692
FXUS66 KPQR 091015
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
315 AM PDT Mon Jun 9 2025

.SYNOPSIS...High pressure aloft will begin to weaken today, but
not before supporting one final day of hazardous heat across
inland areas while the coast begins to cool. Increasing onshore
flow will see a cooling trend continue through the workweek.

&&

.SHORT TERM...Now through Tuesday Night...Upper-level ridging
has peaked in amplitude overhead as the ridge axis has shifted
east of the Cascades and will continue to track toward the
Rockies as the ridge deamplifies through this week. Along the
coast, a cooling trend will begin today due to strengthening
onshore flow, while inland areas are in for one additional day
of heat. Conditions will begin very mild this morning, with
temperatures in the upper 50s to mid 60s challenging daily
record-high minimums across the region. Mid-level air remains
very warm overhead, with 850-hPa temperatures of 19-21C
continuing through today, values some 2-3 std deviations above
normal for this time of year. Deep mixing and abundant sunshine
will again realize hot conditions at the surface, and there
remains high confidence in another day of afternoon highs in the
low to mid 90s across the Willamette, Lower Columbia/Cowlitz,
and Hood River Valleys, with a 60-80% chance of highs in excess
of 95F from Portland/Vancouver east to Hood River and south to
Eugene/Springfield and Cottage Grove. The hottest temperatures
are again likely from the Portland/Vancouver Metro east through
the Columbia River Gorge to Hood River. Daily record highs along
the I-5 corridor may again be in jeopardy.

This combination of record-challenging morning and afternoon
temperatures will continue to present higher risks of heat
illnesses, and Heat Advisories remain in effect across inland
low-elevation areas through 10 PM this evening. Those sensitive
to heat, and especially those without effective cooling and/or
adequate hydration, may feel impacts from this level of heat.
Those seeking relief in area lakes and rivers should also be
aware that water temperatures are still very cold and
hypothermia can occur despite the hot air temperatures.

The cooling trend begins in earnest across the region tonight
into Tuesday as upper-level ridging continues to break down and
exit eastward, allowing temperatures to begin falling closer to
seasonal norms. Overnight lows in the 40s and 50s will provide
relief from the daytime heat, and highs will likely reach only
into the 60s along the coast, 70s at higher elevations, and 80s
in interior valleys. There is still a 25-50% chance that those
along the I-5 & I-84 corridors will see highs reach 90 degrees
one more time before the heat truly relents, however, and daily
record highs in the low 90s inland will have a 10-25% chance of
being surpassed. -Picard


.LONG TERM...Wednesday through Sunday...Ensemble guidance
remains in good agreement that upper-level ridging will be
replaced by weak troughing in the Pacific Northwest through the
latter half of the week. Increased onshore flow will continue to
see temperatures cool toward seasonal norms, with increasing
confidence in highs in the 70s along I-5 & I-84 by Friday and
Saturday while coastal areas see highs in the 50s to 60s. There
is growing consensus that a closed upper low will track to the
southeast from south-central Alaska toward the Haida Gwaii,
while repeated shortwave impulses on its southern flank may
bring chances for rainfall to the region by Friday or the
weekend. At this lead time, global ensemble members suggest only
very light potential rainfall amounts with any disturbance that
does affect the region. -Picard


&&

.AVIATION...High pressure persist throughout the airspace,
gradually turning zonal after 06Z Tuesday. Expect a continuance
of clear skies and VFR conditions for inland terminals. The
coast will differ, with IFR/LIFR conditions through most of the
TAF period. There is higher confidence of these conditions
developing at KONP rather than KAST, as northerly winds have
been keeping KAST clear. Nonetheless, KAST has a 10-20% chance
of LIFR conditions and a 30-40% chance of IFR conditions before
18Z Monday and after 03Z Tuesday. As for KONP, there is a 70-90%
chance of LIFR conditions before 16Z Monday and a 30-40% chance
of LIFR conditions after 03Z Tuesday. Looking at 18Z Monday to
00Z Tuesday, coastal terminals have a 70-90% chance of briefly
improving to VFR between these times.

Otherwise, expect light and variable coastal winds becoming
northwesterly around 8-11 kt from 18Z Monday to 03Z Tuesday.
Winds will be breeziest at KONP Monday afternoon where gusts up
to 20 kt are expected. Inland, winds keep northwesterly and
under 10 kt.

This afternoon will feature hot temperatures in the mid to upper
90s, which could result in lower air density conditions at the
inland terminals.

PDX AND APPROACHES...VFR under clear skies through the period.
Light northwesterly winds around 5 kt overnight, becoming 7-9 kt
around 22Z Monday to 04Z Tuesday. ~Hall

&&

.MARINE...Surface high pressure centered well offshore will
maintain a northerly wind regime over the coastal waters through
this week. Small Craft Advisories continue as seas remain around
6-8 ft due to a building mid period swell from the northwest.
Northerly winds also continue to strengthen a bit as the surface
pressure gradient tightens. The strongest gusts around 25 kt will
generally remain beyond 30 nm offshore. Seas will build to 8-10 ft
by Monday and persist around this range until at least Tuesday
afternoon, so Small Craft Advisories may be extended further as
we move through the week. ~Hall/CB

&&

.CLIMATE...

Daily record high temperatures

Monday, June 9:

Portland: 95 (1955)
Hillsboro:95 (1955)
McMinnville:95 (1924)
Salem: 96 (1955)
Eugene: 91 (2015)
Astoria: 87 (1924)

Tuesday, June 10:

Portland:90 (1982)
Hillsboro:91 (1932)
McMinnville:91 (1909)
Salem:93 (1940)
Eugene:90 (1940)
Astoria:83 (1889)

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Heat Advisory until 10 PM PDT this evening for ORZ108>125.
WA...Heat Advisory until 10 PM PDT this evening for WAZ204>210.
PZ...Small Craft Advisory until 6 PM PDT Tuesday for PZZ251>253-
     271>273.

&&

$$

www.weather.gov/portland

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