343
FXUS66 KPQR 122249
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
249 PM PST Wed Nov 12 2025

.SYNOPSIS...Typical fall rainy weather through Sunday with
minimal breaks and seasonable temperatures. While rainy, no
hydrological impacts expected. The next pattern of concern
arrives early next week when we have the chance to see a cool
down with Cascade Pass snow.


&&

.SHORT TERM...Now through Saturday...Today has been a great
example of fall weather in the Pacific Northwest. Showers
continue to pop up on radar but due to dry air at the surface,
most of the rain is evaporating before reaching the ground. Wind
has been a feature of notice today with gusty conditions within
the Columbia River Gorge. Ended up increasing easterly winds and
gusts within the Gorge, especially around Troutdale, due to the
forecast pattern. Looking at pressure gradients from Troutdale
to the Dalles combined with the incoming temperature gradient,
we are looking at values around -4 mb. This would coincide with
gustier conditions than the mean of the NBM was providing.
Therefore trended towards the 90th percentile for wind in the
Gorge and outflow areas.

The big feature of concern in the short term forecast is a
closed low pressure system sitting off the coast of the
California and Oregon border. This low is ushering in warm air
from the tropics. While a bulk of the impacts of this low will
be over California, we will still see the wrap around warm front
and moisture. Models are in good agreement in the overall track
of this low but there does remain a slight spread. If the low
were to move further north we would be wetter with more wrapped
around cold air. Widespread rain is expected to start this
evening and persist through Thursday with nearly a 90-100%
chance of accumulating precipitation everywhere in our forecast
area. Diving into some of the heavier accumulation
probabilities, lets look at 0.5". Along the coast, Coast Range,
and the Cascades there is around a 75-85% chance of 0.5", and
around a 30-50% chance within the Willamette Valley over the
next 24 hours. The 90th percentile (meaning a 10% chance), shows
around 1.7-2.0" along the Coast and Coast Range, and around
0.75-0.85" inland. Overall the spread of rainfall totals will
depend on the track of the low and whether or not we see more of
the impacts from the warm frontal system down south.

Rain will persist through Friday as the low shifts southward.
Warm air will linger over the area but a brief area of cooler
air settles in. This airmass has warmed though over the last few
forecast cycles so, while snow was previously expected at pass
level, that is no longer the case. Snow levels have risen
considerably on Friday and impactful snow is no longer expected.
On Saturday, ensembles show a slightly drier shift as we sit in
an inverted trough. Nearly half of the models show some
resemblance of rain while the other half are keeping conditions
drier. Higher probability of rain along the coast with some
rain shadowing inland. Overall, expect typical fall weather for
the next three days. -27

.LONG TERM...Saturday Night through Wednesday...Conditions will
remain showery on Saturday night into Sunday morning but then
conditions will quickly shift Sunday night. A cold air wrapped
low aloft will move over British Columbia extending a long wave
trough over the region. This trough has a band of enhanced
vorticity advection, moisture, and potentially breezy winds.
Accumulating rain will be less on Sunday but will ramp up
through Monday as the trough intensifies and a closed low forms
at the base. This forming low will wrap even more cold air
behind it causing temperatures to drop. At 850 mb, temperatures
will reach freezing by late Monday morning and continue to lower
through late Tuesday night. At the surface this trend will be
coupled causing snow levels to fall to around 3500 ft. With this
current pattern there will be pass level snow. However, if the
low advects further north then the colder air may not filter in
as far south and thus we would miss enough of the cold effect
for snow to form.

While snow in the passes is one component to look at, surface
temperatures too will cool on overnight into Tuesday morning.
While freezing temperatures (32 deg F or 0 deg C) are not
expected to be widespread in the lowland, the probability is not
zero. In the outskirts of Eugene/Corvallis there is around a
20% chance of freezing temperatures less than a 10% chance for
the northern Willamette Valley and less than a 5% chance for the
coast. In the Upper Hood River Valley these probabilities are
closer to 60%. Similar chances are observed through Wednesday
morning, though the Willamette Valley north of Albany will see
slightly lower chances. Will say though that the pattern in the
long term is very messy and therefore there is ample room for
forecast change - similar to what we have seen with this
upcoming cooler air mass. -27

&&

.AVIATION...At 22z Tue, a warm front is pushing north into Lane
and Lincoln Counties in central OR. This front will continue
moving north over the next few hours with -SHRA or -DZ
accompanying it, moving into central WA by 03-05z Wed. As the
front moves over terminals still reporting MVFR/IFR CIGs and VIS
due to stratus, it will cause enough mixing to improve conditions
to VFR high mid/high level clouds. Periods of rain will continue
behind the front through Thursday. Heavier showers could lower
conditions to MVFR/IFR CIGs or VIS, though these conditions are
not expected to become more widespread until after 21z Thu-00z
Fri. Winds generally light and variable across the region for
most of the TAF period, except for brief southerly winds along the
coast through 00-03z Thu with gusts up to 20-25 kts as the front
passes through. Also, east winds are gusty through the Columbia
River Gorge, bringing gusts up to 20-25 kts at KTTD through 00-03z
Thu then again after 09z Thu.

KPDX AND APPROACHES...VFR with light and variable winds under 5 kt
expected through the period. Rain showers begin after 00-03z Thu.
-03

&&

.MARINE...A front associated with a low pressure system in the NE
Pacific is moving north through the waters Wednesday afternoon
and evening. South winds 15-20 kts with gusts up to 20-25 kts are
expected with the frontal passage. Seas will build to 9-10 feet at
13-15 seconds by early Thursday morning. Winds briefly turn
easterly and ease to around 20 kt or less Wednesday night,
though winds will quickly increase and turn southerly again on
Thursday as the low deepens and swings another front through the
waters. Will note that occasional gale-force wind gusts of 34 kt
or greater are possible between 10 AM and 4 PM Thursday, mainly
south of Cape Falcon and beyond 20-30 NM. There`s also a 10-20%
chance of storm force wind gusts of 55 kts or greater in this
area. This area will also have a 40-50% chance for seas building
above 15 ft. The Small Craft Advisory for all marine zones remains
in effect through 4 AM Friday.

Another frontal system will swing through British Columbia and far
northwest Washington on Friday, maintaining relative breezy
southwesterly winds over our coastal waters. There`s a 60-75%
chance of wind gusts stronger than 21 kt with this front.
-10/03

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory until 4 AM PST Friday for PZZ210-251>253-
     271>273.
&&

$$

www.weather.gov/portland

Interact with us via social media:
www.facebook.com/NWSPortland
x.com/NWSPortland