664
FXUS66 KPQR 031803
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
1003 AM PST Mon Nov 3 2025

Updated aviation discussion.

.SYNOPSIS...A compact surface low will develop offshore before
moving through western Oregon later today. This will bring
light to moderate rain and increased southerly winds along the
central Oregon coast. Trending drier on Tuesday aside from a
few spotty light showers. The weather pattern becomes much more
active Tuesday night through Friday morning as a strong low
pressure system develops offshore and sends a series of fronts
into western WA/OR. Expect widespread rain and gusty winds with
each frontal passage, with the heaviest period of rain expected
Thursday and Thursday night. This is also when the strongest
winds are expected with max wind gusts likely peaking between at
least 30-40 mph inland and 50-55 mph at the coast. In addition,
coastal flooding is expected along portions of Highway 101 and
Fraser Road in Tillamook County around high tide on Wednesday
from 10 AM to 2 PM PST, with water up to one foot above ground
level.

&&

.SHORT TERM...Now through Tuesday...High clouds continue to
stream in along southwest flow ahead of a large trough that is
setting up over the northeast Pacific and PacNW. A shortwave
embedded within the larger scale pattern is set to approach WA
and OR, bringing another round of light to moderate rain to the
region today. Hi- res models show rain starting along the coast
by 6 am and inland between 5-8 am. A compact meso-low is also
expected to develop offshore and move northeast toward the
central Oregon coast late Monday afternoon and into the evening.
This will help support a period of more moderate rain. Overall,
expecting most locations to receive at least 0.5 inches of rain
with probabilities ranging from 50% in the southern Willamette
Valley and eastern Lane county and around 80% for the
Portland/Vancouver metro. Probabilities across the higher
terrain of the coast range and Cascades are greater than 80%
with totals likely closer to an inch or more through Monday
night.

Fortunately, hi-res model guidance suggest hourly rain rates will
stay under 0.20-0.25 in/hr, suggesting urban flooding will not be a
concern. There are no concerns for river flooding with this system
either. Lastly, a brief period of gusty south winds with peak wind
gusts up to 30-45 mph are likely along the central Oregon coast to
the south of Pacific City Monday evening as the mesolow moves inland.
The strongest wind gusts will occur along beaches and headlands.
Showers linger into Tuesday with a relative lull in precipitation
into the afternoon. The next front approaches the region Tuesday
evening with the return of light to moderate rain. -19/23

.LONG TERM...Tuesday night through Saturday night...Models continue
to show good agreement in the large-scale synoptic pattern that sets
up by mid-week with a broad upper level trough over the northeast
Pacific and PacNW. The smaller scale features such as surface low
location and intensity along with embedded shortwaves vary among the
models and their ensemble members. Overall, the pattern is expected
to be wet and windy with gusts 25- 35 mph inland and 35-45 mph along
the coast.

Digging into the details for the week, models continue to show
good agreement in two distinct surges of moisture associated
with two strong fronts moving through the PacNW. The first wave
arrives Tuesday night into Wednesday with increasing southerly
flow and a slug of moisture. Integrated Vapor Transport (IVT) is
expected to be decent with this system, leading to a moderate
atmospheric river lasting 24-36 hours. IVT peaks just shy of 750
kg/ms but stays above 250 kg/ms for over 24 hours. This indicates
the system will be associated with plenty of moisture, leading
to a good soaking rain for the region. Expect 0.75-1.25 inches
for inland valleys and 1.0- 2.0 inches in the Coast Range and
Cascades. Winds will also increase on Wednesday with gusts 30-40
mph inland and 45-50 mph along the coast. This would be strong
enough to result in some tree damage and power outages, but would
not be strong enough for widespread downed trees and significant
impacts. There is still a 5-20% chance wind gusts reach 45 mph
or greater inland and a 20-40% chance for wind gusts of 55 mph
or greater for beaches and headlands based on NBM guidance. If
guidance trends towards these higher gusts materializing,
headlines would be issued for downed trees and power outages.
For now, conditions just look wet and windy with impacts
remaining minimal.

Conditions remain showery Wednesday night into Thursday the
region sits between impactful systems. The next system is
expected to move into the region late Thursday, bringing another
round of rain and gusty winds. Wind speeds with this front look
to be fairly similar to Wednesday, except at the coast and
higher elevations in the Coast Range where probabilities for max
wind gusts over 55 mph are relatively higher (35-60%
chance).This frontal system is also on track to produce the
heaviest rain of any of the frontal systems impacting the area
this week. WPC QPF amounts from 4am Thursday through 4am Friday
range between 1-1.25 inches for inland valleys, 1.5-2.0 inches
for the coast and Cascade foothills, and 2-3 inches for the
Coast Range and south WA/north OR Cascades. Given all the rain
that is forecast to fall prior to the system on Thursday, rising
river levels will be a concern. The main question that remains
is whether or not enough rain will fall for some rivers to reach
flood stage on Wednesday and/or Thursday. According to the
latest HEFS guidance, the probability for any given river to
reach minor flood stage is generally 10% or less, except a 25%
chance for the Wilson River near Tillamook. Another river of
concern would be the Grays River near Rosburg. Small creeks and
streams are more likely to see some minor flooding. Lastly,
minor urban flooding will also be possible, especially in low-
lying areas with poor drainage. Rain chances remain in the
forecast Friday through Saturday night, however ensemble
guidance suggests rain amounts will be lighter and less
impactful. Winds will also be weaker by then. -19/23


&&

.AVIATION...Widespread rain continues across the region through
around 05-07z Tue with scattered showers continuing through around
12z Tue. VFR conditions expected to trend toward widespread MVFR
ceilings after 19-21z Mon as a heavier band of precipitation moves
into the region. Moderate to heavy rain at times may also bring VIS
down to 4SM-5SM from 20z Mon to 03z Tue. Winds generally south to
southeast less than 10 kts. Then a compact surface low is expected
to track toward the central Oregon coast tonight, bringing increased
southerly winds to KONP and KEUG between 03-10z Tue. Wind gusts up
to 20-25 kt are possible.

KPDX AND APPROACHES...Rain continues through around 08-10z Tue.
Expecting MVFR ceilings after ~21z Mon as a heavier round of rain
moves through the region with flight levels around 25-30kft. Vis
could temporarily fall to 3-5SM in heavier rain. After the
widespread rain ends around 08-10z Tue, expect stratus to lower to
around 12-15kft for a few hours. Winds mainly from the southeast
less than 10 kts, temporarily becoming southerly at some point
between 04-12z Tue as a compact surface low moves over the region.
-03

&&

.MARINE...Easterly winds are expected to relax and turn southerly
as the offshore pressure gradient weakens and low pressure
approaches from the southwest. Seas remain steep with heights in
the low teens and a period of 13 to 15 seconds. A Small Craft
Advisory remains in effect for all zones through 4 pm. A compact
mesolow is set to develop and track toward the central Oregon
coast, bringing localized gusty winds. Guidance suggests winds
will increase for the outer and inner southern waters (PZZ273-253)
along with the central inner waters (PZZ252). Have opted to just
extend the Small Craft Advisory for these three zones for
southerly winds 15 to 20 kt and gusts to around 30 kt until 4 am
Tuesday. Isolated wind gusts to 35-40 kt possible but not expected
to be persistent.

An active pattern for all waters will return by mid week as
several strong systems are set to bring Gale and possibly Storm
force conditions. NBM 24 hour probabilities for winds to reach
Gale criteria increase to 70-90% for the outer waters late
Tuesday, spreading to all waters Wednesday and Thursday. The
probability of Storm force winds during the same time period
start out at 20-50% for the outer waters late Tuesday and spreads
to all waters Wednesday and Thursday. It should be noted that the
40-50% probabilities are more widespread on Thursday compared to
Wednesday. Seas are also expected to increase, with mainly wind
driven seas pushing into the mid to upper teens by Wednesday and
lasting into Thursday. Guidance currently suggests a 5-10% chance
that seas will exceed 20 ft. There is still plenty of uncertainty
in exact details but the active pattern is expected to persist.
-19/12

&&

.BEACH HAZARDS...A westerly swell of 11-14 ft at 14-15 seconds
will bring a high threat of sneaker waves today along the North
and Central Oregon Coast, and the South Washington Coast. 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. Those
participating in razor clam digs should exercise caution.

Additionally, there is a Coastal Flood Advisory for minor tidal
overflow flooding during high tide from 10 AM to 2 PM Wednesday
for the South Washington Coast, Clatsop County Coast, and
Tillamook County Coast. Minor flooding, up to 1 foot above ground
level, during high tides is expected in the low lying areas near
bays, sloughs, and the lower reaches of the coastal rivers. Expect
flooding along portions of Highway 101, including near Raymond,
Seaside, and Fraser Road in Tillamook County. Coastal residents
in the warned area should be alert for rising water, and take
appropriate action to protect life and property. Remain out of
the water to avoid hazardous swimming conditions.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Coastal Flood Advisory from 10 AM to 2 PM PST Wednesday for
     ORZ101-102.

WA...Coastal Flood Advisory from 10 AM to 2 PM PST Wednesday for
     WAZ201.

PZ...Small Craft Advisory until 4 PM PST this afternoon for PZZ210-
     251-271-272.

     Small Craft Advisory until 4 AM PST Tuesday for PZZ252-253-273.
&&

$$

www.weather.gov/portland

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