202
FXUS66 KPQR 211735 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
935 AM PST Fri Nov 21 2025

Updated aviation discussion and hazards.


&&

.SYNOPSIS...Largely dry weather is expected into the weekend as
a ridge of high pressure builds in over the region. This
pattern will favor overnight fog and frost development. A
pattern shift early next week will favor conditions turning
wetter.

&&

.SHORT TERM...Now through Saturday Night...Weak high pressure will
continue to build over the PacNW today. This will result in
generally clear skies overhead. Given the clearing skies, lighter
winds, and ample surface moisture, fog/frost development within
the Willamette Valley is highly likely. Current surface
observations are already showing various locations with 1/2 mile
visibility or less. Given that, have issued a Dense Fog
Advisory for the Willamette Valley through 10 am Friday morning.
Also, surface observations are showing temperatures near
freezing which is supportive for frost development into the
morning hours. As the ridge continues building inland through
Saturday, expect a rinse and repeat for most locations of
overnight and morning fog and frost. However, some locations may
not break out of the fog at all by this afternoon or Saturday
afternoon, especially in the southern Willamette Valley where
very light winds will allow fog to become trapped. These
locations may see high temperatures each day only in the 40s as
the clouds will limit surface heating, with other locations
warming into the low 50s.

Ensemble guidance continues coming into better agreement that
ridging will become more zonal through Saturday.  -42



.LONG TERM...Sunday through Thursday...An upper level
trough looks to move inland around Vancouver Island on Sunday
and slowly drag an associated cold front across the Pac NW. At
the same time a broad area of low pressure over the Great
Basin, will aid in the funneling of some warm, tropical moisture
associated with a weak atmospheric river. Current GEFS and
ECWMF runs are showing IVT values around 250 kg/(ms). This would
slowly funnel a stream of moisture into the WA and northern OR
coast with a 30-60% chance of rain hovering in this region
through the day Saturday. As Sunday approaches, a relatively
stronger, upper level low will finally push this moisture
inland, bringing a round of widespread rain through Sunday
afternoon, before becoming more showery through Monday. Rain
totals from Saturday night through Monday evening range from
amounts will once again be on a low side with 0.30-0.90 inches
along the coast and terrain and 0.15-0.40 inches for the inland
valleys.

Colder air will return to the region behind this frontal system
Sunday night into Monday night, especially as a shortwave ridge
builds over the eastern Pacific and along the coast into Tuesday.
This will bring about another round of frosty overnight conditions
with 50-80% chance of morning low temperatures falling below 36
degrees. Currently, the coldest night at this time looks to be
Monday night into Tuesday morning. Daytime temperatures on
Tuesday also look to be on the chilly side with the majority of
the CWA struggling to reach 50 degrees.

In terms of precipitation, guidance becomes more uncertain as we
move into the middle of next week and beyond. Some ensembles
indicate a weak weather system could undercut the ridging
sometime on Tuesday or Wednesday, leading to increasing
precipitation chances. With colder air expected to be in place,
there is a low probability that near freezing temperatures along
with a 15-30% chance of precipitation could result in a mixture
of rain/snow to be observed. However, probabilities for any
accumulating snow (greater than 0.01 inch) are near zero, so if
any snow does fall, it would be flurries or slushy rain. Once we
move into Wednesday and beyond, warmer temperatures are expected
to return along with another round of warm precipitation for the
Pac NW. It should be noted that exact timing and precipitation
amounts for the latter part of next week are still unknown. So,
those who are planning on any travel for the upcoming holiday
should pay attention to the forecast and remain as flexible as
possible in their plans. -42


&&

.AVIATION...High pressure over the area will lead to a mixture of
VFR and IFR conditions today. This morning dense fog lingers in
the central and southern Willamette Valley with LIFR stratus of a
200 ft AGL. Conditions will remain stagnant until later in the
morning/early afternoon when the sun eats away at the stratus. A
limiting factor is that there is a high stratus shield which may
insulate enough to keep it socked in around KSLE and KEUG.
Elsewhere VFR conditions persist - especially along the coast
where winds are easterly. Through the day skies will clear with
VFR conditions but will be short lived as the high pressure will
lead to yet another round of fog late tonight into early Saturday.
There is high confidence in widespread dense fog with VIS less
than 1/4 SM throughout the Willamette Valley and coastal gaps.
There is around a 30% chance in the lowlands north of KUAO but
with this pattern, models sometimes struggle to realize this small
scale feature. Fog will likely remain through the morning on
Saturday.

KPDX AND APPROACHES...IFR in low stratus but generally focused
right at the terminal and not on the approaches - especially from
the east. This low stratus will burn off but it may take several
hours due to a lack of wind. VFR conditions return but will once
again fall overnight. There is a 30-50% chance of IFR conditions
returning again tonight after 08Z Sat. Temperatures will lower
tonight once again but freezing is not expected. -27

&&

.MARINE...A ridge of high pressure continues to builds over the
region, which is resulting in winds generally less than 10 kt
through the remainder of the week. On Sunday, a fast moving
frontal system on Sunday will result in increasing southerly winds
on Sunday before turning northwesterly by Sunday evening/night as
a frontal system crosses the waters. A strong west/northwest
swell will keep seas 9-14 feet at 12-16 seconds through at least
early Monday morning. As a result, will maintain the current suite
of Small Craft Advisories up through at least early Monday
morning. An active weather pattern continues through much of next
week. -42

&&

.BEACH HAZARDS...
An energetic westerly swell is expected along
the northwestern Oregon and southwestern Washington coasts for a
long duration through Monday. Seas 9-14 ft at 12-16 seconds
through the the weekend. These energetic waves can run significantly
farther up a beach than normal, including over rocks and jetties,
creating potentially life-threatening conditions in the surf zone
when beachgoers can be unexpectedly knocked off their feet and
pulled out into cold ocean waters.

A Beach Hazards Statement has therefore been issued through 5 AM
Monday. Caution should be used when in or near the water, and
beachgoers with children should be especially watchful. Never turn
your back on the ocean, and be sure to keep an eye on the waves.
Those participating in razor clam digs should additionally
exercise caution. -42

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Dense Fog Advisory until 1 PM PST this afternoon for
     ORZ114>118.
WA...None.
PZ...Small Craft Advisory until 4 AM PST Monday for PZZ210-251>253-
     271>273.
&&

$$

www.weather.gov/portland

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