784
FXUS66 KPQR 290002 AAA
AFDPQR

Area Forecast Discussion...UPDATE
National Weather Service Portland OR
502 PM PDT Wed Oct 28 2026

Updated Aviation discussion

.SYNOPSIS...Cool and showery conditions continue through Friday
as an upper-level low sits offshore. Winter Weather Advisories
remain in effect across the Cascades through this evening. Clear
skies and calm winds may bring frost development across interior
valleys Saturday morning. Mostly dry conditions return this
Halloween weekend. Slight chances for precipitation return early
next week.

&&

.SHORT TERM...Today through Friday night...Radar imagery as of
late Wednesday morning depicts scattered showers across
northwest Oregon and southwest Washington as an upper-level low
spins off the coast of the Vancouver Island. For elevations
above 4500 feet, webcams and surface observations currently show
temperatures around 32F with some accumulating snow. Winter
Weather Advisories remain in effect for the north Oregon and
south Washington Cascades through 11 PM this afternoon, and
through 5 PM for the Marion, Linn, and Lane County Cascades.
High resolution guidance shows some moderate to locally heavy
snow showers continuing over the north Oregon and south
Washington Cascades through this evening, hence the later end
time for the advisory. Showers gradually taper off this evening
for the Cascades south of Clackamas County. Expect an additional
trace to 3 inches of snow for elevations above 4500 feet,
except 3 to 6 inches above 6000 feet. Despite advisory-level
snow amounts not being met, the advisory was issued to consider
any hikers or backpackers along the PCT or forest roads that may
still be open above the main passes.

Otherwise, expect a typically fall day west of the Cascades
with chances for showers continuing through this evening and
temperatures in the 50s for most locations. There is a slight
chance (15-20%) for thunderstorms this afternoon across interior
southwest Washington, the Portland-Vancouver Metro Area, and
Columbia River Gorge as we see some cloud breaks that allows for
some surface heating and increased instability. However,
chances for thunderstorms decrease once the sun starts going
down after 4-5 PM. Any passing thunderstorms may produce
lightning, heavy rain, gusty winds, and/or small hail.

Tonight into Thursday, the aforementioned upper trough moves
southward but remains offshore of the Pacific Northwest. This
will maintain chances for light showers across the area, with
the highest chances along the coast. Some locations along the
I-5 corridor, particularly from Salem southward, may remain
drier given that guidance isn`t showing this low moving inland.
Chances for 24 hour liquid precipitation exceeding 0.10 inch are
around 50-90% along the coast, 40-60% around the Portland-
Vancouver Metro Area to the Cowlitz Valley, and 10-25% from the
Salem southward and across the Cascades. Friday is a similar
trend but slightly drier as the upper low is kept offshore due
to upper-level ridging building over the Rockies and Central
U.S. Friday night into early Saturday morning, clearing skies
and calm winds will favor temperatures dropping into the low to
mid 30s across interior valleys, which may lead to fog or frost
development. Chances for Saturday morning lows dropping below 32
degrees is 60-90% across the southern Willamette Valley,
northern Clark County (Battle Ground area), and the Upper Hood
River Valley. -10

&&

.LONG TERM...Saturday through Tuesday...Heading into the
weekend/Halloween, the majority of ensemble members are showing
the offshore upper-level low moving into the Pacific Northwest.
It appears that there will be limited moisture with this low
coming in, so most ensembles show either dry conditions or light
precipitation amounts. However, there is still a low chance
(10-20%) for higher amounts of 0.10-0.20 inch between 5 AM
Saturday to 5 AM Sunday across  northwest Oregon and southwest
Washington. For those going out on Halloween, the weather is not
looking too impactful as we are not expecting heavy rain or
strong winds.

Sunday to Tuesday, the majority of ensemble members (75%) are
showing an upper-level ridging amplifying over the northeast
Pacific and shifting over the Pacific Northwest. If this pans
out, will see a trending trend across the region with a
temperatures increase of a few degrees. However, 25% of ensemble
members (mainly from the GFS and Canadian models) are showing
troughing moving into the Pacific Northwest by Monday-Tuesday.
If this pans out, then will maintain potential for cooler and
wetter weather. For now, chances for precipitation on Monday and
Tuesday are only around 10-25%.       -10


&&

.AVIATION...Through 00Z Friday...Westerly flow aloft shifts
southwesterly on Thursday as low pressure drifts over the NE
Pacific. Rain showers this evening are expected to decrease
overnight across inland terminals allowing for predominately VFR
conditions through 10-12z. Winds become light tonight with cloud
cover becoming scattered to broken. Probs for fog and reduced
surface visby below 1 SM are generally less than 10% tonight into
Thu morning, except around 20-30% near KEUG. Another round of
showers is likely between 10-18z Thu across northern portions of
the forecast area with around a 20-30% chance of MVFR.

KPDX AND APPROACHES...Occasional rain showers continue through 03z
this evening. Expect conditions to trend toward predominately VFR
tonight. Chances for rain showers increase again by 10-12z Thu,
with a mix of VFR/MVFR CIGs possible through 18z Thu morning.
Southwest winds around 6-8 kt are expected to become light
overnight, shifting to the southeast by Thu morning. /DH

&&

.MARINE...Buoy observations from early Wednesday morning showed
westerly winds around 10 to 20 kt with seas ranging between 7 and
10 ft at 8 to 10 seconds, with the highest winds and seas
occurring over the northern and central outer waters. Therefore,
these two marine zones have a Small Craft Advisory in effect
through 5 PM PDT Wednesday. Meanwhile, the inner waters and
southern waters have no headlines in effect as winds and seas have
fallen below small craft advisory criteria.

Winds and seas will slowly subside this evening into tonight in
the wake of a low pressure system. Seas decrease further Thursday
through the weekend. This will result in relatively benign
conditions across the coastal waters, with an exception within
the main channel of the Columbia River Bar where very strong ebb
currents Wednesday evening and Thursday evening will temporarily
push seas up. Seas on the bar are expected to peak near 10 ft with
west winds of 10 to 15 kt during the very strong ebb current
Wednesday evening. Seas should peak near 8 ft with south winds of
10 to 15 kt during the very strong ebb current Thursday evening.

Seas will build across the coastal waters on Monday in response
to the arrival of a long-period west-northwest swell with a
dominant wave period near 15-17 seconds. Significant wave heights
will most likely peak near 10 ft with the arrival of the long-
period swell, however there is a 20-40% chance wave heights will
peak over 10 ft. The highest probabilities for this to occur are
over the northern and central outer waters. Light offshore winds
are expected on Monday, suggesting seas will be primarily driven
by the long-period swell rather than wind waves. -23

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Winter Weather Advisory until 11 PM PDT this evening for ORZ126.

WA...Winter Weather Advisory until 11 PM PDT this evening for WAZ211.

PZ...Small Craft Advisory until 9 PM PDT this evening for PZZ210.

     Small Craft Advisory from 5 PM to 10 PM PDT Thursday for PZZ210.
&&

$$

www.weather.gov/portland

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