517
FXUS66 KPQR 010456 AAA
AFDPQR

Area Forecast Discussion...UPDATED National Weather Service Portland
OR 956 PM PDT Fri Oct 31 2025

...Updated aviation discussion...

.SYNOPSIS...
A cold front will bring rain to the region this evening into
Saturday, beginning along the northern Oregon and southern
Washington coasts before spreading inland overnight. Southerly winds
will increase this evening, with gusts generally between 20 and 25
mph across the lowlands. Drier weather follows on Sunday before
another round of active weather returns early next week.

&&

.SHORT TERM...Now through Saturday Night...
Mid and high clouds continue to thicken ahead of a frontal system
approaching from the northwest. Rain will begin along the north
Oregon and south Washington coasts between now (3 PM) and 5 PM,
spreading inland toward the Portland/Vancouver metro by early to mid-
evening (around 5 to 8 PM). Rain onset becomes more uncertain for
the central and southern Willamette Valley as the stalling front
pivots southeastward into the area. While rain is expected to begin
around 8 to 11 PM for Salem, it is possible that the frontal band
will weaken and stall, resulting in very light rain for Salem and
southward. Overall for this system, expect precipitation to start
light, then gradually increase in intensity through the night.

The approaching cold front will slow somewhat as it nears the coast
this evening, becoming vertically stacked before progressing
eastward overnight. An embedded shortwave will help accelerate the
front inland late tonight into Saturday morning. Rain will persist
through much of Saturday, gradually tapering to showers by the
afternoon/evening.

For rainfall totals from now through Saturday, expect around 0.75 to
2.50 inches along the coast and Coast Range, 0.50 to 1.25 inches for
the northern Willamette Valley, 0.25 to 0.75 inches for the southern
and central valley, and 0.5 to 3.0 inches across the Cascades and
foothills (locally higher on peaks). Heaviest totals are expected
for the Willapa Hills, North Oregon Coast Range, South Washington
Cascades and foothills due to the frontal orientation and timing.

Southerly winds will increase this evening with inland gusts in the
20 to 25 mph range and up to 25 to 35 mph for the coast, Coast
Range, and Cascades. Into Saturday morning and afternoon, expect
inland gusts around 20 to 30 mph and up to 30 to 40 mph for the
coast, Coast Range, and Cascades.

&&

.LONG TERM...Sunday through Thursday...Sunday will bring a break in
the active pattern as weak upper ridging develops and conditions dry
out. The respite will be short-lived, however, as rain may return as
early as Monday afternoon.

Model ensemble guidance shows good agreement through midweek,
indicating a broad trough settling over the Pacific Northwest by
Wednesday. This trough will be associated with an atmospheric river,
expected to persist around 4872 hours in duration. This atmospheric
river will be relatively weak through most of the duration. To note,
this atmospheric river will peak into moderate strength from Tuesday
evening to Wednesday evening, resulting in integrated vapor
transport around 500-700 kg/ms (therefore 24 hour duration as
moderate strength). With prevailing southwesterly flow expected with
this atmospheric river, orographic enhancement is expected to be
modest, limiting heavy rain potential. While this system bears
watching, current model guidance does not suggest rainfall rates
high enough to raise flooding concerns for rivers or urban areas.

Winds may increase again Wednesday into Thursday evenings, with a
1020% chance of gusts exceeding 45 mph, though probabilities can
change as ensembles come into closer agreement on the eventual track
and depth of the offshore low. Thursday and onward, ensemble spread
increases notably, suggesting growing uncertainty in timing and
strength of any subsequent systems. ~12

&&

.AVIATION...A frontal system pushing through the region will bring
a mix of MVFR/VFR CIGs and VIS across northwest Oregon tonight.
Periods of moderate to heavy rain may briefly bring CIGs/VIS down to
IFR thresholds throughout the night. CIGs likely more VFR as you get
further south in the Willamette Valley (KEUG) since the front is
tracking towards far northwest Oregon and western Washington. Winds
will gradually get breezier and turn more southerly to southwesterly
early Saturday morning, with gusts up to 30-35 kt along the coast
and 20-25 kt across the Valley. There is also potential for low
level wind shear across the eastern Portland Metro at 2000 ft around
06-12z Sat as southwesterly winds increase aloft and winds at the
surface remain southeasterly.

After 18-21z Sat, the front exits the region and rain transitions
into post-frontal showers. Shower activity will gradually decrease
throughout the afternoon, with CIGs and VIS trending back toward
predominately VFR. Winds Saturday afternoon will also weaken and
turn more westerly behind the front.

KPDX AND APPROACHES...Rain with a mix of MVFR and low-end VFR CIGs
through Saturday morning as the current front pushes through. Low
level wind shear possible between 06-12z Sat as southwesterly winds
aloft increase and winds at the surface remains southeasterly. Winds
turn more southerly after 12z Sat as the front progresses further
inland, with gusts up to 25 kt. Conditions trend more VFR with
decreasing showers Saturday afternoon.        -10

&&

.MARINE...A cold front impinging on the coastal waters this
afternoon will see continued southerly wind gusts hazardous to small
craft, 25-35 kt, easing slightly as the front stalls briefly this
evening. Intermittent gale-force gusts remain most likely north of
Cape Falcon and across the Columbia River Bar this evening, although
without enough coverage or persistence to merit Gale headlines. As a
second system crosses the coastal waters early Saturday morning,
gale-force gusts look to be more widespread inside of 30 NM, and
especially inside of 10 NM including the Columbia River Bar, from 5
AM PDT through the early afternoon, 12-2 PM PDT Saturday. A Gale
Warning has therefore been hoisted across these areas throughout
Saturday morning, while Small Craft Advisories remain in effect
across the outer waters.

As these systems pass over the waters, a long period westerly swell
arriving from the west will see seas rapidly build from 8-12 ft this
afternoon to 15-18 ft by sunrise on Saturday. While gales ease by
Saturday afternoon, seas remain above 15 ft through Saturday
afternoon, supporting Hazardous Seas Warnings remaining in effect
through 8 PM PDT Saturday evening across all coastal waters.

While brief high pressure passes overhead, winds will ease through
early next week, however seas may remain at or above 8-10 ft through
much of the period. Looking ahead to the long-term forecast, chances
for further gusty winds out of the south and attendant rough seas
over 15 ft increase Wednesday into Thursday as another system tracks
into the Northwest.     -36

&&

.BEACH HAZARDS...An increasing westerly swell of 16-20 ft at 16-17
seconds will bring a high threat of sneaker waves this weekend.
Caution should be used when in or near the water. Always keep an eye
on the waves, and be especially watchful of children and pets.
Those participating in razor clam digs should exercise caution.

Elevated swell heights may also bring a marginal high surf threat
from 5 AM to 5 PM Saturday. Destructive waves may wash over beaches,
jetties, and other structures unexpectedly. People can be swept off
rocks and jetties and drown while observing high surf.
Higher than normal water run-up is expected on beaches and low-lying
shoreline. Stay well back from the water`s edge during this time,
and be alert for exceptionally high waves.       -10

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...High Surf Advisory from 2 AM to 5 PM PDT Saturday for
ORZ101>103.

WA...High Surf Advisory from 2 AM to 5 PM PDT Saturday for WAZ201.

PZ...Small Craft Advisory until 5 AM PDT Saturday for PZZ210.

     Gale Warning from 5 AM to 2 PM PDT Saturday for PZZ210.

     Hazardous Seas Warning from 2 PM to 8 PM PDT Saturday for PZZ210-
     251>253.

     Small Craft Advisory until 11 PM PDT this evening for PZZ251>253.

     Gale Warning from 11 PM this evening to 2 PM PDT Saturday for
     PZZ251>253.

     Small Craft Advisory until 2 AM PDT Saturday for PZZ271>273.

     Hazardous Seas Warning from 2 AM to 8 PM PDT Saturday for
     PZZ271>273.
&&

$$

www.weather.gov/portland

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