619
FXUS66 KPQR 112342
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
Issued by National Weather Service Medford OR
442 PM PDT Tue Aug 11 2026

...Updated aviation discussion...

.SYNOPSIS...Warm and dry conditions expected through the week
with persistent onshore flow. A stronger onshore push will bring
increasing clouds tomorrow and cooler temperatures. Mostly dry
through the weekend, but there are indications of increasing
chances for rain early next week (though chances remain low at
this time).

&&

.DISCUSSION...Satellite imagery as of late Tuesday morning
depicts mostly  sunny skies across northwest Oregon and
southwest Washington as morning stratus has dissipated. Will
continue to see some marine clouds hugging the coast through
this afternoon as we maintain onshore flow. This onshore flow
will persist throughout the week and provide near-normal
temperatures across the region for this time of year. Expect
high temperatures in the mid 80s today across interior valley
locations and 60s along the coast.

Slightly cooler conditions are forecast tomorrow (Wednesday) as
the upper level pattern shifts from zonal flow to more
troughing. Broad upper level troughing over British Columbia
this evening becomes a bit more organized as it drops south into
Washington and Oregon. This pattern typically corresponds with
a stronger push of marine stratus inland by Wednesday morning.
Like previous days, still expect the marine layer to generally
remain below 2000 ft but could see the stratus push through into
the I-5 corridor through the Coast Range gaps and Lower
Columbia River Valley. Would not be surprised for the coast to
see some drizzle Wed morning as well. With the marine layer
lingering into the late morning and early afternoon,
temperatures will be slower to warm resulting in highs reaching
into the mid to upper 70s across the southwest Washington
lowlands and Portland-Vancouver Metro Area, while temperatures
in the central and southern Willamette Valley are more likely to
warm into the low 80s. Most of the moisture associated with the
aforementioned trough is expected to remain across portions of
the northern half of Washington, keeping us dry.

There is agreement among the models and their ensembles for
later in the week with the upper level pattern trending toward
broad upper level troughing and a continuation of onshore flow.
The potential range of afternoon high temperatures from the NBM
for Thursday through Friday has generally consolidated into the
lower to mid-80s, favoring near to slightly above average
conditions for mid-August. More uncertainty into the weekend,
but ensembles are suggesting weak upper level ridging may nudge
back into the Pacific NW as low pressure deepens the upper
trough offshore. This could result in a slight warming trend,
though models suggest there is only a 15-20% chance of exceeding
90 degrees across the Willamette Valley on Sunday and Monday.
Shortwave troughs within the more southwesterly flow aloft along
with some increasing monsoonal moisture will also bring slight
chances (10-20%) for thunderstorms along the Cascade crests of
Oregon for Saturday afternoon, with the highest chances across
the Lane County Cascades.

The question then turns to the possibility of rain early next
week, but chances for measurable precipitation remains low
(15-30%) across the area next Monday. Cluster analysis of 500 mb
heights shows a wide range of the magnitudes and placements of
the upper level trough offshore, while 25% of ensembles show the
potential for any substantial rainfall (24 hour totals of
0.10-0.25") across the area.       -10/DH


&&

.AVIATION...Through 00Z Thu...A stronger onshore push will
bring a return of MVFR to LIFR conditions to all coastal
locations starting around 03-06z Wednesday. The marine stratus
is expected to infiltrate through the gaps and flows of the
coastal range as well as march down the Columbia River. Expect
these MVFR conditions to impact all inland locations starting
around 08Z-12Z Wednesday. Expect north/northwest winds to
persist through the TAF period to around 8 kts or less by 06Z
Wednesday. However, gusty north/northwest winds expected to
return towards the end of the 00Z TAF period.

KPDX AND APPROACHES...Predominately VFR with clear skies through
around 06Z Wed after which marine stratus is expected to impact
areas around the terminal. Expect MVFR conditions to persist
afterwards, with improvement towards VFR towards end of the 00Z
TAF period. North/northwest winds less than 8kts or less by 06Z
Wednesday. However, gusty north/northwest winds expected to
return towards the end of the 00Z TAF period. /42

&&

.MARINE...
High pressure offshore will continue to support
northerly winds and fairly benign conditions across the coastal
waters through the week and into the weekend. Winds from the north
to northwest with gusts less than 21 kts will continue through at
least the end of the week. Wind driven seas are expected to
remain around 3 to 6 ft through the week.       -03

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.
&&

$$

www.weather.gov/portland

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