081
FXUS66 KPQR 062145
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
244 PM PDT Sun Sep 6 2026

.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 18Z Monday...A low pressure system overhead
will shift east of the Cascades after 00z Monday with increasing
northerly flow aloft today. Steady rain across the Willamette
Valley will gradually dissipate becoming more showery through this
afternoon. Areas within the heaviest rainfall are experiencing
reduced VIS and lowered CIGs to low MVFR and brief periods of IFR.
Expect conditions to generally improve to widespread VFR by 20-21z
today. Confidence is high that marine stratus will push onto the
coast by 02-03z with low MVFR to IFR CIGs likely. There are also
increasing chances for MVFR stratus to develop after 12-14z Monday
across inland terminals. Expect generally light and variable winds
at most terminals through tomorrow morning.

KPDX AND APPROACHES...Predominately VFR conditions expected
through at least 12z Monday. Light rain expected to become more
scattered this afternoon as showers gradually dissipate through
04z Monday. There is around a 40-50% chance for MVFR stratus to
develop between 12-18z Monday. Light and variable winds expected
through the period, except SW winds to around 6 kt possible this
afternoon. /DH

&&

.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). 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. /DH

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...None.

&&

$$

www.weather.gov/portland

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