. Any passing thunderstorms may
produce lightning, heavy rain, erratic winds, and small hail.
Overall, while the upcoming rain will not quite yet be a "fire
season ender," it will definitely slow down fire season and help
put a damper on ongoing wildfires. -10

&&

.AVIATION...Through 00z Tuesday...VFR conditions favored across
the airspace throughout the period. Sct-bkn low clouds linger
across far northwestern OR and southwestern WA per satellite
imagery as of 21z Sun, with largely clear skies elsewhere. North
to northwest winds of 5-10 kt inland and 10-15 kt with gusts as
high as 20-25 kt along the coast and in the southern Willamette
Valley this afternoon will ease to 5 kt or less after 03-06z
Mon. Light offshore (north to northeast) flow overnight will
limit chances for MVFR cigs beneath low clouds to 20-30% along
the coast and in the Willamette Valley.

KPDX AND APPROACHES...VFR conditions expected throughout the
period. Coverage of lingering low clouds will not restrict cigs
this afternoon. Northwest winds of 5-10 kt will ease below 5 kt
tonight, with low chances, only 10% after 09z Mon, for MVFR cigs
if low cloud coverage is higher than expected overnight. -36

&&

.MARINE...Transient ridging over the Northeast Pacific will see
northerly to northwesterly winds continue into Tuesday morning.
Thermal troughing along the coast will yield strengthening near-
shore winds Monday afternoon, reaching 15-20 kt with gusts to
25 kt within 10-20 NM north of Cape Falcon and including the
Columbia River Bar, where a Small Craft Advisory has been
hoisted from 2 PM to 8 PM PDT Monday afternoon and evening.
Largely wind-driven seas will persist at 4-6 ft during this
period.

On Tuesday, winds back out of the south-southwest as a broad
pattern shift sees troughing develop over the Northeast Pacific
while ridging moves inland. By Wednesday, a robust frontal
system will traverse the coastal waters of OR/WA. Southerly
winds ahead of the frontal passage are likely (50-75% chance) to
yield at least intermittent gale-force gusts. Sustained winds
are less likely (30-60% chance) to reach gale- force, with
higher chances generally to the north and closer to shore. Gale
Watches may be needed if confidence persists in the duration of
potential gusty winds across enough of the coastal waters. These
strong winds will also see seas build to 8-12 ft, with chances
for significant wave heights to reach 15 ft remaining less than
10%. Behind this system, winds and seas should ease from late in
the week into next weekend. -36

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 2 PM to 8 PM PDT Monday for PZZ210-
     251.

&&

$$

www.weather.gov/portland

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