683
FXUS66 KPQR 191151 AAA
AFDPQR

Area Forecast Discussion...UPDATE
National Weather Service Portland OR
450 AM PDT Sat Sep 19 2026

Updated aviation discussion.

.SYNOPSIS...Temperatures warm up several degrees this weekend as
an upper level shortwave ridge moves over the area. Temperatures
gradually cool each day next week as an upper level trough slowly
drops southward from the Gulf of Alaska. Dry conditions are heavily
favored through Thursday afternoon with chances for rain increasing
slightly to 10-25% Thursday night into Friday.

&&

.DISCUSSION..Now through next Saturday...Satellite, surface weather,
and webcam observations from early Saturday morning depicted areas of
fog and low clouds beginning to develop over the Willamette Valley
and greater Portland/Vancouver metro. Meanwhile, the coast and Coast
Range remained overcast. High pressure has strengthened aloft this
morning compared to yesterday morning, which has allowed for a
relatively shallower marine layer compared to yesterday. As such, fog
and low clouds should scatter out and give way to sunshine earlier in
the day compared to what was observed yesterday. Locations that
observe low clouds around sunrise this morning should expect skies to
clear out sometime between 10 AM and 2 PM. If cloud cover lifts by
the early afternoon, temperatures will rebound nicely to around 75-80
degrees over inland valleys. Breaks of sun are expected at the coast
as well this afternoon, with highs around ten degrees cooler than
inland areas. Given minimal change in the overall pattern, expect
similar conditions on Sunday aside from temperatures trending a few
degrees warmer.

Model ensemble guidance is in good agreement on the synoptic scale
pattern Monday through Thursday, with all clusters depicting dry
southwest flow aloft ahead of broad troughing in the Gulf of Alaska.
With this pattern in place, confidence is high dry weather will
continue with high temperatures mainly in the low to mid 70s each day
for inland valleys and 60s at the coast. Guidance favors the warmest
temperatures early in the week with conditions becoming slightly
cooler later in the week.

Beginning Thursday night into Friday, chances for rain begin to
increase, albeit not by much. NBM 24-hr PoPs only peak between
10-25%, highest over southwest WA and near the coast. This seems
reasonable based on the latest QPF guidance from the LREF, which
shows close to 70% of ensemble guidance remaining dry while the
remaining 30% produce light rain amounts. The outcome will be
dependent on the location and amplitude of an upper level trough that
will be somewhere over the northeast Pacific late in the week. If
this trough is able to push inland, at least some rain would likely
return to the area. If this trough hangs offshore of deamplifies as
it moves towards the coast, conditions will likely remain dry. The
latter solution is currently the most likely outcome at this time.
Regardless of the outcome, there are no signs of any high impact
weather on the horizon. -23

&&

.AVIATION...Through 12Z Sunday...At 1130Z Saturday, marine
stratus remained locked in place along the coast with high-end
IFR to low-end MVFR conditions being reported at KAST and KONP.

Meanwhile, areas of fog and low clouds continue to expand across
the Willamette Valley and Portland metro. This has resulted in a
mix of flight categories inland, with surface visibilities
fluctuating between 1/2 SM and 3 SM at KHIO, KUAO, and KSLE. Dense
fog is being observed at KEUG with visibilities of 1/4 SM or
lower. Low stratus with ceilings ranging between 900-1200 feet has
developed from KTTD to KPDX. TAF sites observing fog this morning
should generally see fog lift into a low stratus deck with LIFR
to IFR ceilings later this morning, while KTTD and KPDX remain
socked in with high-end IFR to low-end MVFR ceilings.

Given how shallow the developing stratus deck is, expect skies to
clear out a bit faster today when compared to yesterday with
skies becoming mostly sunny sometime between 18-21Z Saturday. The
exact timing skies will clear out remains uncertain, hence the
range provided. That said, expect skies will clear out closer to
20-21Z rather than 18-19Z at most TAF sites.

KPDX AND APPROACHES...A stratus deck with ceilings around 1200 ft
has developed at the KPDX terminal this morning, and is expected
to linger through 19-20Z Saturday before skies clear out
thereafter and bring a return to VFR conditions. There is a 60-65%
chance ceilings will fall slightly below 1000 ft by sunrise. -23

&&

.MARINE...High pressure remains over the waters through the
weekend. Light winds will strengthen out of the north Saturday
afternoon and evening with gusts up to 15-20 kt, strongest over
the central and southern waters. Northerly winds peak in strength
Sunday afternoon and evening when there is a 50-90% chance for
maximum wind gusts of 21 kt or slightly stronger across the
waters, with the highest chances across the inner waters out to 10
NM offshore. Given wind gusts of this magnitude are not expected
to be frequent or widespread, Small Craft Advisories are not
anticipated at this time. Significant wave heights will remain
around 3 to 5 ft through the weekend, mainly driven by a
persistent northwesterly swell with a dominant wave period ranging
between 7 and 9 seconds.

Northerly winds are expected to linger Monday through Wednesday,
with wind gusts generally staying under 20 kt. A long period
west-northwesterly swell is set to arrive either Monday afternoon
or evening, pushing seas up by one or two feet. However, seas will
not be particularly steep as the dominant wave period with this
swell will be around 11-13 seconds. -23/03

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

www.weather.gov/portland

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