054
FXUS66 KPQR 101103
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
403 AM PDT Fri Oct 10 2025

.SYNOPSIS...
Cooler and cloudier conditions will persist through the weekend
and into early next week as a series of low pressure systems
traverse the northeast Pacific. The first system offshore will
maintain periodic rain chances through the remainder of the
week, followed by another low dropping south from Canada early
next week that will reinforce the cool, unsettled pattern. Light
snow accumulations are possible across the Cascade passes
beginning late Saturday night and continuing into early next
week, though significant impacts are not anticipated at this
time.

&&

.DISCUSSION...Now through Thursday...The region remains locked
in a cool and damp pattern as a broad upper-level trough
dominates the northeast Pacific. Satellite imagery early this
morning depicts a well-defined closed low centered offshore near
43.5N / 131W, with extensive cloud cover extending inland across
northwest Oregon and southwest Washington.

This system will remain nearly stationary through Friday before
slowly drifting eastward, sending periodic shortwaves and
moisture plumes across the area. The first of these disturbances
will bring widespread light to moderate rainfall later today
into Saturday morning. Rainfall totals through Friday night are
expected to range between 0.30 to 0.50 inches across the
interior lowlands and 0.50 to 0.75 inches for the coast, Coast
Range, and Cascade foothills. Probabilistically for 24 hour rain
accumulation to exceed 0.50 inches on Friday, there is a 20-40%
chance for most of the Willamette Valley and a 60-80% chance at
the coast, Coast Range, and Cascade foothills. As for chances
to exceed 0.75 inches within 24 hours, there is a 10-20% chance
within the Willamette Valley and a 30-50% chance at the coast,
Coast Range, and Cascade foothills.

By Saturday, the closed low begins to deepen along the Oregon
coast and pivot inland, producing another round of widespread
rain early in the day. Showery conditions will then develop
through Saturday night and Sunday as the system transitions
eastward. Additional rainfall amounts between 0.50 to 0.80
inches are expected for the valleys, 0.60 to 1.25 inches for
coastal and Cascade zones, and up to 1.50 inches at higher
Cascade elevations. Probabilistically for 48 hour rain
accumulation to exceed 0.80 inches on Saturday and Sunday, there
is a 30-50% chance for most of the Willamette Valley and a
60-80% chance at the coast, Coast Range, and Cascade foothills.
As for chances to exceed 1.25 inches within 48 hours, there is
a 10-20% chance within the Willamette Valley and a 30-50% chance
at the coast, Coast Range, and Cascade foothills.

As the system exits late Sunday into Monday, a colder post-
frontal air mass will overspread the region. Temperatures will
fall into the low to mid-50s for most lowland areas, while
higher elevations and the upper Hood River Valley may dip into
the 30s. Frost advisories may become necessary for some
sheltered Cascade valleys if skies partially clear. At the
moment, Tuesday into Wednesday will be the next day for
clear skies.

Snow levels are expected to lower to near 4000 to 5000 feet
early Sunday through Monday, resulting in light snow
accumulations along the passes. A trace to around 1 inch of wet
snow is expected near pass level, while elevations above 5000
feet could see 3 to 6 inches. For pass level, there is a 40-60%
for snow accumulation to exceed 1 inch within 24 hours from
Sunday into Monday. There remains a 10-30% probability of
higher totals (6-12 inches) at the highest elevations, which
could pose travel issues on unmaintained mountain roads.

Model ensemble guidance continues to show strong agreement that
another low-level low will drop southward from Canada late
Sunday into Monday, keeping rain and Cascade snow chances in
place through at least Monday. However, by midweek, ensemble
means indicate the low shifting eastward and placing the region
between a ridge offshore and the departing trough inland. This
will favor a period of relatively higher pressure and drier
conditions Tuesday through Thursday, with PoPs generally 10-20%
and little organized precipitation expected.

By Thursday into Friday, some ensemble members rebuild the
offshore low and nudge it back toward the coast. If this occurs,
weak onshore flow and increasing cloud cover could return, with
PoPs rising into the 30% range. Confidence remains low for this
late-week scenario, as models continue to define the positioning
and strength of the returning trough.
~12

&&

.AVIATION...Another band of rain moves across the airspace,
currently located over Tillamook OR and Corvallis OR. This
rain band will continue to move northward/northeastward, with
rain expected to arrive at the Portland/Vancouver metro by 12-15Z
Friday. There is low to moderate confidence regarding expected
deteriorated conditions from this rain.

Specifically from now until 18-20Z Friday, there is 50-70% chance
for MVFR conditions and a 30-50% chance for IFR/LIFR conditions
at KEUG. Chances look to decrease to the north, with only a 20-40%
chance for MVFR conditions and a 10-20% chance for IFR/LIFR
conditions at KSLE and KUAO. Around the Portland/Vancouver metro,
chances decrease even more, with a 40-60% chance for MVFR
conditions and less than 10% chance for IFR/LIFR. As for the
coast, KONP and KAST has a 20-40% chance for MVFR conditions
through most of the day, with one exception being KAST having a
40-60% chance for MVFR conditions as the rain band passes between
12-18Z Friday.

Otherwise, expect mostly light and variable winds this morning,
becoming prominently southerly and increasing to 5-10 kt, with
gusts up to 20 kt possible along the coast.

KPDX AND APPROACHES...VFR conditions through most of the TAF
period. Guidance suggests a 30-50% chance for MVFR conditions
between 15-21Z Friday. Rain will persist through much of the
morning and afternoon, and is not expected to affect visibility.
Expect light and variable winds through the period, becoming
mostly southerly by the afternoon.
~12

&&

.MARINE...A low pressure system continues to spin off the
southern Oregon coast near 43.5N, 131W. Southeast offshore winds
will continue through Friday morning, then shift southerly through
Saturday morning. Stronger southerly winds are possible today
along the inner coastal waters and in the outer waters from Cape
Foulweather to Florence OR, but low confidence for wind gusts to
reach or exceed 21 kt.

The low pressure system will weaken further tonight as it moves
onshore by Saturday. Southwesterly winds Saturday morning turn
northwest later in the day. These northwest winds are expected to
increase to 15-25 kt, with gusts potentially up to 30 kt,
strongest across the northern coastal waters. As a result, have
issued Small Craft Advisories to begin Saturday afternoon/evening
for all the waters. Hazardous Seas remain possible from Cape
Shoalwater WA to Cape Foulweather OR beginning late Saturday, but
confidence for location and timing remains low at this time.

An incoming northwest swell will likely push seas up to around 10
to 12 ft late Saturday into Sunday. Another weak low pressure
system approaches the coastal waters from the north late Sunday
into Monday. This low is expected to quickly drop south through
the waters early next week, with northerly winds returning by
Tuesday. ~12/02

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 5 PM this afternoon to 11 PM PDT this
     evening for PZZ210.

     Small Craft Advisory from 5 PM to 11 PM PDT Saturday for PZZ210-
     251>253-272-273.

     Small Craft Advisory from noon to 8 PM PDT Saturday for PZZ271.
&&

$$

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