472
FXUS66 KPQR 281120
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
420 AM PDT Mon Sep 28 2026

.SYNOPSIS...Dry weather continues today with temperatures near
seasonable norms. Then on Tuesday a weakening frontal boundary
moving into the region from the northwest brings the next
chance for rain through early Wednesday morning with the
highest probabilities along the coast, Coast Range, and
Washington/North Oregon Cascades. Dry weather is favored again
by Wednesday afternoon through the latter half of the week into
next weekend.

&&

.DISCUSSION...Now through Sunday...Expect a weak ridge of high
pressure to remain overhead for one final day helping to
facilitate dry conditions. Ample clearing headed into the
sunrise hours this morning has allowed for patchy fog to form in
some of the Coast Range Valleys and sheltered pockets of the
Willamette Valley locally reducing visibility. As daytime
heating gets underway, any patchy fog inland will quickly
dissipate by the late morning hours followed by mostly clear
skies with high clouds increasing later in the day. High
temperatures will once again rise into the low 70s across the
interior lowlands - close to average for late September. Enjoy
days like these while they last, although it`s likely we`ll see
the return of comparable conditions by the end of the week.

Our next noteworthy change to the weather pattern arrives on
Tuesday as a upper-level trough and weakening frontal boundary
move into the Pacific Northwest. Precipitation chances increase
substantially along the north Oregon Coast and Coast Range into
southwest Washington and the North Oregon Cascades with
probabilities for rainfall around 60-90% Tuesday during the day
before gradually decreasing Tuesday night into Wednesday
morning. Farther inland, confidence in measurable rainfall
remains much lower, with only around a 10-30% chance for
measurable rain (>0.01) from the Portland metro through the
Willamette Valley during this time period. However, just to the
north, there is a 45-70% chance of at least measurable rainfall
from Battle Ground to Longview. Most inland valley locations
should therefore remain dry outside of a few trace amounts of
rain here and there. You`ll find the best chances for completely
dry weather the further south you go (generally south of
Salem).

Once the frontal system passes late Tuesday night dry conditions
are expected to return as Wednesday morning progresses, with dry
weather holding in place the remainder of the week into the
weekend. Deterministic and ensemble modeling systems still show
a bit of dissonance resolving the large scale pattern Thursday
into Friday, mainly regarding a weak shortwave feature which
has the potential to graze the region during this time period.
That said, the vast majority (85%+) of the ensemble members now
keep this shortwave far enough to our north to shunt any light
rainfall out of our CWA. By next weekend, most models begin to
hint at a more pronounced ridge of high pressure building
overhead although there is still decent uncertainty in the exact
amplitude and placement of this feature which will heavily
impact just how warm temperatures may get. -99/12

&&

.AVIATION...Through 12Z Tuesday...Mainly VFR conditions
expected through the TAF period yet again. Mostly clear skies
and light winds continue to persist for the inland terminals
this morning, although we`ll have to watch for isolated pockets
of fog nearing sunrise (20-25% chance for IFR conditions at
KEUG, 5-10% elsewhere). At the coast, marine stratus is
gradually forming, likely expanding over the next several hours
and bringing a 50-80% chance for MVFR or lower CIGs to KAST and
KONP through 18-20z today. Winds increase slightly along the
coast to 6-10 kt from the west/northwest after 18z, turning
southerly by the evening and overnight.

KPDX AND APPROACHES...VFR conditions with light winds less than
5 to 8 kt are anticipated through the TAF period. -99

&&

.MARINE...Expect fairly benign conditions through the daytime
hours today as a frontal boundary begins to approach the coastal
waters. Lingering northerly winds switch southwesterly and
increase by the evening. This frontal feature finally moves
through the waters the second half of Tuesday. There are high
chances (70-90%) of wind gusts exceeding 21 kts (Small Craft
Advisory criteria) Monday evening into Tuesday for the coastal
waters north of Cape Foulweather, with gusts most likely peaking
around 25-30 kts. Once the front passes, northerly winds return
Tuesday night through the middle of the week. A longer period
west to northwesterly swell of 5-8 ft at 12-16 seconds will also
move into the coastal waters late Monday through Wednesday,
resulting in a moderate sneaker wave threat and increasing
significant wave heights into the 6-10 ft range. While seas
gradually fall into the end of the week, models hint at the
arrival of another WNW swell around Saturday. -99/03


&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory from 11 PM this evening to 5 PM PDT
     Tuesday for PZZ210.
     Small Craft Advisory from 8 PM this evening to 5 PM PDT
     Tuesday for PZZ251-271.
     Small Craft Advisory from 5 AM to 5 PM PDT Tuesday for PZZ252-
     272.
&&

$$

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