955
FXUS66 KPQR 020509 AAA
AFDPQR

Area Forecast Discussion...Updated
National Weather Service Portland OR
1009 PM PDT Tue Jul 1 2025

Updated Aviation...

.SYNOPSIS...Hot and dry weather continues today, though cooler
than Monday. Highs will still reach into the upper 80s to around
90 degrees across the interior. Isolated thunderstorms remain
possible across the Lane and Linn County Cascades this afternoon
through tonight. A cooling trend begins tomorrow, bringing more
seasonable conditions through the weekend. There are signs that
warmer temperatures may return early next week as upper level
ridging begins to rebuild.

&&

.DISCUSSION...Tuesday Afternoon through Monday...Radar imagery at
2 PM PDT on Tuesday afternoon shows scattered thunderstorms have
formed just to the south and to the east of Lane County. SPC
mesoanalysis depicts a shortwave along the low pressure system
lingering over California has brought moisture into central Oregon,
with elevated RHs at 925 mb and 850 mb. Guidance continues to
indicate that a 15-25% chance that thunderstorms could form along
the Lane and Linn County Cascade crest this afternoon and evening
due to this increased monsoonal moisture plus lift from the
shortwave. Additionally, latest runs of some CAMs indicate
isolated thunderstorms could continue through the overnight
hours for the same region, so have bumped up the thunderstorm
chances in the forecast to 15% to account for this. Main
concerns with thunderstorms are lightning, gusty winds, and
small hail.

High pressure remains over the region, though is beginning to shift
east. High temperatures will be warm though not quite as warm as
yesterday. Observations at 2 PM PDT are in the mid to upper 80s
across the Willamette Valley, which is on track to peak in the upper
80s to low 90s. Additionally, tightened pressure gradients are
producing another round of breezy north to northwest winds across
the coast, lower Columbia River, and Willamette Valley this
afternoon and evening. Expect gusts up to 25-30 mph along the coast
and 20-25 mph elsewhere into this evening.

By tonight and into Wednesday, the upper ridge continues to weaken
and shift east as troughing takes hold across the Pacific Northwest.
This will bring cooler, more stable conditions with a return to weak
onshore flow. Expect inland highs in the low 80s and coastal areas
holding in the 60s to low 70s.

This cooler pattern appears likely to persist into the holiday
weekend, with ensemble guidance in strong agreement on broad
troughing through at least Saturday. Highs in the Willamette Valley
are expected to range from the upper 70s to low 80s, which is near
to slightly above early July climatological norms. Persistent
onshore flow may also promote morning marine stratus, especially in
low lying interior areas.

By Monday of next week, ensemble guidance begins to suggest a
transition toward zonal flow, with indications of upper level
ridging re-establishing over the western US. However, ensemble
clusters begin to diverge significantly beyond Sunday, introducing
forecast uncertainty for the early part of next week. Inland
temperatures may begin to rebound, potentially returning to the
upper 80s, though confidence in the magnitude and timing of this
warming is still limited. Surface winds are expected to remain north
to northwesterly both along the coast and inland, which may help
maintain marine influence in some areas. -HEC/Hall

&&

.AVIATION...Marine stratus and fog remains entrenched along the
coast as of 05z Wed, resulting in mainly IFR conditions with some
pockets of LIFR fog around KONP. Expect these conditions to
continue through the overnight hours. Models depict some inland
intrusion up the Lower Columbia River Valley, but extent is
uncertain as guidance gives Portland area terminals a 30-40%
chance for MVFR cigs 12-16z Wed morning. Opted to leave these
sites VFR in the latest TAF package, but will have to monitor
observational trends through 12z. Marine stratus will likely be
stubborn to erode at coastal terminals through the period, with
only modest improvement to IFR/MVFR expected after 18z Wed.
Otherwise, VFR through the period at inland sites with another
round of high clouds associated with convection over the OR
Cascades. W-NW winds around 10 kt diminishing to 5-7 kt by 08z,
increasing again to around 10 kt with gusts up to 20 kt 20-23z Wed
afternoon.

PDX AND APPROACHES...VFR under broken high cirrus deck through at
least 12z Wed. A 30-40% chance for MVFR cigs 12-16z Wed as marine
stratus progresses up the Lower Columbia River Valley. Otherwise
VFR through the period. W-NW winds around 8 kt diminishing below
5 kt by 12z, then increasing to 10 kt with gusts to 20 kt after
21z Wed. /CB

&&

.MARINE...Persistent surface high pressure offshore will result in
continued north to northwesterly winds across the waters through
the week. Breeziest conditions are expected today, with gusts up
to 25 kt through this evening most likely south of Cape
Foulweather, easing to 15-18 kt or less by tomorrow. Small Craft
Advisories remain in effect through 5 PM this afternoon north of
Cape Falcon, and through 11 PM this evening from Cape Falcon south
to Florence. Choppy seas of 7-9 ft at 7-8 seconds will continue
through today, before subsiding to 3-6 ft tomorrow through the
weekend as winds weaken. -TK/Picard

&&

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

$$

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