891
FXUS66 KPQR 250439 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
938 PM PDT Thu Jul 24 2025

...Updated aviation discussion...

.SYNOPSIS...A cool down back to near normal is expected Friday
through Sunday as a large trough dips south into the PacNW.
Expect upper 70s to low 80s. Another warm up is expected early
to mid next week.

&&

.DISCUSSION...Satellite imagery shows mostly clear skies across
 the region with very sparse fair weather cumulus beginning to
pop up. The upper level pattern is a bit messy with a large
trough across western Canada and eastern Alaska and a cut-off
low over central California. In between these two features, an
elongated area of high pressure covers a good portion of the
northern Pacific from Oregon to the Aleutian Islands. This will
support highs topping out in the mid 80s inland and upper 60s
along the coast. Expect another solid marine layer to push into
the coastal areas late this evening into the overnight. HREF
guidance is suggesting another decent chance (40-70%) that
stratus will develop along the Cascade foothills and backbuild
into the Willamette Valley between 3-6 AM Friday. Any clouds
that develop inland are expected to dissipate by late Friday
morning.

Expect a modest cooldown from Friday into the weekend as the region
increasingly feels the influence of the upper level trough to the
north, bringing lowering 500 mb heights and maintaining benign
onshore flow west of the Cascades. This will equate to inland highs
closer to seasonal norms in the upper 70s to low 80s through Sunday.
Coastal areas will continue to be impacted by abundant marine
stratus through the period, with diurnal intrusions into the inland
valleys becoming increasing likely as the marine layer deepens and
onshore pressure gradients increase.

Guidance continues to suggest temperatures rebound back into the
upper 80s to low 90s Monday through Wednesday. Probabilities for
inland valleys to reach 90 degrees on Monday are modest at 10-40%
but increase significantly Tuesday and Wednesday to 50-80% for most
locations. A significant heat event is unlikely at this time given
the relatively small temperature spread heading into next week. A
deepening upper level low is also likely to set up off the British
Columbia coast, through there is a wide area where this may set up.
Depending on where it sets up, south to southeast flow could set up
across the are or at least a portion of the area, bringing monsoonal
moisture and potential for thunderstorms. Thunderstorm probability
remains below 15% for now and does not warrant inclusion in the
forecast at this time, but will have to continue to monitor going
forward depending on the ultimate position and orientation of the
trough. -Batz/CB

&&

.AVIATION...Satellite imagery as of late Thursday evening depicts
marine stratus along the coast bringing IFR/MVFR conditions to
KAST and KONP. High confidence that these conditions prevail
along the coast through Friday morning. Marine stratus should
break out and return VFR conditions to the coast by 21-23z Fri,
but there is some guidance that suggests stratus could linger
throughout the day. Will also see a stronger onshore push tonight,
bringing a 60-80% chance that MVFR stratus moves into the
Willamette Valley between 12-18z Fri (highest chances across the
Portland/Vancouver Metro Area). VFR conditions with mostly sunny
skies return to Valley terminals by 18-20z Fri. Expect generally
northerly to northwesterly winds across the region around 5-10 kt,
strongest in the afternoon.

PDX AND APPROACHES...High confidence (70-90% chance) for MVFR CIGs
across the Portland/Vancouver Metro between 13-18z Fri. Stratus
should begin clearing out as daytime heating progresses, returning
VFR conditions by 18-19z Fri. Northwesterly winds 5-10 kt. -Alviz

&&

.MARINE...Going through the end of the work week through the
weekend high pressure will maintain north to northwesterly winds
with gusts around 13-18 knots during the afternoon/evening hours
each day. Background swells don`t look particularly noteworthy so
seas likely remain around 3-6 ft each day into next week - small
Craft advisory conditions are unlikely this week. That said, it`s
worth pointing out there will be some strong ebb currents through
the Columbia River bar late this week (Friday morning) which may
lead to locally choppy seas.    -Schuldt

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

www.weather.gov/portland

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