796
FXUS66 KPQR 031037
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
237 AM PST Wed Dec 3 2025

.SYNOPSIS...High pressure nudges into the region with dry
conditions expected today, along with widespread fog through this
morning. A series of fronts will bring a period of wet weather
Thursday through the weekend across southwest Washington and
northwest Oregon with potentially more impactful rain next week.

&&

.DISCUSSION...Today through Tuesday...Fog and low stratus this
morning will give way to high clouds and dry weather this afternoon.
Water vapor satellite imagery depicts an upper level ridge over the
northeast Pacific with mid to upper level moisture persistent within
the northerly jet stream over the region. Expect a pattern change
beginning Thursday as the upper ridge eventually flattens out and
allows for zonal flow across the area. A series of upper level
shortwaves and associated frontal systems will move across the
northern Pacific into the Pacific Northwest through the weekend and
into early next week.

The initial warm front arrives Thursday morning bringing light rain
across mainly northern portions of the forecast area. Rain steadily
increases through the afternoon, but much of the southern and
central Willamette Valley will likely remain rain shadowed through
Thursday evening. Rainfall is expected to intensify through Friday
afternoon as the mid-level flow turns more westerly and IVT values
peak around 500-600 kg/m/s. Rainfall totals through Friday night are
expected to be highest in the Coast Range and the northern Oregon to
south Washington Cascades. Latest 48-hr QPF indicates mean values of
around 2-3 inches of rainfall in the higher terrain of the Coast
Range and Cascade foothills, while the 90th percentile values are
closer to 3.5-4.5 inches.

Onshore flow continues through the weekend with periods of rainfall
Saturday and Sunday as various shortwaves move through. There still
remains a bit of uncertainty within the ensemble suites. But
overall, widespread flooding impacts are not expected with these
rounds of precipitation.

Uncertainty continues into early next week, but there is a trend
among the ensembles that indicates a potential for heavier rainfall
associated with a possible moderate to strong atmospheric river late
Monday into Tuesday. However, there is significant spread in the
members between where the strongest band of moisture will funnel
between WA and OR along with the maximum strength of the IVT values.
One thing to note is soils will already be saturated and river
levels elevated from the days of rain leading up to this event.
Depending on the strength of this this event, flooding could be a
concern. HEFS guidance for many rivers indicates a 10-25% chance of
certain rivers reaching action stage and a 5-20% chance for minor
flood stage, mainly focused on the Dec 9-10 time period.
Additionally, there are signals for breezy winds with the frontal
system associated with this event, although the spread is also very
wide. If winds do end up even around 30-40 mph, saturated soils
could cause some localized impacts due to downed trees. Keep in mind
there`s still the potential that this event could be more similar to
the lower impact event of this weekend.

&&

.AVIATION...As of 09z Wednesday, satellite imagery reveals a break
in the high clouds with widespread low stratus across the area;
while surface observations show LIFR fog developing at inland
terminals. An upper ridge of high pressure over the NE Pacific
will gradually shift eastward maintaining northwesterly flow
aloft. IFR to LIFR conditions are likely, 50-80% chances, at
inland terminals. Vis favored to improve back to MVFR/VFR by
15-18z Wed, then cigs improve as low stratus breaks up by 18-22z
Wed. Most guidance tends to clear these conditions too early this
time of year, and while corrections have been attempted to account
for this timing bias, there are 10-30% chances that MVFR cigs in
particular linger past 21-22z Wed, most likely in the southern
Willamette Valley including at KEUG. Calm to light and variable
winds are expected inland, building to 2-5 kt out of the north to
northwest Wednesday afternoon. Along the coast, light offshore
flow will limit chances for widespread fog, however favored east-
southeasterly flow at KAST could still see periods of MVFR vis
within mist overnight. Otherwise, largely VFR conditions with
easterly winds turning northerly to northeasterly Wednesday
afternoon.

KPDX AND APPROACHES...Fog and low stratus expected to deteriorate
conditions through 18z Wed. Chances for 1/2SM or less vis are
50-60% through much of the overnight period, before vis
restrictions improve by 16-17z Wed. Low stratus may linger later
into the morning, but is expected to break up by Wednesday
afternoon. Calm to light and variable winds overnight will
increase out of the northwest to 3-5 kt.

&&

.MARINE...High pressure over the waters today will maintain
northerly winds 10 kt or less through tonight. Seas around 6 to 8
ft continue to subside as well.

Active weather returns as winds turn southerly on Thursday ahead
of the first in a series of fronts. There is a 70-90% chance for
wind gusts to reach 22 kt across the northern coastal waters, but
still some uncertainty with the duration of the strongest winds.
Winds turn onshore behind the frontal passage with southwest winds
again increasing on Friday as another, slightly stronger front
moves across the waters. Expect this parade of fronts to continue
through the weekend, and into early next week. There is a 50-60%
chance for gale force wind gusts on Monday.

Seas are expected to remain below 10 feet through at least Friday.
There is a 30-40% chance of seas exceeding 10 feet by Saturday
morning.

&&

.BEACH HAZARDS...A long-period westerly swell is expected to
continue along the northwestern Oregon and southwestern
Washington coasts through Wednesday. Waves may run up farther
than normal on beaches, including over rocks, logs, and jetties.
In addition, a period of perigean spring or "king" tides means
these waves will have an even easier time reaching high up onto
beaches, limiting the areas which may be safe from wave action.
A Beach Hazards Statement therefore remains in effect through
10 PM Wednesday. Sneaker waves can create potentially life-
threatening conditions in the surf zone where beachgoers can be
unexpectedly knocked off their feet and pulled out into cold
ocean waters. Caution should be used when in or near the water,
and those 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
additionally exercise caution.

Additionally, there is a Coastal Flood Advisory for minor tidal
overflow flooding during high tide from 9 AM to 2 PM on Thursday
for the South Washington Coast and the Clatsop County Coast in
Oregon. Minor flooding up to 1 foot above ground level is
possible during high tide in low lying areas near bays, sloughs,
and the low reaches of the coastal rivers. Coastal residents in
the warned area should remain alert for rising water and take
appropriate action to protect life and property. Remain out of
the water to avoid hazardous swimming conditions. -19/36

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Coastal Flood Advisory from 9 AM to 2 PM PST Thursday for ORZ101.

WA...Coastal Flood Advisory from 9 AM to 2 PM PST Thursday for WAZ201.

PZ...Small Craft Advisory from 1 PM to 5 PM PST Wednesday for PZZ210.

&&

$$

www.weather.gov/portland

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