156
FXUS66 KPQR 261751
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
1051 AM PDT Sat Sep 26 2026

Updated aviation discussion.

.SYNOPSIS...A cooler and progressive westerly flow pattern
continues across the region this weekend into next week with
below normal temperatures persisting. While dry weather is
favored through Monday a weak frontal system renews chances for
rainfall Tuesday into early Wednesday, mainly near the coast
and across the north Oregon/Southwest Washington Cascades. For
the inland valleys, much of this midweek period stays dry.

&&

.SHORT TERM...Now through Monday night...Overall fairly benign
conditions are expected this weekend into early next week as
weak ridging is quickly followed by split WNW flow aloft - all
in all very little in the way of weather related impacts. Early
this morning dry weather prevails across the region with shortwave
ridging and surface high pressure beginning to build in behind
the departing system from yesterday (Friday). While temperatures
will increase slightly from the past day or two, they`ll remain
cool for mid-September (6-10 degrees below normal), with
afternoon highs generally in the upper 60s across the lowlands
this afternoon with better chances to reach into the low 70s
Sunday and Monday. Overnight temperatures also remain chilly,
particularly under mostly clear skies and light winds on Sunday
night into Monday, so additionally frost potential will need to
be monitored in the Upper Hood River Valley. Given the recent
moisture this also is decent set-up for patchy morning fog which
will reduce visibility where ever present, most likely in the
central/south Willamette Valley, coast range valleys, and
Cascade valleys.

.LONG TERM...Tuesday through Friday...The next meaningful
change in the pattern arrives on Tuesday in the form of
weakening upper-level trough and accompanying frontal boundary.
Confidence for measurable rainfall is highest along the north
Oregon Coast/Coast Range into southwest Washington where
probabilities for precipitatiion peak around 50-75% Tuesday
afternoon and evening before decreasing into Wednesday. It
remains to seen whether this weather feature is able to hold
together enough to push light rain into the Portland Metro and
Willamette Valley as only around 15-25% of the LREF ensemble
members forecast greater than trace amounts of rainfall during
this Tue/Wed time period. Then conditions trend dry again the
second half of Wednesday into Thursday morning.

Beyond this point ensembles diverge in the placement of a
potential shortwave trough or ridge feature within the larger
scale zonal flow which is anticipated to continue into the end
of the week. By late Thursday into Friday, around 20% of
Ensemble members show a weak trough moving overhead (cooler,
light rain chances), another 25% show straight zonal flow
(cooler, mostly dry) and the remaining 65% have some degree of
ridging overhead (slightly warmer and dry). Over the next few
days we should see ensembles converge towards a solution during
this late week period. -99

&&

.AVIATION...Through 18Z Sunday...Primarily VFR conditions expected
through the TAF period. At 1730z Sat, fog/low stratus is lingering
in a few inland valleys, including around KPDX north to KSPB and
KEUG. This fog is actively dissipating and should improve to VFR by
18-19z at the latest as winds increase and temperatures warm. A
broken cloud deck will spread across the region after 21z Sat,
remaining through most of the overnight hours. This is expected to
clear over the area sometime on Sunday morning.
Similar to this morning, if it clears by 10-13z Sun, patchy fog/low
stratus could quickly develop again by 12-15z with MVFR/IFR/LIFR
conditions, similar to this morning. There`s around a 15-25% chance
of this occurring at any terminal. If any fog/low stratus does
occur, expect it to dissipate by 17-19z Sun. North winds today
increase to around 10-15 kt at the coast and across the central and
southern Willamette Valley after 19-20z today, decreasing after 03-
06z Sun.

KPDX AND APPROACHES...Low stratus will improve by VFR by 19z with
VFR conditions likely to remain through the rest of the TAF period.
There`s a 10-15% chance of MVFR/IFR low fog/stratus returning after
10-12z Sun if the high cloud deck that moves in tonight dissipates
early enough Sunday morning. North to northwest winds increase to
around 8-10 kt after 21z, decreasing after 02-05z Sun. -03

&&

.MARINE...Weak high pressure progresses over the waters today
while a trough amplifies further out over the eastern Pacific
allowing for the return of somewhat calmer conditions, especially
compared to yesterday (Friday). However, another round of Small
Craft Advisories are in effect beginning this afternoon/evening
through early Sunday morning mainly due to northerly wind gusts up
to 20-25 kt. Northerly winds hold in place through the weekend
before another weak front shifts winds more southwesterly Monday
into Tuesday. Will also see a longer period west-northwesterly swell
of 5-8 ft at 12-14 seconds in the late Monday to Wednesday time
period, resulting in a moderate sneaker wave threat. Seas likely
stay in this 5-8ft range the remainder of the week. -99/10

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory from 5 PM this afternoon to 5 AM PDT
     Sunday for PZZ210-251-271.


     Small Craft Advisory from 2 PM this afternoon to 5 AM PDT
     Sunday for PZZ252-253-272-273.
&&

$$

www.weather.gov/portland

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