602
FXUS66 KPQR 011906
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
1100 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...Low clouds that developed overnight in the southern
Willamette Valley will slowly dissipate over the next few hours.
There is a 10-20% chance that IFR to MVFR restrictions either do not
retreat this afternoon or return quickly this evening to KEUG as low
stratus tries to redevelop ahead of the next front. Speaking of, a
weak front will drop southeastward across southwest Washington and
northwest Oregon overnight. Little in the way of wind will accompany
this front. This will result in a several hour window where ceilings
will have the potential to lower into IFR and MVFR thresholds as the
lower atmosphere saturates along the coast between 06-12z Tuesday
and between 12-18z Tuesday for inland taf sites. Our best
statistical model guidance suggests a 30-50% chance (highest for
KAST and lowest farther south towards KONP) for MVFR restrictions
developing at any given hour in the 06-12z Tuesday timeframe.
Probabilities are more in the 30-40% range for MVFR conditions to
develop at any given hour in the Willamette Valley, primarily in the
12-18z Tuesday timeframe. The highest chances for IFR conditions
will be at KAST in the 06-12z Tuesday timeframe and climb into the
20-30% range at KEUG and KHIO in the 12-18z Tuesday timeframe and
remain around 10% at other sites like KPDX and KSLE.

KPDX AND APPROACHES...VFR conditions will give way to lowering
ceilings as a weak front slides across the late terminal late
tonight into early Tuesday morning. Probabilities for MVFR ceilings
start climbing between 09-12z Tuesday as the front approaches the
region and then peak around 30-40% at any given hour between 12-18z
Tuesday as the front crosses the region. The probability of IFR
conditions developing at any given hour peaks around 10% between 15-
18z Tuesday.

&&

.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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