282
FXUS66 KPQR 241805 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1005 AM PST Mon Nov 24 2025

Updated aviation and marine discussions. Updated PQR
WATCHES/WARNINGS/ADVISORIES.

.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...A mixed bag of flight conditions is occurring this
morning, with mainly VFR conditions at the coast and mainly
IFR/MVFR conditions inland. There are also pockets of LIFR cigs
occurring, mainly impacting KHIO. Expect conditions to trend
towards MVFR to VFR this afternoon, before areas of fog and low
clouds redevelop over the Willamette Valley this evening into
tonight. Meanwhile, the coast should remain VFR due to the
development of offshore flow. KTTD will likely remain VFR for the
same reason. Fog/cigs will likely attempt lifting at least a bit
towards 12-16z Tuesday as widespread rain begins pushing into the
region from the west.

KPDX AND APPROACHES...Cigs will likely fluctuate between MVFR/VFR
this morning through 21z Monday before trending towards mainly VFR
thereafter. By 08z Tuesday, fog and low clouds will attempt
developing at the terminal before lifting towards 12-13z Tuesday as
rain begins to move in from the west. -23

&&

.MARINE...Seas have fallen to 7 to 9 ft as expected. Expect
westerly winds to continue weakening through today, before
becoming easterly for a brief period of time tonight. The next
frontal passage arrives late Tuesday into Wednesday, bringing a
shift to southerly winds with gusts up to at least 30 kt. There is
a 15-30% chance for gale force wind gusts up to 35 kt, except
around a 50% chance over the northern outer waters. 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.
Therefore, have decided not to issue a Gale Watch or Warning for
this frontal passage. Seas build to at least 10 to 13 ft with
this frontal passage with seas expected to peak on Thursday. There
is some uncertainty regarding how high seas will peak on Thursday. 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. -23/42

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...None.

&&

$$

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