773
FXUS66 KPQR 092116
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
116 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...High SCT/BKN clouds continue to stream over NW Oregon
and SW Washington as a weak frontal system approaches the region
from the Pacific. East gusts up to 20-30 kts continue through the
western Columbia River Gorge into KTTD today, beginning to weaken
later this afternoon into the evening. Expecting gusts to fall
below 20 kts after 00-03z Mon. Ahead of the frontal passage
tonight, there`s a 10-30% chance of IFR/LIFR CIGs and VIS
developing for the central to southern Willamette Valley anywhere
between 03-10z Mon as long as high clouds remain on the thinner
side. If high clouds become more OVC, then fog/low stratus
development probabilities decrease even more. Confidence is too
low to include in TAFs at the moment, but will continue
evaluating.

Then as the frontal system approaches and moves through the region
late tonight/early tomorrow, CIGs begin to trend downward across
the entire region. There`s a 60-80% chance for IFR/MVFR CIGs
developing along the coast around 05-08z Mon and MVFR CIGs inland
around 12-16z Mon. Conditions are expected to remain lowered
through the TAF period, though inland locations could fluctuate
between MVFR and low-end VFR after 21z Mon. Light rain will also
accompany the front, ending by 00-03z Tue for most terminals.

KPDX AND APPROACHES...VFR conditions expected through tonight
with SCT/BKN high clouds. Ceilings expected to fall below 3-4kft
around 12-15z Mon as an approaching weak front brings chances of
light showers. Easterly winds around 10-12 kt through 00-03z Mon,
weakening to 2-5 kts after. -03

&&

.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...Small Craft Advisory from 4 PM this afternoon to 10 PM PST this
 evening for PZZ210.

&&

$$

www.weather.gov/portland

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