790
FXUS66 KPQR 170500 AAA
AFDPQR

Area Forecast Discussion...UPDATE
National Weather Service Portland OR
1000 PM PDT Wed Sep 16 2026

Updated Aviation discussion

.SYNOPSIS...Warmer and drier weather conditions through
tomorrow as weak offshore flow persists. Onshore flow returns
late tomorrow, while dry conditions are expected to persist
through the weekend. A cooler pattern may develop early next
week as troughing approaches from the Gulf of Alaska.

&&

.DISCUSSION...Now through Tuesday...Warmer conditions expected
through Thursday as upper level ridging over the northeast
Pacific slowly shifts eastward and a closed upper level low
shifts southward over northern California. A surface thermal
trough will support offshore flow across the Cascades and into
the Foothills and western Columbia River Gorge while north to
northeast winds will be expected elsewhere. Gusts up to 20 mph
will remain possible across the Willamette Valley and up to 25
mph through the Columbia River Gorge through the evening.

Dry conditions are expected for most of the area as the upper low
shifts southward. The only notable chance for a stray shower is over
far southeastern Lane County, closest to the upper low and where the
best moisture and lift will be relatively. Satellite and radar
observations indicate some broken cloud cover and light radar
returns as of 130 PM but unlikely anything is making it to the
ground. Chances for precipitation peak late this evening around
10- 20% along the southeastern border of Lane and Douglas
county.

Thursday is still expected to be the warmest day this week with
highs peaking in the low to mid 80s across the interior lowlands.
Weak offshore flow is expected during the morning but will gradually
shift onshore by the afternoon as the thermal trough dissipates.
Probabilities for temperatures to peak at 85 or above range
from 20- 60% north of Corvallis to the Portland metro with the
greatest chances across the Tualatin Vally. Areas south of
Corvalis are expected to top out in the low 80s. Highs in the
upper 60s to mid 70s are expected along the coast and in the
higher terrain of the coast range and Cascades. The upper low
over northern California is expected to begin shifting northeast
toward the Great Basin as ridging moves in from the west which
will bring a slight increase in moisture across the Lane and
Linn county Cascades. This will support a 20-40% chance for
showers and a 10% chance for a stray thunderstorm.

Conditions are expected to remain dry Friday but there is a bit more
spread among the ensemble models regarding high temperatures as
the upper level pattern begins to shift. Friday morning likely
begins with marine stratus along the coast and interior lowlands
as onshore flow persists. Highs will depend on how quickly low
clouds dissipate but also the position of the upper level low to
the east and ridge to the west. A slower, eastward progression
would keep conditions cooler in the low 70s across the interior
lowlands while a more progressive pattern would lead to slightly
warmer temperatures in the upper 70s. Better agreement heading
into the weekend with a warming trend into the upper 70s to low
80s both Saturday and Sunday. Beyond the weekend, the pattern
trends toward cooler temperatures as troughing drops southward
from the Gulf of Alaska. Details are unclear at this time in the
exact strength, location, and timing of this feature. -19

&&

.AVIATION...Through 06Z Friday...East to northeast flow aloft
continues through Thursday as an upper level low spins over
northern California. Predominately VFR conditions are expected for
inland terminals through the TAF period. At the coast, VFR is
likely through at least 00z Thu, as there is around a 10-20%
chance for fog to develop between 12-18z Thursday, potentially
lowering VIS to MVFR/IFR briefly. Higher chances for MVFR/IFR marine
stratus to return to the coast after 00z Friday as winds turn back
onshore.

KPDX AND APPROACHES...VFR conditions expected through the TAF
period with mostly clear skies. Northwest winds around 5 kt ease
overnight before increasing again to around 4-7 kt Thu afternoon.
/DH

&&

.MARINE...A strengthening thermal trough inland is increasing
pressure gradients across the coastal waters today, increasing
north winds to 15-20 kt with gusts up to 25 kt south of Cape
Falcon this afternoon, continuing overnight. Small Craft
Advisories are in effect through 11 PM Wednesday.

North winds ease Thursday then become a bit more west to southwest
for locations out about 40-50 NM from the coast late Thursday into
Friday. A persistent northwest swell around 4 to 6 ft at 7 to 8
seconds is expected to continue through at least Friday.
Northerlies strengthen again over the weekend. The waters south of
Cape Falcon have around a 50-75% chance of at least occasional
wind gusts exceeding 21 kt. The waters north of Cape Falcon have
a 30-40% chance of wind gusts exceeding 21 kt on Saturday,
increasing to 50-70% by Sunday. -03

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 11 PM PDT this evening for PZZ252-253-
     272-273.

&&

$$

www.weather.gov/portland

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