Oregon City, Oregon 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

604
FXUS66 KPQR 121803
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
1103 AM PDT Tue Aug 12 2025

.UPDATED AVIATION DISCUSSION.

&&

.SYNOPSIS...Hot temperatures continue today, with afternoon
highs forecast near 100 degrees across interior valleys. Mild
conditions continue along the coast. Stronger onshore flow
returns Wednesday to Thursday, cooling temperatures by 10 to 15
degrees. Friday into the weekend, a low pressure system in the
northeast Pacific will return widespread rain across the region
and much cooler temperatures.

&&

.SHORT TERM...Now through Thursday Night...The high pressure
ridge over the northeast Pacific remains in place today,
bringing one more day of hot temperatures with sunny skies
across northwest Oregon and southwest Washington. The coast
remains mild with onshore flow, with some locations receiving
morning marine stratus and/or fog. Extreme Heat Warnings and
Heat Advisories remain in effect through 10 PM this evening,
with the hottest temperatures expected across the Willamette
Valley, southwest WA lowlands, Columbia River Gorge, and Upper
Hood River Valley. Temperatures are struggling to fall below 70
degrees this morning around the Portland/Vancouver Metro Area
and Columbia River Gorge, which is limiting the morning relief
from yesterday`s heat. High temperatures within areas of the
Extreme Heat Warning are forecast between 98 to 102 degrees. Be
sure to stay hydrated, take plenty of breaks from the heat, and
check on those most sensitive to heat. Fortunately, overnight
temperatures will be cooler tonight as onshore flow begins to
strengthen, bringing more relief from today`s heat heading into
tomorrow.

Wednesday marks the beginning of a notable cooldown as high
pressure breaks down due to an upper-level trough moving
southward from western Canada. This will strengthen onshore
flow, turning winds more west-northwesterly and bringing a
deeper marine layer along the coast. While daytime temperatures
will drop about 10-15 degrees, it will still be warm with
afternoon highs forecast in the mid to upper 80s across interior
valleys. The most noticeable cooldown will be felt the further
north you go. HeatRisk will fall back down to the "Minor"
category across the entire area, and overnight lows will
continue to drop to more comfortable temps - upper 50s to low
60s.

On Thursday, the aforementioned trough will progress eastward,
however, another upper level trough originating from the Gulf
of Alaska will begin to trek southward into the Pacific
Northwest. This will maintain robust onshore flow with winds
turning more westerly. Thursday afternoon highs are forecast
near or slightly below seasonal norms - upper 70s to low 80s
across interior valleys and 60s along the coast. Marine clouds
may push into the Willamette Valley Thursday morning, but
clearing is uncertain as the trough will begin to filter in more
mid to high level clouds across the region by the afternoon. In
addition, rain chances return to the area by Thursday evening.
Most locations remain dry on Thursday, however, the north Oregon
and south Washington coasts may end the day with around
0.05-0.10" of rain (20-30% chance of exceeding 0.10"). More
details on the upcoming rain below!          -Alviz


.LONG TERM...Friday through Monday...Rain chances increase
early Friday into Saturday as ensemble guidance is in agreement
that the upper level trough from the Gulf of Alaska will
continue to progress further south, centering just offshore of
British Columbia. The warm front associated with this system
will bring steady rain on Friday with the trailing cold front
pushing through Friday night into Saturday morning. This frontal
passage will shift winds more southerly to southwesterly, and
last through Saturday. Temperatures Friday and Saturday will
also cool below-normal, with afternoon highs forecast in the low
to mid 70s across interior valleys.

There is high confidence that that we`ll see widespread
measurable rain (>0.01") across the region, however, there is
still a lot of uncertainty among the models with exactly how
much rain we will receive in the end. The 25th to 75th
percentile interquartile range for rain at KPDX on Friday is
0.15" to 1.29", with the 10th percentile (driest scenario) being
completely dry and the 90th percentile (wettest scenario) being
1.66". It will depend on how far south the trough decides to
fall, and right now it looks like the GFS ensemble has the most
members bringing in the wetter outcomes. For now, chances for
0.50" of rain or greater from 5 AM Friday to 5 AM Sunday are
around 50-70% from Lincoln City and Salem northward, and 30-50%
south of Lincoln City and Salem as you head towards Lane County.

While this kind of pattern is not the most favorable for
thunderstorms, it can`t be completely ruled out. Once the cold
front pushes through on Saturday, will see lingering showers and
potential for some cloud breaks. This could increase afternoon
instability and thus, lead to thunderstorm development. However,
confidence in thunderstorms is low at this time and remain
around a 10-20% chance along the crest of the Cascades Saturday
afternoon. Sunday to Monday, the trough will weaken and progress
eastward, returning drier conditions and warmer temperatures.
                                                     -Alviz

&&

.AVIATION...Late this morning satellite imagery and terminal
observations depict marine fog/stratus receding along the
coastline with conditions at coastal terminal quickly trending
back to VFR 18-20z. Willamette Valley terminals will maintain VFR
conditions with clear skies through the entire TAF period.
However, confidence is high in the return of IFR/LIFR CIGs/VIS
this evening along the coast with degraded conditions beginning
02-08z. Most locations maintain westerly to northwesterly winds
around 5-10 kt today.

Important note: With hot temperatures forecast today, be aware of
high density altitude concerns (and reduced aircraft performance
as a result).

PDX AND APPROACHES...VFR with clear skies through the TAF period.
Northwesterly winds under 10 kt. -Schuldt

&&

.MARINE...Dense fog across the inner waters (from shore to 10
NM out) may reduce visibilities to 1 NM or less at times;
therefore, a Dense Fog Advisory is in effect for the inner
waters and Columbia River Bar through 1100 Tuesday. Fog should
dissipate by late morning as daytime heating progresses.
Otherwise, high pressure will maintain northerly winds across
the coastal waters today and Wednesday. These winds will be
breeziest this afternoon and over the outer waters beyond 10 NM,
with gusts to 20-25 kt. Expect seas around 7-9 ft at 9-10
seconds through Wednesday with a northwesterly swell. Small
Craft Advisories remain in effect across the outer waters and
has been extended through 1100 Wednesday, mainly for choppy
seas.

A pattern change arrives Thursday as a low pressure system in the
northeast Pacific shifts winds more southwesterly. We`ll need to
monitor southerly winds Friday to Saturday as guidance now
suggests a 20-50% chance for Small Craft conditions during the
frontal passage, with the highest chances across the inner waters
north of Cape Foulweather and Columbia River Bar.      -Alviz

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Heat Advisory until 10 PM PDT this evening for ORZ104-105-108.
     Extreme Heat Warning until 10 PM PDT this evening for
     ORZ109>125.
WA...Heat Advisory until 10 PM PDT this evening for WAZ202-204-208.
     Extreme Heat Warning until 10 PM PDT this evening for
     WAZ205>207-209-210.
PZ...Small Craft Advisory until 11 AM PDT Wednesday for PZZ271>273.
&&

$$

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