099
FXUS66 KPQR 271044
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
244 AM PST Thu Nov 27 2025

.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...Thursday morning through Wednesday...The forecast
remains on track from the previous forecast package with very
little change. Satellite imagery early Thursday morning depicts
a compact low pressure system located around 400 miles west of
the WA/OR border with a cold front approaching the WA and OR
coast. Radar imagery shows the band of rain associated with the
cold front moving inland along the coast. The cold front will
move inland through the morning hours, reaching the Cascades by
midday, as the closed low approaches the coast.  Ensemble
guidance is in very good agreement that the low will approach
the coast right around or just north of the WA/OR border late
this afternoon, then slowly weakening and dissipating over the
coastline tonight. Widespread rain will push east of the
Cascades by midday with conditions turning showery for the
afternoon and evening, continuing into Friday morning as the
upper trough associated with the frontal system exits the region.
Rain amounts with this system through Friday morning will be
similar to previous weather systems. Expect 0.15-0.45 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 as well as the
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 expected to be the main impact with this system. As
the front moves inland, winds will begin increasing along the
coast this morning and inland this afternoon. Strongest winds
will be late this afternoon through this evening as the low
center reaches the coast and pressure gradients tighten east of
the low center. Some discrepancies remain between the various
sets of guidance as to just how breezy winds will get. The NBM
remains 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 25-35 mph for inland valleys (highest Salem to Portland).
However, it`s worth highlighting there is a 10-25% chance for
isolated peak gusts to exceed 45 mph in the north Willamette
Valley into the Portland/Vancouver late afternoon and evening
which would cause additional impacts. We`ll continue to watch
the progression of this low pressure closely. There is high
confidence that winds decrease late tonight into Friday.

Ensemble guidance remains in good agreement that a strong upper
ridge will build in the eastern Pacific Friday afternoon through
the weekend, though a shortwave will move along the flow on
Saturday, producing a slight chance of showers, mainly over the
terrain. Then cold air is likely to funnel into the PacNW behind
this shortwave.

However, uncertainty in the exact location of the shortwave
continues amongst the ensembles, 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
less cooling on Sunday morning then previous forecasts with
mainly a 20-40% chance of low temperatures falling below 32
degrees except for up to 50% chance in the Willamette
Valley between Corvallis and Eugene. Monday morning still looks
to have the coolest temperatures with a 40-80% chance of low
temperatures falling below 32 degrees, with highest
probabilities 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
5-15% for each day. Probability of temperatures falling to 25
degrees (Cold Weather Advisory criteria) have also decreased
with most lowland locations below 5%, and the cold pocked in
the central/south Willamette Valley mentioned earlier around a
10-25% chance.

By Tuesday, ensembles remain 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 through Wednesday. 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...At 10z Thu, observations indicate that the fog and
stratus that formed in the Willamette Valley during the break
between fronts continues with conditions fluctuating between
MVFR/IFR/LIFR cigs and vis. Additionally, radar imagery shows a
widespread band of rain moving inland along the coast. As this
rain continues moving east, reaching inland terminals by 11-13z
Thu, the fog and stratus should mix out. However, conditions
trending predominately MVFR through the day Thursday, though
periods of IFR cigs are possible as the band of rain moves over
terminals between 11-15z Thu. Southerly winds are also expected
to increase today as a low pressure system over the eastern
Pacific moves closer to the south Washington coast, with wind
gusts up to 35 kt along the coast after 15z Thu and up to 25-30
kt inland after 20z Thu.

KPDX AND APPROACHES...Predominately MVFR conditions continue
through the period with the return of rain by around 11-12z Thu.
Brief periods of IFR cigs are possible in heavier rain through
15-16z Thu. Southeast winds around 10-14 kt expected to increase
through Thursday, with gusts up to 25-30 kt after 20z Thu. -03

&&

.MARINE...A closed 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, causing
winds to increase during the day. 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 as the closed low pressure system moves
through the waters. South to southwesterly winds will continue
increasing through Thursday afternoon, with wind gusts up to 40
kt likely. Seas will also increase through the day, becoming
steep and hazardous Thursday afternoon through evening, peaking
around 15 to 18 ft at 11-13 seconds. 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/03

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 11 AM PST this morning for PZZ210-
     251>253.

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

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

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

     Gale Warning from 7 AM this morning to 6 PM PST this evening for
     PZZ271>273.
&&

$$

www.weather.gov/portland

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