439
FXUS66 KPQR 070522 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1022 PM PDT Sun Sep 6 2026

Updated Aviation and Marine Discussion...

.SYNOPSIS...Lingering rain showers will dissipate Sunday night as an
upper level low centered over central OR shifts eastward. Trending
drier Monday through Wednesday with temperatures gradually warming
each day with the development of low-level offshore flow. Confidence
has increased dry weather will continue through Thursday as well,
with temperatures remaining seasonably warm. The forecast becomes
more uncertain late Friday into Saturday, with the potential for
weather conditions to range anywhere from cool and showery to warm
and dry depending on the evolution of the large scale weather
pattern.

&&

.DISCUSSION...Now through Saturday night...Radar, satellite, and
surface weather observations from early to mid Sunday afternoon
showed rain showers lingering over northwest Oregon and in portions
of southwest Washington to the east of the I-5 corridor. This
precipitation is occurring on the backside of an upper level low
centered over central Oregon. This low will continue moving eastward
Sunday evening and Sunday night, which will bring an end to any
lingering showers. The latest suite of hi-res model guidance suggests
showers will end across the entire area by 10-11 PM Sunday, except in
the far south WA/north OR Cascades and Columbia River Gorge where a
few showers may linger beyond 11 PM into the overnight hours (15-30%
chance).

Come Monday, all locations should be mainly dry as surface high
pressure strengthens over the area. Admittedly, there is a 1-10%
chance for a stray shower on Monday with the passage of a weak upper
level shortwave trough, however any showers that do develop would be
very light and short-lived with limited vertical growth. Most
locations will be dry the entire day, with stray showers having the
highest chance of occurring over the south WA/north OR coast and
Willapa Hills. With skies becoming sunnier Monday afternoon,
temperatures should warm into the low to mid 70s across the interior
lowlands and mid to upper 60s along the coast.

Confidence is high for dry weather and warmer temperatures Tuesday
through Thursday as low-level offshore flow develops. Most inland
valley locations will see high temperatures in the upper 70s to mid
80s each day, warmest on Wednesday. The coast will remain a bit
cooler with highs most likely in the low to mid 70s. That said, even
the coast has a 1-10% chance of reaching 80 degrees or warmer,
specifically on Wednesday when offshore winds have the potential to
last into the early afternoon. Chances for highs in the 80s are
closer to 30% for inland coastal communities such as Astoria and
Tillamook.

Although confidence has increased for dry and warm weather on
Thursday, confidence remains relatively lower late Friday into
Saturday. This is due to model differences regarding the exact
timing, location, and amplitude of an upper level trough that will
attempt pushing into the Pacific Northwest from British Columbia.
Confidence is high that temperatures will trend cooler on Friday
compared to earlier in the week, but is not clear how much cooler as
the full range of outcomes for high temperatures is anywhere from the
lower 60s to upper 70s. The outcome will be highly dependent on how
deep the trough becomes and if it tracks into Washington and Oregon
or further to the east towards the Northern Plains, which will also
determine whether or not rain will return to the area. If rain does
return, highs in the 60s would be expected. If rain does not return,
highs would likely top out somewhere in the 70s, assuming enough sun
breaks occur. Will note the 12Z/September 6 iteration of the LREF has
trended drier on Friday with 80-90% of the total ensemble space from
the ENS/GEFS/GEPS combined showing dry weather and around 75% showing
dry weather on Saturday. The NBM is consistent with this and suggests
only a 10-20% chance of rain late Friday into Saturday. This means
dry weather with highs somewhere in the 70s is currently the most
likely outcome, however anyone with outdoor plans should monitor the
forecast for updates. -23

&&

.AVIATION...Through 06Z Tuesday...With the low pressure system now
moving east out of the airspace, rain has ended at all terminals.
Still, MVFR CIGs continue to impact most terminals as of 05Z Mon and
may continue to do so overnight as there is high confidence that
marine stratus will push into the coast, and possibly inland.
Probabilistic guidance suggests a 20-60% chance of MVFR CIGs
between 06-18Z Mon at inland terminals, with the highest chances
between 12-16Z Mon. As for coastal terminals, there is a 60-80%
chance of MVFR CIGs until 18-20Z Mon, with the exception of a
20-40% chance of IFR and 10-30% chance of LIFR conditions at KONP.
Otherwise, expect generally light and variable winds at most
terminals through the TAF period, with the exception of northwest
winds around 8 kt at coastal terminals during the afternoon.

KPDX AND APPROACHES...Current MVFR CIGs may continue overnight, as
guidance suggests current 20-30% chances of MVFR CIGs to
increase to 50-60% between 12-18Z Mon as stratus may develop.
Expect VFR conditions to return beyond 18Z Mon. Light and
variable winds expected through the period, except for
northwesterly winds tomorrow afternoon. ~12

&&

.MARINE...High pressure offshore will maintain predominately
northerly winds across the coastal waters through the week. A weak
front will bring more variable winds early Monday. A strengthening
pressure gradient on Tuesday will bring stronger northerlies with
gusts possibly up to 25 kt (80% chance of wind gusts exceeding 21
kt by Tuesday evening). As a result, Small Craft Advisories have
been issued from 11 AM to 11 PM Tuesday for all the waters except
for the outer waters (beyond 10 NM) north of Cape Falcon. Breezy
winds continue through Thursday, but should remain 20 kt or less.
Seas at around 3 to 4 ft with a dominant northwest swell at 8-9
seconds will gradually build to around 6 ft late Tuesday. ~12/DH

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 2 PM to 11 PM PDT Tuesday for PZZ210-
     251>253-272.

     Small Craft Advisory from 11 AM to 11 PM PDT Tuesday for PZZ273.
&&

$$

www.weather.gov/portland

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