Lake Oswego, Oregon 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

131
FXUS66 KPQR 270400
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
900 PM PDT Thu Jun 26 2025

Updated aviation discussion.

.SYNOPSIS...After one more day sitting in an onshore flow
pattern with patchy drizzle (mainly near the coast) and near to
slight below normal temperatures, a rapid warming trend takes
hold over the weekend into early next week. Confidence is high
inland temperatures approach or exceeding 90 degrees in many
locations on both Sunday and Monday. We`re also keeping an eye
on the growing possibility (20-40%) for Cascade thunderstorms
early next week as well. At least high temperatures trend
cooler (low to mid 80s) by the middle of next week.

&&

.SHORT TERM...Now through Saturday Night...Current radar and
satellite imagery depicts increasing cloud cover and shower
activity near the coast in response to a weak upper-level
shortwave trough beginning to move inland. This features likely
increase light shower activity across the north Oregon
Coast/Coast range through the Washington Coast and Willapa Hills
into the early evening hours while maintaining broad onshore
flow through tonight. Can`t rule out a light shower
Longview/Kelso northward or in the south Washington Cascade
foothills too, but the bulk of the activity inland should stay
to our north.

Overall guidance shows little day to day change in conditions for
Friday albeit with any lingering light rain showers/drizzle
holding more confined to southwest Washington excluding the
lowlands south of Longview/kelso. Cloud cover has the potential
to scatter out a bit more during the afternoon hours,
especially in the central and southern Willamette Valley,
allowing high temperatures to increase a few degrees into the
mid 70s where this clearing takes place. Through Friday onshore
flow will also maintain breezy west winds through the central
Columbia River Gorge each afternoon as winds gust to 25-35 mph
in some spots around Hood River.

Come Saturday upper-level heights begin to rise across the
area as a ridge of high pressure slowly starts to amplify over
the Pacific Northwest favoring dry conditions. At the same time,
both deterministic and ensemble models depict a cutoff low
developing over the California coast - this will come into play
regarding T-storms chances early next week (see Long Term
discussion). The persistent morning cloud cover which has kept
a damper on temperatures the last couple of days will be less
prevalent thanks in-part to a developing offshore component in
winds just above the surface. As a response, high temperatures
jump into the upper 70s to low 80s across the inland valleys -
roughly 2 to 5 degrees above normal for late June. Expect
temperatures to keep climbing the second half of the weekend
too. -Schuldt

.LONG TERM...Sunday through Wednesday... Warmer weather finally
takes hold on Sunday with offshore flow in place across the
region at 850mb and a near surface thermal trough overhead as
well. Temperatures still look to peak during this early next
week period (Sunday and Monday) as the ridge continues to
amplify, with the NBM now depicting a 40-70% chance to meet or
exceed 90 degrees in the Willamette Valley on Sunday followed
by a 75-90% chance on Monday. Probs to reach 95 degrees continue
to sit closer to 15-35% in most locations in the Willamette
Valley, representing more of a reasonable worst case scenario
for heat on Monday. Temperatures look to slowly decrease
somewhat beyond Monday, but will still remain well above normal
as guidance keeps highs in the 80s for much of the rest of the
week, showing around a 30-45% to reach as high as 90 degrees for
Tuesday through Thursday - higher model uncertainty resolving
the upper-level pattern by the middle of next week.

The other forecast concern in the long term will be the
potential for thunderstorms along the Cascades during the first
half of next week (highest relative threat on Monday) which
will largely be dependent upon the evolution of the
aforementioned cutoff low near the California coast. This will
have the potential to draw monsoonal mid level moisture
northward into our area in southeast flow aloft, which is often
challenging for the NBM to resolve. A farther north position of
the low will generally be more favorable for thunderstorms to
reach into the northern Oregon Cascades and south Washington
Cascades. Confidence is decent (50-60%) for activity in at
least the eastern Lane County Cascades southward. One
interesting facet worth highlighting is most current model
solutions shows a slight easterly component to the southerly
flow between 700-500mb which would promote a longer residence
time for activity over the Cascades should it develop. For now,
will maintain a 15-24% chance of thunderstorms along parts of
the Cascades both Monday and Tuesday afternoon, but will need to
keep a very close eye on how this pattern evolves in the coming
days. -Schuldt/CB


&&

.AVIATION...Onshore flow continues for the next 24 hours. As of
04z Fri, most locations have lifted to VFR except for isolated
locations along the coast. Marine stratus deck is once again
expected to form along the coast by 06z Fri with very high
confidence in MVFR ceilings continuing through 18-20z Fri. There`s
also a 30% chance of IFR ceilings at times. Forecast for inland
locations is a little tricker as a mid-level overcast cloud deck has
settled over the area, which could limit the ability of MVFR
ceilings to develop. Guidance indicates a higher (60-80%) chance of
the cloud deck lowering to MVFR along the eastern Willamette Valley
and backbuilding to the west into the Valley. This would include
terminals such as KPDX and KTTD. For terminals along and west of
Interstate 5, there`s closer to a 50% chance of whether MVFR
ceilings will backbuild that far west. However, based on pattern
recognition, have decided to include MVFR ceilings in all inland
TAFS beginning around 10-12z Fri. Conditions should return to VFR by
18-21z Fri. Winds remain light, generally less than 10 kts, except
for in the Columbia Gorge east of KTTD where westerly winds will
amplify after 18z Fri with gusts up to 25 kts.

PDX AND APPROACHES...VFR conditions expected to become MVFR around
10-12z Fri as stratus builds in from the east, with conditions
improving by 18-20z Fri. Northwest winds 6 kts or less. -HEC

&&

.MARINE...Weak perturbations will move through the onshore flow
through the Saturday before high pressure begins to build on
Sunday. Westerly winds of 5-10 kt with gusts up to 20 kt expected
through Friday, before sifting to the north at 15-20 kt with
gusts up to 25 kt Saturday night. The waters south of Tillamook
have a 70% chance of gusts up to 30 kt, and elsewhere around a 40%
chance. Ultimately, gusts will be dependent on the strength of a
ridge and thermal trough that are beginning to develop Sunday.
Seas during this time will remain generally unchanged at 5-7 ft at
9 seconds except where wind waves are higher.

Moving into Sunday and Monday, weather will become more dynamic as
temperatures rise considerably, and a low moves over northern
California. This pattern is consistent with increasing
thunderstorm chances. While this will mostly impact areas inland,
cannot rule out a strike or two on Monday evening. -Muessle

&&

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

$$

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