718
FXUS66 KPQR 100556
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
956 PM PST Sun Nov 9 2025

.SYNOPSIS...Dry weather will give way to a weak shortwave
trough, that will bring very light rain across the CWA tonight
into Monday. High pressure briefly returns on Tuesday, which
will bring about a short period of dry weather. A series of lows
will start to impact the region on Wednesday. These systems
will bring about widespread precipitation and colder air. Snow
levels expected to drop towards 4000 ft late Thursday/early
Friday, which will bring fresh snow to the Cascades for the
latter part of this week.

&&

.DISCUSSION...Tonight through Sunday...The upper level ridge,
which has been keep the CWA dry this weekend as well as easterly
winds through the Columbia River Gorge will slowly flatten as a
weak, shortwave trough moves across the Pac NW late tonight
through Monday. High pressure briefly returns on Tuesday which
will bring warm and dry conditions. However, a significant
pattern change is on the horizon as a series of systems are
expected to bring widespread precipitation, onshore flow and
cooler temperatures through next Sunday.

Tonight, easterly winds will continue to slowly subside through
the overnight hours. Current observations have easterly gusts
at KTTD (Troutdale) around 30-35 mph with gusts of 40-50 mph at
exposed ridgetops within the Columbia River Gorge (Three Corner
Rock, Crown Point/Vista House). As the ridge of high pressure
weakens, the pressure gradient from Portland International
Airport to The Dalles (KPDX- KDLS) will gradually ease towards
-3 to -5 mb tonight. As these pressure gradients ease, easterly
winds will also weaken through the Gorge and along the coast,
with more southerly winds expected late tonight.

Late tonight into Monday, a shortwave trough pushes into
southern British Columbia and far northwest Washington. High-res
ensemble guidance suggests that the front associated with this
upper level shortwave will be very weak as it quickly brushes
our CWA. This scenario is shaping up to be a mod/high PoP event
with low QPF. There is high confidence (70-80%) that 24-36 hour
rain amounts starting 8 PM Sunday will remain less than 0.10"
for most places. Currently, the highest chances for rain are
along the coast and southwest Washington (50-70%) as this weak
front is tracking further north, while chances for rain are
lower (15-30%) across interior northwest Oregon.

Tuesday, another shortwave upper level ridge builds over the
Pacific Northwest and will bring a brief return of dry weather.
However, by Wednesday, the first in a series of robust lows will
take aim at the Pac NW. This stronger system will bring rain
and cooler air back into the forecast. The first system will
bring widespread rain across the CWA Wednesday through Thursday
with the mean precipitation total across the CWA between
0.30-1.30" with higher totals along the coast, the 90th
percentile range from 0.80-2.50" and the 10th percentile range
from Trace to 0.30 inches.

As this first system pushes eastward, it will bring cooler
temperatures into the region. Models have 850 mb temperatures
dropping towards -1 to -3 C, which will result in snow levels
falling towards to pass-level in the Cascades Thursday evening/
Friday. Mean precipitation totals for low elevation, inland
locations from Friday afternoon through Saturday afternoon is
between 0.30-0.75" with higher totals along the coast, the 90th
percentile range from 0.70-2.00" and the 10th percentile range
from Trace to 0.15 inches. Current guidance also suggests a
40-60% chance that 48-hour snow totals between 10 PM Thursday to
10 PM Saturday exceeds 6 inches through the passes, with the
highest chances at the Santiam and Willamette Passes. As
Saturday approaches, warmer air will be introduced as the next
system moves into the region and this will result in continued,
widespread precipitation through the remainder of the weekend
and into Sunday. /42

&&

.AVIATION...Bkn/ovc high clouds continue to spread over NW Oregon
and SW Washington as a weak frontal system approaching over the
Pacific nears the coast this evening. Ahead of the boundary, east
winds at 15 kt gusting to 25 kt continue west of the Columbia
River Gorge at KTTD, however the east-west surface pressure
gradient has finally begun to weaken, allowing winds to east below
10 kt by 12z Mon. While light southeast winds reach to KPDX as of
0530z Mon, calm to light southerly winds are in place elsewhere
across the region. Ahead of the high cloud cover associated with
the front, areas of fog/mist or low stratus may develop in the
central/southern Willamette Valley as well as other sheltered
valleys nearby. KEUG maintains the best chances to see categorical
restrictions, with current MVFR vis expected to give way to
IFR/LIFR conditions by 08-10z Mon. Confidence in the occurrence of
fog/mist is lower at other Willamette Valley terminals (KSLE,
KCVO, KUAO), with MVFR vis/cigs more likely after 10-12z Mon.

As the frontal system arrives from the northwest and progresses to
the east/southeast across the region tonight into early Monday,
cigs will trend downward within rain showers, most likely along
the coast and from the northern Willamette Valley north into SW
Washington. Rain showers are expected to arrive at KAST by 08-11z
Mon, then inland to Portland-area terminals as well as southward
along the coast to KONP by 11-15z Mon. While coastal terminals
will have a 50-70% chance of bottoming out at LIFR cigs, inland
terminals are more likely (50-70% chance) to maintain MVFR cigs
during rain showers. While precipitation chances are lower to the
south at KSLE/KEUG, MVFR cigs remain favored through Monday
morning. Conditions look to trend upward behind the frontal
passage as winds turn out of the west/northwest at 5 kt or less.

KPDX AND APPROACHES...VFR conditions continue this evening ahead
of an approaching frontal system with light southeast winds at
KPDX, but gusty east winds persisting closer to the Columbia Gorge
at KTTD. Cigs are expected to trend down to MVFR during light
rain showers, most likely from 15-21z Mon, before improving to
VFR late in the period as winds shift out of the northwest. -36

&&

.MARINE...A weak frontal system approaching the waters Sunday
afternoon has shifted winds southerly. Winds generally expected
to remain below 15 kts with gusts below 20 kts as the front
passes through the waters tonight except for the outer waters
beyond 30 NM in zone PZZ271 where wind gusts could briefly reach
21-25 kts through 8 PM PST. Seas will generally remain 6-9 ft
at 10-12 seconds in Monday.

Wind direction varies through the first half of next week, but
wind speeds look to remain at 5-10 kt through Tuesday night.
There is also high confidence (greater than 95% chance) that seas
remain below 10 ft through midweek as well. An area of low
pressure strengthening well offshore will return breezy southerly
winds and building seas Wednesday into Thursday, increasing the
chances (60-80% chance) for another period of conditions hazardous
to small craft. There is also a 40-70% chance for Gale-force
wind gusts greater than 34 kt during this period, with the
highest chances across the outer waters beyond 20-30 NM. -10/36

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

www.weather.gov/portland

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