631
FXUS66 KPQR 060007
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
507 PM PDT Fri Jun 5 2026

Updated aviation discussion.

&&

.SYNOPSIS...A fairly progressive upper-level weather pattern
and a series of frontal systems with bring cooler than average
temperatures and periodic rounds of showers to the area through
Wednesday, June 10. There is also a 15-30% chance of short-lived
thunderstorms Saturday afternoon and a 10-20% chance Tuesday
afternoon. Upper level ridging will bring a warming and drying
trend June 11-15, with potential heat concerns June 12-15.

&&

.SHORT TERM...Now through Monday night...Satellite, radar, and
surface weather observations from early Friday afternoon
depicted scattered light rain showers occurring over southwest
WA, the north Oregon coast/Coast Range, and the northern
Willamette Valley/Portland metro. These showers have been too
shallow thus far for mixed-phased clouds to develop (echo tops
are generally below 10 kft), which helps explain why lightning
has not been observed with this convection. While a "one-hit-
wonder" lightning strike cannot be completely ruled out if a
cell overperforms later this afternoon, current trends suggest
showers will struggle to grow deep enough to support charge
separation/lightning. As such, there are no noteworthy impacts
occurring with these showers.

Simulated reflectivity guidance from the latest suite of CAMs
suggests these showers will become more isolated this evening into
tonight with the loss of daytime heating. However, showers will
become more widespread and relatively heavier Saturday morning and
afternoon as daytime heating resumes and synoptic scale lift ramps up
ahead of an incoming upper level trough. This trough will also bring
cooler air aloft and steepening mid-level lapse rates, supporting a
15-30% chance of thunderstorms over northwest OR and southwest WA
during the afternoon and early evening hours (mainly north of a line
extending from Florence to Eugene to Oakridge). Unlike today,
equilibrium levels with the convection on Saturday should be high
enough to support mixed-phased clouds capable of charge separation
with the strongest cells. As such, the strongest cells on Saturday
will have the potential to produce brief heavy rain, small hail,
gusty outflow winds, and a few flashes of lightning. It is worth
noting that any given shower or storm will be short-lived and
sub-severe as wind shear is limited and organized convection is not
expected. There will also be breaks in precipitation in between
showers, so those with outdoor activities should not expect an
all-day washout. Nevertheless, have your rain jackets handy as it is
unlikely any given location will stay dry the entire day. As always,
be sure to head indoors if you hear thunder and/or see a lightning
flash if possible.

In addition to showers and potential thunderstorms, increasing
onshore flow will keep westerly winds breezy through the central
Columbia Gorge and Upper Hood River Valley through Saturday with
gusts generally between 25-35 mph. That said, there is also a 5-15%
chance for isolated wind gusts of 40-45 mph any given hour through
Saturday afternoon for west-facing exposed ridgetops in these areas.
If the low shifts any further north, these winds would end up
relatively weaker.

Come Saturday evening into early Sunday morning, deterministic
and ensemble models remain in good agreement and show the upper level
trough axis shifting eastward, allowing for a weak transitory ridge
of high pressure to pass overhead. This will bring a brief period of
dry weather on Sunday during at least the morning and afternoon
hours. However, chances for steady light stratiform rain increase
late Sunday evening into Monday as the next Pacific frontal system
approaches. There is still considerable model disagreement regarding
the exact timing this system will move inland, with some guidance
showing rain beginning as early as 5-11 PM Sunday and other guidance
showing rain beginning as late as 5-11 PM Monday. All members from
the ENS/GEFS/GEPS eventually show rain arriving with this system,
despite the timing differences. -23

.LONG TERM...Tuesday through Thursday night...The long term forecast
starts out with cooler than average temperatures and occasional
showers, and ends with a warming and drying trend. Despite the model
timing differences discussed above with the arrival of a frontal
system late Sunday into Monday, ensemble guidance is in good
agreement the area will be solidly within a post-frontal showery
environment Tuesday through Wednesday under a broad upper level
trough. This will maintain cooler than average temperatures and
occasional rain, with high temperatures most likely in the 60s. It
appears showers will be most frequent on Tuesday, which is also when
the NBM suggests there is a 10-20% chance of thunderstorms during the
afternoon. NBM 48-hr probabilities for rain amounts over 0.25" peaks
between 5 AM Monday and 5 AM Wednesday, showing anywhere from a
45-75% chance for most locations in southwest WA and northwest OR,
except an 80-90% chance in the Cascades.

Conditions begin trending warmer and drier from Thursday onward.
Cluster analysis for June 11-15 for 500 mb heights generally suggest
upper level ridging will gradually develop over the region. This will
bring a prolonged stretch of dry weather, with temperatures likely
warming each day. While confidence is high temperatures will warm
significantly compared to early in the week, confidence is low
regarding exactly how warm temperatures will get. The NBM 1D Viewer
for high/low temperatures reflects this uncertainty well, showing
large model spread June 11-15. For example, the NBM 10th-90th
percentile for high temperatures June 13-15, which will likely be the
warmest days, ranges from the upper 70s to near 100 degrees for
inland valley and upper 60s to upper 80s for coastal locations.
Probabilities for a moderate HeatRisk or higher reach 25-45% for
inland valleys on June 12, 50-75% on June 13, and 65-85% on June 14.
There is a 5-20% chance for a major HeatRisk or higher on June 13 and
a 10-30% chance on June 14. Regardless of what materializes, those
planning on swimming in rivers or lakes should exercise cold water
safety and be mindful of the dangers that come with cold water. Those
who are sensitive to heat and/or have outdoor plans should keep an
eye on the forecast over the next week. -23

&&

.AVIATION...Predominately VFR conditions expected over NW
Oregon and SW Washington through Saturday afternoon. At 23z Fri,
isolated showers continue over the region, mainly limited to
the coast and terrain north of KONP. Shower activity will
increase after 08-12z Sat along the coast then spreading inland
10-12z Sat as a weather system moves east into the region. Some
showers could be heavier, causing brief periods of MVFR cigs or
vis. Additionally, there`s a 20-30% chance of thunderstorms near
and north of KSLE and KTMK and 10-20% chance elsewhere west of
the Cascades between 16z Sat to 00z Sun. Best chances will be
18-22z Sat with shower and thunderstorm chances diminishing
quickly after. Any stronger shower could produce heavy rain that
could cause brief periods of MVFR/IFR conditions, small hail,
gusty and erratic winds, and lightning.

Current winds are westerly across the region around 8-10 kts at
most TAF sites. Winds will decrease around 04-06z Sat, becoming
southerly inland and less than 6 kts. Winds increase to 8-11 kts
after 14-16z Sat as the weather system approaches, shifting
westerly again after 18-20z.

KPDX AND APPROACHES...VFR conditions through the TAF period. A few
stray light showers possible before 10z Sat, then shower activity
becomes more likely after 10-12z Sat with a 30% chance of
thunderstorms 18-22z Sat. Any stronger shower or thunderstorm
could produce heavy rain that could cause brief periods of MVFR
conditions, small hail, gusty and erratic winds, and lightning.
Westerly winds 10-12 kts shift southerly and decrease below 6 kts
after 04-06z Sat, increasing and shifting westerly again after
18-20z Sat. -03

&&

.MARINE...Overall fairly benign conditions expected through the
weekend and into next week. Expect a series of weak frontal
systems which will bring increasing winds and building seas. The
first of these frontal systems arriving today allow seas to
build into the 5-8 ft range at 10-12 seconds with westerly winds
gusting up to 20 kt. Then a more robust front arrives Saturday,
bringing more northwesterly winds by the afternoon. Winds only
increase marginally with only a 10-25% chance for Small Craft
Advisory wind gusts - highest probabilities across the outer
waters. Given the minimal confidence in Small Craft conditions,
have decided to not issue any headlines at this time. After a
lull during the day on Sunday as high pressure briefly returns,
winds increase yet again on Monday as a comparatively stronger
system moves over the waters, bringing south wind gusts up to 25
kt and seas approaching 5-8 ft. Conditions then gradually calm
into the middle the of the week as a ridge of high pressure
attempts to rebuild overhead and northwesterly winds return
while seas hold around 5-7ft around 9-11 seconds. /42-99

&&

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

$$

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