719
FXUS66 KPQR 262206
AFDPQR

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

.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 and marine stratus over the next 24
hours. Coastal terminals will generally be MVFR but some areas,
like KONP, will experience IFR conditions. There is a 30% chance
of IFR CIGs along the coast. Satellite shows low-end VFR CIGs with
multi-layer cloud deck inland. Overnight, the lower level clouds
will become more dense. Near the Cascades, east of KSLE, will see
a 40-50% chance of MVFR CIGs. Trended towards a "high-end" MVFR
deck, though it is nearly as probable that VFR conditions will
prevail.

Westerly winds within the Columbia River Gorge will amplify not
only this afternoon, but also after 20Z Friday. This will mainly
impact terminals like K4S2.

PDX AND APPROACHES...Mixture of MVFR and VFR conditions with a 75%
chance of VFR CIGs through the next several hours. MVFR stratus
will reform overnight just to the east of the airport and
therefore, cannot rule out back building of the stratus onto the
runways and impacting easterly approaches. Breaking out of clouds
will occur once again after 18Z Friday. -Muessle

&&

.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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