351
FXUS66 KPQR 241017
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
217 AM PST Mon Nov 24 2025

.SYNOPSIS...Shower activity continues to decrease today, but
cannot rule out some isolated, lingering showers through the
afternoon. A shortwave ridge builds over the area through
Tuesday afternoon. Then, the first in a series of systems
arrives by Tuesday, bringing widespread rain. Wet and cool
weather continues through the middle of the week and into
weekend. There is the potential for much colder temperatures for
the latter part of this week and through the weekend.

&&

.SHORT TERM...Today through Wednesday Night...Shower activity
continues to gradually decreases this morning as the front,
which brought the precipitation yesterday continues to exit the
region. Winds become west/northwest behind the front, but
generally remain light. The breeziest areas will be the high
Cascades and eastern Columbia River Gorge where westerly winds
could gust up to 30 mph. Temperatures will also cool down
behind this system, making for a chillier Monday and Tuesday as
850 mb temperatures drop towards -4 to -6 C, as a result, snow
levels drop below pass-level (2500-3500 ft). A very weak front
will maintain a 20-40% chance for lingering showers through
Monday afternoon, but drier conditions return by Monday night
as a shortwave ridge builds over the Pacific Northwest ahead of
a series of back-to-back systems. Monday night into Tuesday
morning is shaping up to be the will be the chilliest time of
the week, with overnight lows forecasted to drop into the low
to mid 30s across interior lowland valleys. Moist surface
conditions and light winds will result in the potential for
frost/fog development early Tuesday morning, especially over
grasses and elevated metal surfaces in outlying, rural areas.
One factor that could inhibit frost/fog development is cloud
cover. Model soundings show that there will mainly be high
clouds, so if these high clouds end up being too thick, then
radiational cooling may not be as efficient for frost/fog
formation.

By Tuesday afternoon, a shortwave, upper level ridge will be the
harbinger of a warming trend. However, do not expect a reprieve
from precipitation as slug of warm, moist air will bring
widespread precipitation back into the forecast by Tuesday
afternoon. Since this would be a warmer system with 850 mb
temperatures around 2 to 4 C, snow levels will climb above 6000
ft and result in rain over the Cascade passes. Conditions
remain showery through Wednesday night as this system moves
through the region. 48 hour liquid precipitation exceeding 1"
from 4 AM Tue to 4 AM Thu are around 45-90% along the coast,
Coast Range, Willapa Hills, and Cascades (highest chances
further north, lowest toward Lane County), 15-40% across the
Willamette Valley and Upper Hood River Valley, and 45-70% across
the southwest WA lowlands. /42

.LONG TERM...Thursday through Sunday...Wet weather is expected
to continue through the latter part of the week and into the
weekend as a system move into the region. While the current
deterministic track of this system has it taking aim at
Vancouver Island, before stalling briefly, then diving southward
on Saturday. There is a lot of uncertainty with the exact track
and magnitude of the system, which means that precipitation
totals as well as temperatures for the holiday are resulting in
a challenging forecast. However, 48 hour liquid precipitation
exceeding 0.50" from 4 AM Thu to 4 AM Sat are around 40-60%
along the the coast, Coast Range, Willapa Hills, and Cascades
and 20-50% across interior, lowland valleys.

Given the high uncertainty with the aforementioned system, the
majority (50-70%) of ensembles are showing cooler air coming
into the region Saturday into Sunday. The 00Z run of the GFS has
850 mb temperatures of -2 to -7 C, while the same run of the
ECWMF has 850 mb temperatures of 1 to 5 C. So, with this vast of
a temperature spread, you may notice towards the end of the
forecast period (Saturday night into Sunday) that there is a
mention of a rain/snow mix all the way down to the Willamette
Valley floor and southwest WA lowlands. While a rain/snow mix
is possible, the probabilities for this outcome to occur are
currently very low (1-5%). To summarize, overall model spread
is very large for both temperatures and precipitation amounts.
This means forecast confidence is very low. However, we will
remain vigilant over the next few days and will update the
forecast as needed. /42

&&

.AVIATION...What remains of a weak frontal passage will continue
to push eastward out of the local air space. This is resulting in
northwesterly flow aloft and with flight conditions generally
improving towards predominately VFR with isolated pockets of
MVFR. Another weak front may bring some very light showers to
northern portions of the area through around 00Z Tuesday, with
little to no impact to overall flight conditions expected. A
shortwave ridge will build over the region after 00Z Tuesday and
will bring about a 15-30% chance for IFR/LIFR conditions
developing along the I-5 corridor starting around 06Z Tuesday and
persist through at least the remainder of the TAF period.

KPDX AND APPROACHES...Predominately VFR conditions expected
through the majority of the TAF period. A weak front may bring
some very light showers to northern portions of the area through
around 00Z Tuesday. Around 06Z Tuesday, there is a 15-30% chance
for IFR/LIFR conditions developing at or near the terminal through
at least the end of the TAF period. /42

&&

.MARINE...Seas will remain around 9 to 12 ft before falling to 7
to 9 ft by Monday afternoon and then 6 to 8 ft on Tuesday. The
next frontal passage arrives Tuesday night into Wednesday,
bringing wind gusts up to 30 kt with a 15-30% chance for gale
force wind gusts up to 35 kt. Confidence remains low, so will
refrain from issuing a Gale Watch at this time. Even if gale
force wind gusts to 35 kt do occur, it appears the coverage and
duration for wind gusts of this magnitude will be limited. Seas
build towards 10 to 13 ft with this frontal passage with seas
expected to peak on Thursday. There is some uncertainty as to the
exact path of this system. As such, there is currently a 10%
chance seas will peak around 16-19 ft, with a 1-5% chance for seas
will reach 20 ft or higher Thursday into Friday. /42

&&

.BEACH HAZARDS...An energetic westerly swell is expected along
the northwestern Oregon and southwestern Washington coasts through
Monday. A westerly swell with wave heights around 10-14 ft and a
predominant wave period between 14-16 seconds will result in a
high sneaker wave threat. These energetic waves can run
significantly farther up a beach than normal, including over rocks
and jetties, creating potentially life-threatening conditions in
the surf zone when beachgoers can be unexpectedly knocked off
their feet and pulled out into cold ocean waters.

A Beach Hazards Statement remains in effect through 10 AM Monday
to cover the high sneaker wave threat. Caution should be used
when in or near the water, and beachgoers with children should be
especially watchful. Never turn your back on the ocean, and be
sure to keep an eye on the waves. /42

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 10 AM PST this morning for PZZ210-
     251>253-271>273.

&&

$$

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