059
FXUS66 KPQR 011043
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
243 AM PST Mon Dec 1 2025

.SYNOPSIS...High pressure continues over the region today with
mostly dry conditions expected through this evening. A weak front
will bring chances for light rain tonight into Tuesday. Dry again on
Wednesday. Active weather returns as a series of frontal systems
bring increasing chances for rain later Thursday through the
weekend. Seasonable temperatures continue through the week.

&&

.SHORT TERM...Today through Wednesday night...An upper ridge of high
pressure over the region this morning will shift east as a shortwave
trough drops down across the Pacific NW tonight. After a chilly and
frosty start across much of the area today, expect increasing clouds
with afternoon temperatures only warming into the upper 40s through
much of the lowland valleys. Temperatures likely a bit warmer along
the coast thanks to some light offshore flow.

A weak frontal system will push across the area later tonight into
Tuesday. Rainfall accumulations are expected to be minimal as
showers remain relatively shallow as a warmer air mass persists in
the mid-levels. Most locations will only see a few hundredths of an
inch of rain, except along the north coast, and in the higher
terrain influenced by orographic lift, where amounts will vary up to
a quarter inch. There is less than a 10% chance in these areas for
amounts up to a half inch of rainfall.

High pressure rebuilds across the region on Wednesday with dry
weather and seasonable temperatures expected. Increasing moisture in
the mid levels within the north to northwest flow aloft will likely
maintain some sort of cloudiness. /DH

.LONG TERM...Thursday through Sunday...Models and their ensembles
are in good agreement that the upper level ridge remains over the
northeast Pacific on Thursday. But, WPC cluster analysis does
indicate high probability of the ridge breaking down and flattening
out, allowing for more westerly flow into the Pacific NW Friday and
into the weekend. This should allow for frontal systems to bring
increased rainfall and more active weather to the area. Uncertainty
in rainfall amounts remains moderately high, but extreme rainfall
appears very unlikely. For example, the probability for IVT values >
250 kg/m/s from the coast to the foothills is quite high (greater
than 80-90%) both Friday and Saturday, but the probability of IVT
values greater than 500 kg/m/s is very low. Both the GEFS and ECMWF
ensemble means suggest total precipitation amounts of around 2
inches near Astoria through Sunday. The NBM suggests similar amounts
for Friday through Sunday (72-hour period), while the 90th
percentile (10% chance of exceeding) suggests potential for total
rainfall amounts nearing 3 to 4 inches. Still, more beneficial with
minimal impacts expected. Will note that HEFS guidance does show
increasing (but still low) chances for local rivers reaching action
or minor flood stage, with the highest chances for coastal rivers
(up to 5-15%) into early next week. /DH

&&

.AVIATION...An upper level ridge of high pressure will maintain
predominately VFR conditions through at least 06z Tuesday. An
exception to this is patchy stratus across parts of the southern
Willamette Valley, as well as along the lower Columbia River near
KKLS. MVFR CIGs are likely to linger near KEUG through 14-16z this
morning, while LIFR CIGs should stay north of the Portland metro.
Light and variable winds along with mostly clear skies this
morning will allow for cooler temperatures into the lower 30s,
which favors frost development.

By 06z Tuesday, probabilities for MVFR cigs around 3000 ft
increase to near 50% at KAST as a weak front approaches the area.
Light rain showers are likely to develop at KAST shortly after
06z Tuesday.

KPDX AND APPROACHES...VFR conditions expected through this
evening beneath scattered high clouds. There is less than a 10%
chance of IFR stratus approaching the terminal from the north
early this morning. Expect temperatures this morning to drop into
the lower 30s. Expect increasing clouds after 00z as a weak front
approaches from the northwest. Chances for MVFR CIGs increase
after 09z Tuesday. Light and variable winds expected today. /02

&&

.MARINE...With high pressure offshore today, will see north to
northeast winds to around 10 kt, while seas remain around 4 to 6
ft. A weak front traversing the waters tonight into Tuesday will
shift winds to northwest, increasing up to 15-20 kt, while a long
period westerly swell builds seas to around 9 to 10 ft on Tuesday.
Have issued a Small Craft Advisory for the outer coastal waters
north of Cape Foulweather to cover this marginal threat.

Winds and seas ease midweek as high pressure returns. A more
active weather pattern develops late in the week as a series of
frontal systems is expected to moves across the waters from
Thursday into the weekend. There remains a 20-40% chance of seas
rising above 10 ft again Friday into Saturday. /DH

&&

.BEACH HAZARDS...A long-period westerly swell is expected along
the northwestern Oregon and southwestern Washington coasts from
late Monday through Wednesday next week. Wave heights increasing
to 8 to 10 ft on Tuesday may not appear to present a safety risk
to those on area beaches, but these energetic waves will present a
moderate to high risk for sneaker waves, waves which can run
significantly farther up a beach than normal, including over rocks
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 has therefore been issued from 7 AM
Tuesday to 10 PM Wednesday. Sneaker waves can create potentially
life-threatening conditions in the surf zone when 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. -36

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 4 AM to 10 PM PST Tuesday for PZZ271-
     272.

&&

$$

www.weather.gov/portland

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