146
FXUS66 KPQR 161155
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
355 AM PST Sun Nov 16 2025

.SYNOPSIS...Rain returns by this evening as the progressive and
active pattern continues. Through the workweek, repeated
systems will bring cooler temperatures along with multiple
chances for lowland rain and mountain snow to the region.

&&

.SHORT TERM...Now through Tuesday Night...Sunday will feature a
dry start but with a foggy morning for many lowland locales.
Moist low levels beneath largely clear skies has resulted in
ample radiation fog developing early this morning. Observed
visibilities along the coast and through the northern
Willamette, Lower Columbia, and Cowlitz Valleys have sunk below
1 mile, while latest satellite imagery depicts fog or low
stratus clouds also affecting Coast Range Valleys. While the
central and southern Willamette Valley has generally maintained
higher visibility beneath low stratus thus far into the
overnight period, conditions could still support fog development
before sunrise. Areas of dense fog and visibilities below 1/4
mile are most likely in typical fog- prone areas including
sheltered valleys or low spots within larger valleys, as well as
areas near rivers or other water sources. Visibility will
likely improve as diurnal mixing increases in the hours
following sunrise, however additional cloud cover associated
with an approaching frontal system will make it difficult to see
any substantial clearing of low clouds today.

A narrow and elongated upper-level trough over the Northeast
Pacific will swing into the coast this evening as a surface cold
front traverses the region through tonight. Precipitation will
most likely begin by 9-10 AM along the coast, by noon along the
I-5 corridor, and by 2-3 PM in the Cascades. At the earliest,
rain could begin about two hours earlier while at the latest,
its onset could be delayed about two hours later. With snow
levels remaining above 6500 ft through tonight, precipitation
will largely fall as rain in the Cascades aside from the highest
peaks. As the trough moves inland, its base pinches off to form
a cutoff low over California while the remaining rump trough
lifts into southern British Columbia, leaving much of the region
displaced from the best forcing for ascent and therefore
lowering potential rainfall amounts compared to areas to the
north and south. Through tonight, most likely rainfall amounts
remain around 0.3-0.5" along the I-5 corridor and 0.5-1" along
the coast and in higher terrain. In the wettest scenario where
the trough maintains its structure as it moves inland, about a
10% chance of occurrence, higher rainfall totals of 0.5-0.75"
could be observed along the I-5 corridor and 0.75-1.5" along the
coast and in higher terrain.

While the developing split flow pattern will see coverage of
showers decrease through Monday and Tuesday, much cooler air
moving in overhead will see snow levels fall to 3500-4500 ft by
Tuesday morning. By this time, precipitation amounts will be
much lower, so while snow may fall down to Cascade pass-level,
impactful accumulations are not anticipated. Cooler air aloft
will be reflected in surface temperatures with highs likely only
reaching the low to mid 50s for valley areas on Tuesday. Tuesday
night may be the coldest of the season so far for many with lows
expected to fall into the mid to upper 30s for most. -36


.LONG TERM...Wednesday through Saturday...The active pattern
continues through the latter half of the week as another trough
looks to move inland late Wednesday into Thursday, however there
remains significant uncertainty in its evolution, particularly
whether it will follow a similar pattern of splitting into a
cutoff low to the south, thereby leaving northwestern Oregon
and southwestern Washington in a region of weak forcing and
successive forecasts of lower precipitation amounts. As before,
in the scenario of a more coherent trough affecting the region,
the combination of cool air aloft and ample moisture could
support impactful snow accumulations down to pass-level in the
Cascades, although this is an unlikely solution at this point.
Chances for 6 inches of snow Thursday through Friday at the
Cascade passes is a mere 5%. Otherwise, seasonable temperatures
with persistent 25-50% chances of rain showers are favored
across the region through the workweek. Long-range guidance
features low probabilities of another impactful system by next
weekend. -36

&&

.AVIATION...Widespread IFR/LIFR flying conditions early this
morning across the region with fog/mist and low stratus in place.
The majority of terminals will continue to see severely restricted
vis of 1SM or less through 16-18z Sun before improving. KSLE has
maintained VFR vis so far through the overnight period, but there
is a 50-60% chance vis will degrade to at least MVFR by sunrise.
While vis quickly improves as fog/mist mix out, cigs will likely
remain stuck at IFR/low-end MVFR levels for most terminals. Calm
to light and variable winds early this morning will increase to
5-10 kt out of the south after 15-18z Sun.

A cold front arriving from the west will spread rain across the
airspace from 15-21z Sun. At precipitation onset, increased mixing
may actually improve conditions by lifting cigs at inland
terminals, before chances for further IFR cigs increase after 06z
Mon, while along the coast, persistent IFR cigs are expected.
Winds will shift out of the northwest at 5-10 kt behind the
boundary after 00-06z Mon.

KPDX AND APPROACHES...LIFR conditions within fog expected to
persist through 16-17z Sun before improving. While vis may return
to VFR levels, IFR cigs are likely to continue into the early
afternoon. A cold front will arrive from the west, with rain
beginning around 20z Sun and cigs potentially improving to MVFR
at precipitation onset, although IFR cigs are again favored after
06z Mon. South winds around 5 kt through much of the day will turn
out of the northwest behind the front. -36

&&

.MARINE...Seas of 7-9 ft at 13 seconds continue across the waters,
but will build to 9-11 ft by this afternoon and further to 12-15
ft by Monday morning as a frontal system tracks across the region.
A Small Craft Advisory therefore remains in effect as seas remain
elevated through Monday evening. Another frontal system will
traverse the waters Sunday evening into Monday, with initial
southwest winds becoming northwesterly with gusts up to 25 kt
behind the boundary, mainly for the outer waters. A building
westerly swell will cause seas to rise to 12-15 ft by late Sunday
night or Monday morning, before falling below 10 ft early Tuesday
morning. Wednesday into Thursday, yet another system will see
increasing winds and building seas across all waters. The robust
swell expected mid to late this week has a high probability of
exceeding 15 ft, but there is also a 25% chance of 20 ft seas and
a 10% chance of 22 ft seas or higher. -42/36

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.

WA...None.

PZ...Small Craft Advisory until 7 PM PST Monday for PZZ210.
     Small Craft Advisory until 10 PM PST Monday for PZZ251>253-
     271>273.

&&

$$

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