484
FXUS66 KPQR 240411 AAA
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
811 PM PST Sun Nov 23 2025

Updated Aviation discussion

.SYNOPSIS...A weak front will maintain light scattered showers
and drizzle across northwest OR and southwest WA this afternoon.
Tonight, temperatures cool down behind this system, dropping
snow levels to 2500-3500 ft, resulting in light snow showers
through the Cascade passes. Shower activity decreases on Monday,
but can`t rule out some isolated lingering showers. The next
system arrives Tuesday-Wednesday, returning widespread rain. Wet
weather continues through the end of the week, with potential
for much colder temperatures this weekend.

&&

.SHORT TERM...Today through Tuesday Night...Radar imagery as of
early Sunday afternoon depicts light scattered showers/drizzle
across northwest OR and southwest WA as a weak front progresses
through the region. Rainfall amounts so far in the last 24 hours
have generally been less than 0.10" for most places, however,
higher amounts of 0.20-0.40" have been observed along the north
OR and south WA coasts, and interior southwest WA. This weak
front will continue to push southeastward, spreading light
showers/drizzle to the southern Willamette Valley and Linn/Lane
County Cascades this afternoon. Some drizzle may lead to slight
visibility reductions, so make sure to use slow down and leave
plenty of distance ahead of you if you`re driving.

Shower activity gradually decreases this evening as the front
exits the region. Southerly winds will turn more westerly behind
the front, but generally remain light for most places. The
breeziest areas will be the high Cascades and eastern Columbia
River Gorge where westerly winds could gust up to 25-30 mph.
Temperatures will also cool down behind this system, making for
a chillier Monday morning with snow levels dropping below pass-
level (2500-3500 ft). Remaining showers in the Cascades tonight
into early Monday morning would fall as snow, with snow amounts
forecast under 1" through the passes. Chances for snow amounts
exceeding 1" tonight are around 30-40% for Highway 26 and
Santiam Pass, and about 5% for Willamette Pass.

Will maintain a 20-40% chance for lingering showers on Monday,
but drier conditions return by Monday night as a shortwave ridge
builds over the Pacific Northwest ahead of the next system.
Tuesday morning will be the chilliest night of the week, with
low temperatures forecast to drop into the low to mid 30s across
interior lowland valleys. With moist surface conditions, there
will be potential for frost development early Tuesday morning,
especially over grasses and elevated metal surfaces in
outlying, rural areas. One factor that could inhibit frost
development is cloud cover. Model soundings show that there will
mainly be high clouds, so if these high clouds end up being too
thick, then radiational cooling may not be as efficient for
frost formation.

By Tuesday afternoon, ensemble guidance suggests that upper
level ridging will build over the U.S. West Coast, however, the
Pacific Northwest appears to be right at the top of the ridge.
While 500 mb heights will climb and bring relatively warmer
temperatures, we will be far from dry. The next system will
ride the periphery of the ridge and enter the Pacific Northwest,
returning widespread rain chances Tuesday afternoon through
Wednesday. Since this would be a warmer system with 850 mb
temperatures around 2-4 deg C, snow levels will climb above 6000
ft and result in rain over the Cascade passes. Conditions
remain showery through Thursday as this system moves through the
region. Chances for 48-hour liquid precipitation exceeding 1"
from 4 AM Tue to 4 AM Thu are around 40-70% along the coast,
Coast Range, Willapa Hills, and Cascades (highest chances
further north, lowest toward Lane County), 15-30% across the
Willamette Valley and Upper Hood River Valley, and 30-50% across
the southwest WA lowlands.          -10

&&

.LONG TERM...Wednesday through Saturday...The majority of
ensemble members favors the potential for wet weather
continuing through the end of the week. Ensembles show another
system arriving Thursday, but there is uncertainty with the
exact track and magnitude of the system, thus bringing
uncertainty with precipitation amounts. Chances for 48-hour
liquid precipitation exceeding 1" from 4 AM Thu to 4 AM Sat are
around 30-50% along the the coast, Coast Range, Willapa Hills,
and Cascades and 5-15% across interior lowland valleys.

By Friday, about 65% of ensemble members (mostly from the GEFS)
show 500 mb heights falling across the region, suggesting that
temperatures will begin to cool down as broad troughing drops
down into the Pacific Northwest. There remains high uncertainty
with the magnitude and track of this broad trough, but will
likely maintain precipitation chances with this set-up. By
Saturday, about 80%+ of members are showing below-average 500 mb
heights across much of the Western U.S. This is hinting at a
more significant cooldown heading into the weekend, but by how
much is to be determined.

You may notice in late in the forecast period (Saturday night
into Sunday morning) that there is a mention of a rain/snow mix
in the lowlands, including the Willamette Valley and southwest
WA lowlands. While this is possible, probabilities for this
outcome to occur are very low (1-5%). In addition, overall model
spread is very large for both temperatures and precipitation
amounts. This means forecast confidence is very low, however,
we`ll be taking a closer look at this over the next few days.
Even if a rain/snow mix does occur, accumulating snow and travel
impacts in the lowlands would be highly unlikely.      -10

&&

.AVIATION...Southwest flow aloft turns northwesterly as an upper
level trough moves over the region tonight. Light rain associated
with a front will continue to push east of the area this evening,
with most precipitation ending by 06z. A mix of IFR, MVFR and VFR
flight conditions are expected to persist through 12-14z Monday.
Another weak front may bring some light showers to northern
portions of the area later Monday morning through the afternoon.
This will likely maintain a mix of MVFR and VFR conditions north
of KSLE, while areas to the south are more likely (80% chance) to
see predominately VFR conditions.

KPDX AND APPROACHES...The front is pushing east of the area with
conditions improving slightly as light rain has mostly ended. LIFR
to IFR cigs are likely to continue through at least 06z, with
around a 40% chance of IFR cigs persisting through 12z Monday.
Conditions likely improve to a mix of MVFR and VFR through much of
the day Monday. Highest chances for MVFR between 14-18z Monday
(60% chance). Another weak front possible Mon afternoon.  /DH

&&

.MARINE...Seas will remain around 10 to 14 ft through Sunday night
before falling to 8 to 9 ft by Monday afternoon and then 6 to 8
ft on Tuesday. The next frontal passage arrives Tuesday night
into Wednesday, bringing wind gusts up to at least 25-30 kt with a
30-50% chance for gale force wind gusts up to 35 kt. Confidence
in gale force wind gusts materializing is not high enough to issue
a Gale Watch at this time. Even if gale force wind gusts to 35 kt
do occur, it appears the coverage and duration for wind gusts of
this magnitude will be limited. Seas are forecast to peak around
10 ft on Wednesday, but could go higher if gale force wind gusts
do materialize. As such, there is currently a 1-5% chance seas
will peak as high as 13-15 ft. Seas are forecast to hold steady
near 10-12 ft on Thursday as well. -23

&&

.BEACH HAZARDS...An energetic westerly swell is expected along
the northwestern Oregon and southwestern Washington coasts through
Monday. A westerly swell with wave heights around 10-14 ft and a
predominant wave period between 14-16 seconds will result in a
high sneaker wave threat. These energetic waves can run
significantly farther up a beach than normal, including over rocks
and jetties, creating potentially life-threatening conditions in
the surf zone when beachgoers can be unexpectedly knocked off
their feet and pulled out into cold ocean waters.

A Beach Hazards Statement remains in effect through 10 AM Monday
to cover the high sneaker wave threat. Caution should be used
when in or near the water, and beachgoers with children should be
especially watchful. Never turn your back on the ocean, and be
sure to keep an eye on the waves. Those participating in razor
clam digs should also exercise caution. -23

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 10 AM PST Monday for PZZ210-251>253-
     271>273.
&&

$$

www.weather.gov/portland

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