490
FXUS66 KPQR 181113
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
400 AM PDT Sat Oct 18 2025

.SYNOPSIS...A robust frontal system arrives late Saturday into
Sunday, bringing widespread soaking rain to the area with gusty
southerly winds. Trending drier Sunday night into early next
week, aside from the south WA/north OR coast where light rain appears
increasingly likely Monday night into Tuesday morning. A stronger
weather system is possible late next week, bringing heavier rain and
the potential for impactful wind gusts. However, uncertainty remains
high for exact wind gusts and rain amounts.

&&

.SHORT TERM...Now through Sunday Night...Not much change to the short
term forecast with today`s update. The forecast is generally on track
as high pressure remains in place Saturday morning, bringing mostly
clear skies and light winds aside from some patchy fog and low clouds
in the Cascade and Coast Range valleys. As expected, the coldest
areas this morning are generally over the Upper Hood River Valley,
south WA Cascade foothills, and Battle Ground area where temps have
dipped into the 30s. Frost or freeze headlines remain in effect for
these areas through 9 AM Saturday. Elsewhere, temperatures are
generally in the low to mid 40s.

Despite the chilly temperatures in place Saturday morning,
temperatures will rebound nicely in the afternoon with highs in the
60s, except near 70 degrees in Eugene-Springfield, Creswell, Blue
River, Lowell and Oakridge. These areas will see sunny skies
throughout the day aside from patchy morning fog, however northern
areas will see clouds begin to increase ahead of the next frontal
system. Models remain in good agreement on the timing of this front,
bringing stratiform rain to southwest Washington and the north Oregon
coast Saturday evening and then the rest of northwest Oregon from
Lane County northward Saturday night into Sunday morning.

Persistent stratiform rain will transition to post-frontal showers by
mid Sunday morning. This is when forecast soundings show 850 mb
temperatures cooling to +1 to +2 degrees Celsius, with SBCAPE values
increasing to 100-200 J/kg and equilibrium levels generally below -10
degrees Celsius. However, 0-3 km AGL bulk shear values are fairly
high at 30-35 kt (have opted to use 0-3 km AGL bulk shear values
instead of 0-6 km as cloud tops generally look to stay near or below
3 km). Both speed shear and directional shear are in place, as the
wind direction will veer with height for a few hours or so as the
upper level trough axis moves overhead late Sunday morning/early
afternoon. The limited instability and shallow nature of Sunday`s
convection suggests overall lightning activity will most likely be
limited (which helps explain why NBM thunder probabilities only peak
around 15-25%). However, whether lightning occurs or not, stronger
showers will have the potential to produce a funnel cloud, landspout,
or gusty outflow winds up to 45 mph given the environmental wind
profile in place, meaning highly localized wind damage is possible.
Note southerly winds will be breezy in general Saturday night and
Sunday, even away from showers and thunderstorms. Currently expecting
southerly wind gusts up to 25-30 mph for inland areas and up to 30-40
mph for the south WA/north OR coast. Gusts up to 40-50 mph appear
likely in the high Cascades. Now would be a good time to secure any
loose outdoor objects you may have. Winds will weaken Sunday night
while any lingering showers begin to dissipate. -23/03

&&

.LONG TERM...Monday through next Saturday...Most model guidance
suggests mainly dry weather with seasonable temperatures, relatively
light winds and a mix of clouds and sun Monday and Tuesday. The main
exception to that will be the south WA/north OR coast where there is
a 30-50% chance of light rain. The highest chance of rain is Monday
night and Tuesday morning. Inland areas have a 10-20% chance of light
rain Tuesday.

Chances for more substantial rain gradually increase late Wednesday
through Friday, peaking near 80-90% by early Friday morning. This is
when a moisture-rich frontal boundary with an axis of heavier rain
will take aim at western WA/OR, bringing widespread rain and gusty
southerly winds to the region. Although confidence is high conditions
will trend much wetter and breezier Friday into next Saturday,
confidence remains low for exact wind speeds, rain amounts, and
associated impacts. Given the relatively low river levels heading
into this system, river flooding is not expected despite river rises
and forecast uncertainty on rain amounts. What appears to be more
concerning is the potential for damaging wind gusts late Friday into
next Saturday, but only if a deep surface low winds up tracking
towards the coast like some ensemble members from the ENS show.
Ensemble low locations vary significantly both spatially and
temporally, with some ensemble guidance suggesting
a fairly weak low with minimal impacts, while other members
suggest a very strong low capable of wind damage somewhere along
the Washington, Oregon, or northern California coast. That said, the
ENS has begun showing more ensemble clustering for a strong low with
a central pressure somewhere between 960-980 mb moving near Astoria.
This scenario would result in impactful wind damage. On the contrary,
there are still a relatively larger number of ensemble members that
show either a weaker low and/or a different low position that remains
further offshore. In addition, the GEFS also suggests a weaker low
with a central pressure around 990-1000 mb, with only one or two
members pushing a stronger low inland. In other words, we have a low
probability for a moderate to high impact wind event that bears
watching over the coming days. There is currently a 15-30% chance for
max wind gusts of 45 mph or stronger across all of northwest Oregon
and southwest Washington, except for a 40-60% chance at the coast and
on exposed ridges in the Coast Range and Cascades. Probabilities for
max wind gusts over 55 mph range between 5-15%, except 20-30% at the
coast and over higher terrain. If wind speeds of this magnitude were
to occur, extensive tree damage and power outages would be expected,
especially given how many trees still have foliage on them. -23

&&

.AVIATION...Clear skies and light winds remain in place Saturday
morning in response to high pressure. Patchy fog and low clouds
have developed in portions of the Cascade foothills and Coast
Range valleys, but has generally stayed out of the Willamette
Valley. That said, guidance continues to suggest there is a
20-40% chance for LIFR to IFR vis/cigs to develop sometime
between 12-15z Saturday, with the highest chances in the central
and southern Willamette Valley. Areas of patchy fog and low clouds
should dissipate by 18-20z Saturday.

Attention then turns to Saturday evening/night. Cloud cover will
develop from northwest to southeast across the area after 00-03z
Sunday in response to an incoming frontal system. This system will
bring widespread MVFR cigs and rain to all terminals beginning
Saturday evening. Cannot rule out a brief period of IFR cigs at
the coast between 04-09z Sunday as the front pushes inland,
especially at KONP where chances for cigs below 1000 ft peak
around 65% during that time. Chances for IFR cigs for inland TAF
sites range between 10-20%. Gusty south to southwest winds will
also accompany the frontal passage, with gusts up 30 kt expected
at the coast. Winds will increase inland as well, with gusts up to
25-30 kt likely for all inland TAF sites between 06-12z Sunday.

KPDX AND APPROACHES...Clear skies and light winds will continue
through at least 12z Saturday. There is a 20-30% chance for a
brief period of LIFR to IFR vis/cigs to develop sometime between
12-15z Saturday, before dissipating by 18z Saturday. MVFR cigs and
rain will likely develop towards 06-08z Sunday as a front pushes
inland. Gusty southerly winds up to 25 kt will also accompany the
frontal passage. -23

&&

.MARINE...Seas have increased to 10-12 ft at 15-16 seconds as a
northwesterly swell arrives from a dying low pressure system over
the Gulf of Alaska. This will be hazardous to small craft, so
Small Craft Advisories remain in effect across all waters
including the Columbia River Bar Saturday night, before hazardous
seas up to 20 ft develop Sunday behind a frontal system.

The weather pattern remains active Saturday night into early next
week as a stronger frontal system progresses through the waters
and brings breezy southerly to westerly winds. Marine conditions
quickly amplify as a higher northwesterly swell enters the waters,
with seas peaking somewhere between 15 to 20 ft. Chances for seas
above 20 ft remain less than 10%, except over the northern outer
waters from 40 to 60 NM offshore where there is a 30-50% chance
for seas over 20 ft. In addition to increasing seas, winds will
likely gust up to 25-30 kt. Brief and isolated gale forced wind
gusts up to 35 kt are possible over the northern and central inner
waters (Cape Shoalwater to Cape Foulweather) including the
Columbia River Bar during the frontal passage Saturday evening into
Saturday night.

Seas will decrease later Monday into Tuesday morning, bottoming
out around 7-9 ft at 12-13 seconds before another potent
northwesterly swell arrives Tuesday afternoon and evening pushing
seas up to around 15 ft range again. An active weather pattern is
then expected to continue late Wednesday through Friday night with
a period of storm force wind gusts of 48 kt or stronger possible
(20-40%, except for a 50% chance over the northern inner waters,
including the Columbia River Bar). -23/10

&&

.BEACH HAZARDS...A northwest swell of 10-12 ft at 15-16 seconds
seconds has entered the coastal waters as expected. This increase
in wave energy will support a high threat for sneaker waves
through this weekend. A Beach Hazards Statement remains in effect
across the central and northern Oregon coast and the south
Washington coast through Sunday evening. Sneaker waves can run up
significantly farther on a beach than normal, including over
rocks, logs, and jetties. Sneaker waves can suddenly knock people
off of their feet and quickly pull them into the ocean which may
lead to serious injury or drowning. Caution should be used when in
or near the water. Always keep an eye on the waves, and be
especially watchful of children and pets. Remember, never turn
your back on the ocean! -10/23

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Frost Advisory until 9 AM PDT this morning for ORZ104.

     Freeze Warning until 9 AM PDT this morning for ORZ121.

WA...Frost Advisory until 9 AM PDT this morning for WAZ205-208.

PZ...Small Craft Advisory until 8 AM PDT Sunday for PZZ210-251>253-
     271>273.

     Hazardous Seas Warning from 8 AM Sunday to 5 AM PDT Monday for
     PZZ251>253-271>273.
&&

$$

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