005
FXUS66 KPQR 171125
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
325 AM PST Mon Nov 17 2025

.SYNOPSIS...Light rain showers continue through Monday morning,
then a passing ridge will support drier conditions Tuesday and
Wednesday. The next impactful system arrives during the latter
half of the week, and while its evolution remains uncertain,
lowland rain and mountain snow are possible.

&&

.SHORT TERM...Now through Tuesday Night...Light rain showers
will continue to dwindle in coverage through the morning as the
responsible upper-level low sinks southward into California. A
cooler and drier air mass will move in on its heels as a brief
shortwave ridge traverses the region, bringing clearing skies
from west to east this evening into tonight. Despite the drying
trend, areas of fog are still likely to occur within sheltered
valleys in the Coast Range and around the periphery of the
Willamette Valley or other low spots through tonight.

Another weak shortwave will pass overhead Tuesday afternoon into
Tuesday night. For most, this feature will bring a brief return
to overcast skies, but some may see additional rain chances,
most likely along the coast from Tillamook County northward, as
well as much of southwestern Washington. Rainfall totals are
likely, a 60-80% chance, to remain under 0.1". Cooler air
moving in aloft will see snow levels fall from around 7000 ft
early this morning to 3000-4000 ft by Tuesday night, however the
low precipitation amounts mean very little in the way of
Cascade snow is expected from this quick-hitting system. Skies
trend clearer aside from areas of fog through Tuesday night.
Areas of frost are also possible in the coldest spots, including
the Hood River Valley, sheltered valleys in the northern Coast
Range, and portions of the southern Willamette Valley, as many
see their coldest night of the season so far with overnight
lows in the 30s. -36


.LONG TERM...Wednesday through Sunday...Dry conditions continue
into Wednesday afternoon before the next frontal system moves
onshore. Some uncertainty persists in the evolution of this
system, particularly whether the bottom of the approaching
trough again pinches off to form a closed upper low moving into
California, or if the trough remains more coherent as it tracks
over the Pacific Northwest. In the former case, much of the
region would be left with weaker forcing for precipitation and a
weaker push of cold air, leading to both lower lowland rainfall
and mountain snowfall. In the latter case, increased support for
precipitation along with colder air aloft could support more
impactful mountain snows, however the chances for significant
accumulations of 6 inches or more at pass level are 10% or less.
Chances for even light accumulations of one inch at pass level
are only 45-55% at Santiam and Willamette Passes, and 10-15%
along US-26 near Government Camp. Otherwise, near to slightly
above normal temperatures in the low to mid 50s and overnight
lows in the upper 30s to mid 40s. -36

&&

.AVIATION...Largely MVFR flying conditions continue as light rain
showers linger behind an earlier frontal passage. Cigs at 2-4 kft
and vis of 5-7 SM will likely (60-80% chance) continue through
15-18z Mon as skies trend clearer and cigs lift above 4 kft.
Showers will dwindle in coverage through the afternoon, ending by
21-24z Mon without further impacts to area terminals. North to
northwest winds at 5-10 kt continue across the region with gusts
to 15 kt along the coast, easing to 5 kt or less after sunset.
There are low probabilities of fog late in the period, most likely
at KEUG after 09z Tue.

KPDX AND APPROACHES...MVFR conditions expected to trend to VFR by
15-16z Mon as cigs lift to 4 kft. Light rain showers linger
through the morning with limited terminal impacts, then dissipate
after 21z Mon. Northwest winds at around 5 kt ease to 3 kt or
less after sunset. -36

&&

.MARINE...North-northwesterly winds with gusts up 25 knots persist
across the waters behind the recent frontal passage while seas
have built to 10-14 ft at 12-13 seconds. Winds and seas alike will
continue through this afternoon before easing below 10 kt and 10
ft, respectively this evening. Small Craft Advisories therefore
remain in effect through 7 PM PST for the Columbia River Bar, and
through 10 PM PST elsewhere.

A brief reprieve from the active weather is expected Tuesday and
Wednesday as seas subside to 5-8 ft at 11-12 seconds. Winds will
similarly ease while remaining out of the northwest through
Tuesday night. Late Wednesday through the weekend, a more active
pattern returns as another frontal system moves into the region
increasing wind gusts to 20-30 kt. A building westerly swell will
see a 60-75% chance of seas reaching 15 ft or higher beyond 20 NM,
and lesser chances nearer to the coast. There is roughly a 10%
chances seas reach 20 ft beyond 20 NM. Seas are expected to peak
Thursday evening or early Friday morning, then will be slow to
subside, remaining above 10 ft into the weekend. -36/42

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 7 PM PST this evening for PZZ210.
     Small Craft Advisory until 10 PM PST this evening for
     PZZ251>253-271>273.

&&

$$

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