284
FXUS66 KPQR 092036
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
136 PM PDT Sat May 9 2026

.SYNOPSIS...High pressure will maintain dry and warm conditions
through early next week. A weak shortwave trough will bring
increased cloud cover and slightly cooler temperatures tomorrow.
Temperatures rebound on Monday and Tuesday as high pressure re-
builds. Precipitation chances return on Wednesday as a trough
approaches the West Coast. Another trough from the Gulf of
Alaska will maintain precipitation chances and a trend toward
cooler temperatures by the end of next week.

&&

.DISCUSSION...Today through Friday...Satellite imagery and
surface observations as of early Saturday afternoon depicts
mostly clear skies with a few high clouds across northwest
Oregon and southwest Washington as an upper-level ridge moves
overhead. Temperatures remain seasonably warm today with
afternoon highs forecast in the upper 70s across interior
valleys and 60s along the coast. Tonight, onshore flow and high
pressure aloft will support re-development of marine stratus. We
could also see some stratus form across interior valleys early
Sunday morning as the low level atmosphere remains moist.

Tomorrow (Sunday), a weak shortwave trough will brush the
Pacific Northwest and bring mid to high level clouds over the
forecast area. Since this shortwave is tracking further north,
the bulk of the precipitation will be directed towards western
British Columbia while conditions remain dry across northwest
Oregon and southwest Washington. Because of the increased cloud
cover tomorrow, high temperatures will be a few degrees cooler
than today but remain seasonably warm across interior valleys
with afternoon highs forecast in the low 70s while coastal areas
remain in the upper 50s to low 60s.

Heading into early next week, the majority of ensemble guidance
are in agreement with upper-level ridging re-building over the
Pacific Northwest. We`ll see a return of sunny skies while dry
weather prevails. There is high confidence that temperatures
will rebound into the upper 70s to near 80 degrees by Monday
across interior valleys, however there is still some uncertainty
with how warm it will get on Tuesday. Deterministic guidance
suggests that Tuesday would be the warmest day of the week with
temperatures peaking in the low to mid 80s; however, ensemble
guidance is still uncertain with the exact timing of the trough
that follows the ridge. While the majority of ensemble members
are in agreement with the upper ridge axis being generally over
the Intermountain West, about half of the ensemble members have
the next trough tracking close to the Pacific Northwest while
the other half keep the trough further offshore in the northeast
Pacific. If the trough ends up closer to shore, we could see
increased cloud cover and slightly cooler temperatures in the
upper 70s to low 80s. If not, then temperatures could get as
warm as the upper 80s.

The next chances for precipitation return on Wednesday as the
aforementioned trough approaches the West Coast. The majority
(75%) of ensemble members show this trough tracking south of our
area, either toward the California/Oregon border or further
south into California. As a result, chances for precipitation
are currently 15-25% west of the Cascades and 25-40% across the
Cascades. In addition, southerly flow from this pattern would
bring increased instability and thus a 15-25% chance for
thunderstorms across the Linn and Lane County Cascades. The
other scenario depicted by 25% of ensemble members has the
trough swinging directly through the Pacific Northwest; in this
case, we would see increased moisture and chances for
precipitation.

There is greater uncertainty in the pattern Thursday-Friday,
however, most ensemble members are showing another trough
dipping down from the Gulf of Alaska by the end of the week.
This will maintain chances for precipitation across the area and
cool temperatures down to seasonal normals, however, the exact
track of this system, timing, and precipitation amounts are
still uncertain.        -10


&&

.AVIATION...High pressure over the area will keep most areas VFR
through the next 24 hours. The main exception to that will be
the coast as the flow turns westerly overnight and marine
stratus moves in. Thee is nearly a 70% chance of IFR CIGs near
sunrise around KAST and KONP but if winds remain northerly
longer it will be a bit more difficult for it to build in. Most
changes in the forecasts are due to winds as CIGs will generally
stay stagnant.

In the southern Willamette Valley from KSLE southward, some
models are attempting to build in lower stratus along the
Cascade foothills that may backbuild to KSLE and KEUG. However,
the probabilities are quite low so included a scattered deck.

KPDX AND APPROACHES...VFR with no concerns through the period.
                                                          -27

&&

.MARINE...Southerly winds will become more northerly this
evening as high pressure develops over the region. Overall,
will see winds of 6 to 10 kt with gusts up to 20 kt along the
coast. The highest winds are expected in zones PZZ253 and PZZ273
with less than a 10% chance of isolated gusts up 25 kt. Seas 5
to 7 ft at 10 to 12 seconds. These conditions are expected to
persist through Sunday.

There is a shift on Monday as there is the potential for a low
pressure system to move into the northeastern Pacific. At this
time, we are expecting the northerly winds to persist and
intensify on Monday with a trend towards Small Craft Advisory
level speeds through Tuesday. There is greater than an 80%
chance of gusts up to 25 kt on Monday and around a 40-50%
chance on Tuesday though would be in the morning.         -27

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...None.

&&

$$

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