833
FXUS66 KPQR 261059
AFDPQR

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

.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 12Z Sunday...Generally VFR conditions
persist through the forecast period as high clouds overhead AOA
20-25kft slowly move off to the east early this morning.
However, given the clearing of this cloud layer near sunrise,
recent rainfall, and light winds we`ll have to keep an eye out
for patchy fog/low stratus through 16-17z. Probabilities for
IFR or lower conditions sit around 15-25% for inland terminals,
highest in the central and southern Willamette Valley. High
confidence in widespread VFR CIGs/VIS 17-18z onward. Light winds
become north around 10-15 kt at the coast and across the
central and southern Willamette Valley after 19-20z today.

KPDX AND APPROACHES...VFR conditions are expected through the TAF
period today. That said, there is a 15-23% chance for MVFR/IFR
conditions at any point between 13-17z this morning. Light winds
become northwest around 6-12 kt this afternoon. -99

&&

.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). That said, Small Craft Advisories
remain in effect early this morning for most of the coastal waters
as steep seas of 8 to 9ft at 8 seconds have been slow to
moderate. After a break midday another round of Small Craft
Advisories are in effect beginning Saturday 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 shift 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 until 8 AM PDT this morning for PZZ210-
     251-252-271>273.
     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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