159
FXUS66 KPQR 010534 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
934 PM PST Sun Nov 30 2025

Updated aviation discussion.

.SYNOPSIS...High pressure continues over the region today with
mostly dry conditions expected through Monday. Chilly
temperatures expected Monday morning. A weak front will bring
chances for light rain Monday night 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...Now through Tuesday Night...High pressure over the
area will keep today and Monday dry and generally clear with
cool overnight temperatures. While there have been a few
fluctuations in the forecast overnight lows, the overall impacts
will see little change. Continue to see high probabilities for
widespread frost in the lower elevations. Frost probabilities
are lowest within the Cascade valleys, the greater Portland-
Vancouver Metro, and exposed areas to higher winds. Elsewhere
(aside from the coast), there is greater than a 50% chance of
frost. In some rural areas it may be impactful enough to damage
any lingering vegetation. Those cooler temperatures will be
short lived though as a warm front moves over the area late
Monday into Tuesday. This front will bring rain to much of the
area but the main focus will be to the north and along the
terrain. 24 hour precipitation totals ending at 10 PM Tuesday
have lower end amounts of anywhere from 0.01-0.04" along the
coast with nearly nothing inland. higher end amounts though
range from 0.2-0.3" along the coast and up to 0.1" inland. In
southwest Washington though there is a 10% chance of 0.25" of
rain. Snow levels remain elevated so there is no risk for snow
in the lower elevations. -27


.LONG TERM...Wednesday through Sunday...Ensembles are consistent
in a high pressure ridge rebuilding on Wednesday. This ridge
will aid in pushing the front eastward and keep conditions
fairly "boring" through Thursday. Based on the global ensembles
there is around a 10% of some light continued precipitation
through the day on Wednesday but precipitation doesn`t start
ramping up until Thursday morning. This precipitation is
expected to be light through the day but picking up overnight.

On Friday there is a trend towards yet another warm frontal
system. This front is associated with a low pressure system over
the Alaska Panhandle. Stratiform rain will fall with the GFS
being the more robust system. With atmospheric warming this time
of year there is generally a concern for Atmospheric River (AR)
conditions. Based on the IVT values of both the GFS and ECMWF
there is a trend to a low to moderate AR that will persist
from the 4th through the 6th. When looking at the track,
vectors are pointing straight easterly which would bode well for
periods of heavy rain. Given the long duration, will have to
consider watching for any flooding impacts. The GFS continues to
be the most rain heavy scenario with around a 5% chance of
2-2.5" in 24 hours ending Saturday morning around Astoria, and
less than a 5% chance of greater than 1.25" around Salem.

Rain persists through Sunday. I will note that some models are
suggesting around a 10% chance of flooding after Sunday.
However, these values are likely being triggered by the GFS that
is running much higher than it`s other global ensemble
counterparts. -27

&&

.AVIATION...High pressure building offshore will maintain VFR
conditions through 06z Tuesday. Light and variable winds are
expected for all inland terminals through 06z Tuesday, except at
KTTD and KONP where east winds around 8-13 kt will continue
through approximately 18z Monday, strongest at KTTD. Not
expecting fog to develop tonight as the airmass in place is
relatively dry, favoring frost development instead of fog as
temperatures dip into the low to mid 30s.

Towards 05-06z Tuesday, probabilities for MVFR cigs around 3000 ft
increase to near 30% at KAST. Light rain showers are likely to
develop at KAST shortly after 06z Tuesday.

KPDX AND APPROACHES...VFR conditions expected through the period
with beneath scattered high clouds. Light and variable winds
around 5 kt or less are expected to continue through 06z Tuesday.
-23

&&

.MARINE...Benign weather continues across the coastal waters with
weak offshore flow at 5-10 kt and seas of 5-8 ft. Building high
pressure offshore will see flow turn increasingly out of the north
through Monday night while seas remain around 5 ft. A weak front
traversing the waters Monday night into Tuesday will see northwest
winds increase to 15-20 kt while a long-period westerly swell will
build seas to 9-11 ft on Tuesday. Winds and seas then ease midweek
before a more active weather pattern develops late in the week. At
this point, there are 25-40% chances seas rise above 10 ft again
Friday into next weekend, but this potential hinges on the track
and intensity of any potential weather system. -36

&&

.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...None.

&&

$$

www.weather.gov/portland

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