408
FXUS66 KPQR 130441 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
841 PM PST Wed Nov 12 2025

Updated Aviation Discussion

&&

.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...A warm front is slowly pushing northward across the
airspace through the overnight hours. This front will bring
generally VFR conditions with light rain. Could see areas of
intermittent MVFR conditions across the airspace through the
period. Rain will continue behind the front on Thursday. Heavier
precipitation could briefly lower conditions to MVFR/IFR from
18Z Thursday through at least 06Z Friday.

Winds generally light and variable for most inland locations
through the TAF period. However, there will be southerly winds
along the coast, with gusts up to 25 kt from 20Z Thursday through
03Z Friday. Also, elevated east winds through the Columbia River
Gorge with gusts up to 20 kt at or near KTTD through 06Z
Thursday. Afterwards, winds expected to subside below 10 kt.

KPDX AND APPROACHES...Generally VFR with variable winds under 5
kt and light rain expected through the period. /42

&&

.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.

&&

$$

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