787
FXUS66 KPQR 110530
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
930 PM PST Mon Nov 10 2025

.SYNOPSIS...A weak shortwave trough continues to pass through
the region today, bringing scattered light showers and mid-level
clouds across northwest Oregon and southwest Washington.
Conditions will briefly dry out on Tuesday as high pressure
builds. By Wednesday morning, the weather pattern turns cooler
and wetter as a deeper system approaches from the northeast
Pacific. Snow levels will fall Thursday into Friday, allowing
for accumulating snow at Cascade passes. Unsettled weather is
expected to continue through the weekend.

&&

.SHORT TERM...Now through Wednesday...A weak front brushing
the area is producing light precipitation mainly along the
Cascade foothills this afternoon. Additional measurable rainfall
through this evening remains possible, with the greatest
likelihood across southwest Washington and the Cascades, while
lower chances exist west of the mountains. Winds are light and
variable this afternoon, generally around 5 mph from the south
to southwest, shifting to northwesterly by evening. On Tuesday,
a shortwave ridge builds in, producing some clearing and drier
conditions in the morning. This temporary lull gives way late
Tuesday night as a deep upper-level trough approaches from the
northeast Pacific. A cold front associated with this system will
cross the region on Wednesday afternoon, bringing widespread
rain. The heaviest precipitation is expected along the coast and
Coast Range, with more moderate totals in the interior valleys.
Probabilistically for 1 inch or more of rainfall from 4 PM
Wednesday to 4 PM Thursday, there is a 15-30% chance within the
interior valley and a 50-70% along the Coast and Coast Range.
Snow is also possible in the Cascades Wednesday into Thursday,
though amounts remain uncertain.


.LONG TERM...Thursday through Sunday...Snow levels are expected
to fall Wednesday night into Thursday morning, though model
guidance remains inconsistent, ranging from as high as 8,000
feet to as low as 3,500 feet. This uncertainty translates to low
confidence in specific accumulation amounts. Current guidance
suggests that between Wednesday afternoon and Thursday
afternoon, there is a 30-50% probability that snow totals could
reach 1 inch or more and a 10-20% probability that snow totals
could reach six inches or more, clearly reflecting the
uncertainty in snow levels and timing. Additionally, while the
track of the low pressure system remains uncertain, it is
possible to see gusty winds on Thursday. For chances of wind
gusts above 35 mph on Thursday, there is a 15-30% chance inland
and 30-50% chance along the coast. The coast could even see
isolated wind gusts up to 45 mph as guidance suggests a 10-20%
chance of such wind gusts to occur.

The post-frontal air mass on Thursday will be cooler and
slightly unstable, supporting isolated thunderstorm activity
mainly along the coast, though overall chances have decreased as
CAPE values are marginal. Any passing thunderstorms could
produce lightning, heavy downpours, gusty outflow winds, and
small hail.

Temperatures aloft are trending slightly warmer than previous
guidance, with 850 mb levels dropping to roughly 0-2C Thursday
into Friday, which could place snow levels near Cascade passes,
but with more uncertainty compared to previous guidance. From
Thursday morning into Saturday morning, Santiam and Willamette
Passes have a 40-60% chance of six inches or more of snow, while
areas near Government Camp have slightly lower probabilities.
A warm front lifting north on Saturday will raise snow levels
above pass elevation, and wet conditions are expected to persist
through the weekend as active weather continues. ~12

&&

.AVIATION...A weak front continues to be draped across the region
with mixed flying conditions as a result. Along the NW Oregon and
SW Washington coast on the backside of the front, conditions have
improved to VFR, although a trend toward increased cloud cover
will favor MVFR cigs by 12z Tue. Much of the Willamette Valley
and central OR coast remain beneath the frontal boundary, although
the front is weak enough that precipitation chances are very low
(15% or less). As a result, widespread low cloud cover is yielding
MVFR cigs at 1-2 kft inland and IFR cigs along the coast.

As the front slowly sags southward tonight, conditions may
deteriorate in the southern Willamette Valley and along the
central OR coast as cigs lower even further, while terminals to
the north may see drier northerly flow support enough clearing to
produce areas of fog/mist and resultant reduced vis. Confidence
in the placement of fog/mist remains very low, with the most
likely timing from 12-15z Tue. If low-level cloud remain lodged in
interior valleys, then chances for fog/mist will be minimized. As
the front finally clear the region by Tuesday afternoon and any
remaining low clouds or vis restrictions mix out, VFR conditions
will return to all terminals after 18-21z Tue.

KPDX AND APPROACHES...Pesky MVFR cigs likely to persist while the
frontal boundary remains stalled over the region. Continue to
expect a modest clearing trend after 09-12z Tue, which could allow
for patchy fog/mist to develop by 12-15z Tue, especially near the
Columbia River. If low cloud deck does not clear as expected,
vis restrictions are less likely. Any low clouds/mist will mix out
by 18-19z Tue, yielding VFR conditions through the remainder of
the period. North to northwest winds continue at 5 kt or less.
-36

&&

.MARINE...Benign marine conditions continue through Tuesday
night as weak high pressure builds over the waters. Winds will
remain generally northerly with gusts less than 10 kts. High
confidence (>95% chance) that seas remain below 10 ft at 10-12
seconds.

The next low pressure system in the NE Pacific will return breezy
southerly winds and building seas Wednesday into Thursday, with
high confidence for another period of conditions hazardous to
small craft. As this system swings a front through the waters,
there`s a 60-80% chance of frequent southerly wind gusts
exceeding 21 kt and a greater than 90% chance that seas build
above 10 ft by Wednesday night. There is also a 40-60% chance for
isolated gale- force wind gusts greater than 34 kt Wednesday-
Thursday, with the highest chances across the outer waters beyond
20-30 NM. Active weather continues into the end of the week with
additional systems moving through the waters. -10/03

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

www.weather.gov/portland

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