819
FXUS66 KPQR 191845
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
1045 AM PST Wed Nov 19 2025

Updated aviation discussion.

.SYNOPSIS...Another coastal weather system will brush the area
tonight into Thursday morning bringing light rain, with dry
conditions otherwise expected through the workweek. The pattern
then shifts wetter and colder this weekend into early next week.

&&

.SHORT TERM...Now through Friday Night...Wednesday will see a
cool and dry start, with pockets of valley fog and frost where
skies have remained clear overnight. A dry offshore wind will
help scour out low clouds and fog through the morning,
especially west of terrain gaps including the Columbia River
Gorge, while some areas in the central to southern Willamette
Valley may remain stuck beneath a low overcast into the early
afternoon. Generally seasonable temperatures are expected today,
although areas which remain foggy or cloudy will struggle to
hit even 50 degrees before sunset.

A negatively-tilted trough and surface occluded front will
approach the coast by late this afternoon, before splitting to
form a closed upper low which will dive south into California
on Thursday. Light rain will begin along the coast most likely
by 8-11 PM Wednesday, spreading inland to the I-5 corridor by 10
PM Wednesday-1 AM Thursday, although a reasonable earliest
onset time could be about 2 hours earlier in the evening. As the
developing low tracks southward, rain will become more showery
in distribution and end by the mid-afternoon on Thursday. Given
the expected evolution of this system, highest rainfall totals
will be along the coast, in coastal terrain, and to the south
across Lane County where 0.2-0.5" is expected. The central
Oregon coast including coastal Lane County will be the most
likely to see 0.5" of rain or more. Interior areas from Linn and
Benton Counties northward are more likely to see 0.05-0.15" of
rainfall, although the Cascades may see higher precipitation
totals as well. Snow levels will remain above 5000 ft through
much of the event, dropping closer to 4500 ft by Thursday
morning. This may allow up to a half inch of snow to accumulate
at Willamette and Santiam Passes, but little in the way of
travel impacts are expected.

In the wake of the departing upper low, broad but low-amplitude
ridging will develop over much of the western half of the
country on Friday. This will keep the mid-latitude jet and
primary storm track pointed toward Vancouver Island. Rain
chances will therefore be higher across western Washington and
decreasing southward into western Oregon, leaving much of the
region on the drier side to end the workweek. -36


.LONG TERM...Saturday through Tuesday...This weekend into early
next week, the ridge axis will slowly slide eastward toward the
Rockies, allowing the storm track to dip south into the Pacific
Northwest and resulting in steadily increasing chances for
precipitation across the region. Global ensembles remain in
fairly good agreement given the lead time that an upper-level
shortwave trough will track toward western Washington or
northwestern Oregon, although the timing of this feature
remains more uncertain, ranging anywhere from Sunday night
through Tuesday. Additionally, the ensemble mean mid-level
temperatures overhead have continued to trend warmer through the
period in question, supporting a scenario where even if
plentiful moisture and synoptic lift are present, the column
may simply be too warm to see impactful snow at pass-level. As
such, the chances for 6 inches or more of snow have fallen
substantially to 5-10% at the Cascade passes from Sunday through
Tuesday. On the heels of this shortwave, however, another shot
of colder temperatures could reach the region toward the middle
of next week. -36


&&

.AVIATION...High pressure lingers but fog and low stratus remain
within the region. Areas most impacted are within the Willamette
Valley from KUAO southward. While conditions are improving,
overall there continues to be a fog threat within the southern
Willamette Valley. Around KEUG, the dissipation time is less
certain due to light winds however once winds shift to the south
it should quickly erode. In the north, gusty east winds continue
to blow due to the high pressure. Around KTTD, gusts around 30 kt
have been reported and locally higher winds have been observed
between 1000-3000 ft.

A front is nearing the coast which will cause the ridge to break
down, skies to fill, and will bring precipitation. Widespread MVFR
CIGs are expected after 04Z Thu but there may be pockets of VFR
or high-end MVFR within the interior lowlands. Rain is expected
with locally breezy winds with the front.

KPDX AND APPROACHES...VFR through the next several hours ahead of
a frontal system. Easterly winds will continue to ramp up with
chances for LLWS from the Columbia River Gorge. At this point
there is a chance that the LLWS mixes down and therefore is no
longer a threat, but based on area observations, there is a high
probability. Overnight, MVFR CIGs are most likely with a 20-25%
chance of IFR CIGs between 09-12Z Thu. Due to the low probability
have omitted from the TAF and trended slightly higher to low-end
MVFR. -27

&&

.MARINE...Fairly tranquil conditions in place early this morning
with regional buoys reporting 5 ft seas at light east winds of
5-10 kt, although locally stronger winds may exist west of gaps
in coastal terrain. Winds will turn out of the south and build to
around 20 kt gusting to around 25 kt through this afternoon ahead
of an approaching frontal boundary while seas build to 6-8 ft with
a dominant west-northwest swell. Small Craft Advisories will go
into effect at 1 PM across the outer waters beyond 10 NM, and at 7
PM across the inner waters due to these gusty south winds.

While south to southeast winds will ease to around 10 kt through
tonight, a rapidly building long-period westerly swell will see
seas climb to 16-19 ft by Thursday afternoon and evening. As
such, Hazardous Seas Warnings have been hoisted across the coastal
waters from 10 AM Thursday through 4 AM Friday, spanning the time
when seas are forecast to remain above 15 ft. At the same time,
steep seas of 10-14 ft will make for a hazardous crossing of the
Columbia River Bar, especially during a strong ebb tide Thursday
afternoon, coinciding with some of the highest seas. A Small
Craft Advisory is therefore also in effect for the bar from
midday Thursday through Thursday night.

The long-period westerly swell will ease on Friday, but remain at
10-12 ft into early next week, allowing elevated seas to persist
through at least Monday. Southwesterly winds around 10 kt will
also continue through Sunday before turning out of the north at
10-15 kt on Monday. -36

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory from 10 AM Thursday to 4 AM PST Friday
     for PZZ210.
     Small Craft Advisory from 7 PM this evening to 10 AM PST
     Thursday for PZZ251>253.
     Hazardous Seas Warning from 10 AM Thursday to 4 AM PST Friday
     for PZZ251>253-271>273.
     Small Craft Advisory until 10 AM PST Thursday for PZZ271>273.
&&

$$

www.weather.gov/portland

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