345
FXUS66 KPQR 270527 AAA
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
927 PM PST Wed Nov 26 2025

Updated Aviation and Marine discussions

.SYNOPSIS...Wet conditions continue through Thanksgiving as
another frontal system impacts the region bringing additional
widespread rain and breezy winds. Conditions gradually trend
drier Friday into Saturday with showers largely pinned to higher
terrain features. Snow levels drop to the passes by Saturday
but limited accumulation is anticipated. A cooling trend impacts
the region Sunday into early next week with additional chances
for precipitation arriving on Tuesday.

&&

.DISCUSSION...Now through Tuesday night...Current radar and
satellite observations show our current swath of rainfall
slowly shifting northward late this afternoon with the south
Willamette valley beginning to see a break from the rainfall.
This northward trend in the precipitation continues into the
evening/overnight hours, and confidence is high we`ll
experience a region wide lull in the rainfall until the next
frontal system arrives from the west Thursday morning. Both
ensemble and deterministic guidance continue to indicate that
the center of this low pressure system likely makes landfall
somewhere just north of Astoria, OR along the Washington
coastline Thursday evening. Rain amounts with this system are
expected to somewhat similar to the previous front with 0.2-0.45
inch for the central and southern Willamette Valley, 0.4-0.75
for the northern Willamette Valley into the SW Washington
lowlands, 0.5-1.5 inches along the coast and Coast Range, and
Oregon Cascades south of Clackamas County, and 0.8-2 inches for
the north Oregon and SW Washington Cascades. Snow levels will
remain just above pass level with this second system as well.

Winds are also expected to increase as the front and low
pressure center move inland. Expect winds along the coast to
begin increasing Thursday morning, then inland areas Thursday
afternoon as the aforementioned low finally onshore tightening
pressure gradients near the surface. There are some
discrepancies between the various sets of guidance as to just
how breezy winds will get with the NBM markedly lower than high
resolution ensembles like the HREF and REFS. Given that winds
aloft are expected to be elevated (~40-50 knots at 850 mb) with
neutral to slightly unstable conditions present in the boundary
layer to facilitate vertical mixing Thursday afternoon, nudged
wind/wind gust values towards the high resolution ensemble
means. With this in mind expect peak gusts of 35-45 mph along
the coast and Cascades crests, and up to 25-38 mph for inland
valleys (highest Salem to Portland). However, it`s worth
highlighting there is a 15-25% chance for peak gusts to exceed
45 mph in the north Willamette Valley into the
Portland/Vancouver Thursday late afternoon and evening which
would cause additional impacts. We`ll need to watch the
progression of this low pressure closely. High confidence winds
decrease Thursday night into Friday.

The weather on Friday into Saturday looks pretty benign other
than shower chances continuing. Ensemble guidance is in good
agreement of a strong upper ridge beginning to build in the
eastern Pacific through the weekend. A good number of ensemble
members and their deterministic counterparts continue to
suggest a weak shortwave will move along the flow aloft over
the PacNW on Saturday, which is stretching out the chances for
precipitation. However, there still remains decent uncertainty
in the exact location of the shortwave, whether it will move
over western WA and OR, or more to the east in eastern WA, OR,
and into Idaho. This will affect exactly how much cooler air
will funnel into NW Oregon and SW Washington. If the wave is
more to the west, more colder air will move into NW Oregon and
SW Washington. If the wave is more to the east, the coldest air
will remain east of the Cascades. Latest NBM guidance indicates
cooling Sunday morning with Monday morning being the coldest.
Sunday morning has a 20-50% chance of low temperatures falling
below 32 degrees with probabilities increasing to 40-80% for
Monday morning. The highest probabilities are in typical colder
spots outside of urban areas, especially in the Willamette
Valley between Corvallis and Eugene. One thing to note is
probabilities of sub-freezing temperatures around the Portland
metro area are only around 10-25% for each day. When looking at
the probability of temperatures falling to 25 degrees (Cold
Weather Advisory criteria), most lowland locations are below
10%, though the cold pocked in the central/south Willamette
Valley mentioned earlier has around a 15-25% chance.

By Tuesday, ensembles are in agreement that a slightly stronger
shortwave and associated frontal system will slide south from
western Canada into the PacNW, breaking down the high pressure
over the region and returning precipitation chances over the
area. Quite a bit of uncertainty exists in the strength of this
system and the impacts associated with it, though cold weather
could stick around in the wake of it. -99/03

&&

.AVIATION...A warm front lifting north will bring a brief break in
the rain overnight. But, weak ridging aloft and clearing skies are
allowing for fog and low stratus to develop across much of the
Willamette Valley this evening. As of 04z Thursday, LIFR
conditions have developed from KEUG to KUAO and will likely
persist through 10-12z. Expect similar conditions to develop after
06z across northern portions of the Willamette Valley as the
higher clouds and light drizzle push farther north. An approaching
cold front will push another round of rain onshore around 09z Thu,
spreading inland early Thu morning. Expect conditions to trend
toward predominately MVFR through Thursday evening. Southerly
winds are also expected to increase as the low pressure system
moves closer to the south Washington coast on Thursday, with wind
gusts up to 35 kt along the coast and up to 25 kt inland by late
Thu afternoon.

KPDX AND APPROACHES...As of 04z Thu, light rain ending as the warm
front lifts north. Clearing conditions will likely be brief as low
stratus and possibly fog develop. But, breezy east winds near KTTD
could potentially maintain VFR conditions overnight. Guidance
suggests around a 40% chance of MVFR CIGs at the PDX terminal
through 10-11z, before the probabilities increase toward 80% with
the return of rain by around 11-12z. Southeast winds around 8-10
kt expected to increase through Thursday, with gusts up to 25 kt
later Thu afternoon and evening. /DH

&&

.MARINE...A warm front will continue to lift north overnight while
southerly winds increase across the coastal waters tonight through
Thursday. A 996 mb low pressure system currently located about 450
miles west of the mouth of the Columbia River will move toward the
south Washington coast through Thursday evening. An initial cold
front is expected to move across the coastal waters Thursday
morning, with isolated wind gusts up to 35 kt. More widespread
gales are now expected behind the front, with south to
southwesterly winds increasing through Thu afternoon, with wind
gusts up to 40 kt likely. Seas will also increase, becoming steep
and hazardous through Thu evening, peaking around 15 to 18 ft at
11-13 seconds late Thu afternoon through Thu evening. There
remains around a 10% chance that significant wave heights reach 20
ft. Gale warnings are in place for all waters later Thu morning
into Thu afternoon, and transition into hazardous seas to cover
the large fresh swell that will move into the waters later
Thursday. Conditions ease late Thursday night into Friday as the
low weakens, with seas expected to fall below 10 ft by Friday
afternoon. Hazardous conditions are not expected through the
weekend as weak high pressure builds over the waters. /DH

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 1 AM to 11 AM PST Thursday for PZZ210-
     251>253.

     Gale Warning from 11 AM to 6 PM PST Thursday for PZZ210-251>253.

     Hazardous Seas Warning from 6 PM Thursday to 2 AM PST Friday for
     PZZ210-251>253-271>273.

     Small Craft Advisory until 7 AM PST Thursday for PZZ271>273.

     Gale Warning from 7 AM to 6 PM PST Thursday for PZZ271>273.
&&

$$

www.weather.gov/portland

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