070
FXUS66 KPQR 080858
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
158 AM PDT Tue Sep 8 2026

.SYNOPSIS...Drier and warmer conditions persist through
Thursday with temperatures gradually warming and peaking on
Wednesday with the development of low-level offshore flow.
Cooler temperatures Friday into Saturday with increasing chances
for rain. The forecast becomes more uncertain Sunday into
Monday, with the potential for weather conditions to range
anywhere from cool and showery to warm and dry depending on the
evolution of the large scale weather pattern.

&&

.DISCUSSION...Tuesday morning through Monday...Satellite imagery
early Tuesday morning shows mostly clear skies across NW OR and
SW WA with a few pockets of developing stratus and fog in
sheltered valleys due to light winds and saturated soils from
recent rains. This stratus or fog should dissipate by late
morning with sunny skies and warming temperatures expected
across the area today. Ensemble guidance is in good agreement
that upper heights over the PacNW will raise today into
Wednesday as the upper low from previous days continues moving
east into the Northern Plains and high pressure over the desert
SW slowly spreads into the Western US. At the surface, a thermal
trough will push north from CA, bringing weak offshore flow
(east winds over terrain and the coast and north winds for the
interior lowlands). These features will bring continued dry
weather as well as a brief warming trend into Wednesday. Daytime
temperatures are expected to rise into the upper 70s to around
80 degrees for the interior lowlands today and low to mid 80s on
Wednesday. Coastal communities will also be warmer due to the
offshore flow, in the upper 60s to low 70s today and low to mid
70s on Wednesday. There`s around a 10-15% chance that coastal
cities off the immediate coast could reach 80 degrees on
Wednesday if increased east winds continue into Wednesday
afternoon.

Ensemble members have come into much better agreement on the
weather pattern for Thursday into Saturday than 24 hours ago. On
Thursday, a weak trough begins pushing south into the PacNW,
lowering heights and pushing the surface thermal trough south.
This will allow temperatures to lower back to near to slightly
below normal for early September (upper 70s for the interior
lowlands), though dry conditions will continue.

On Friday, ensemble members indicate another trough develops
over the western Canadian border and drops south into the PacNW
Friday into Saturday. Uncertainty still exists on the exact
track and timing of this low with 80% of members suggesting the
trough will deepen along the coast while the other 20% suggest
the trough will deepen a little more inland over WA and OR. Then,
60-70% of the members indicate the trough will move east of the
Cascades by Sunday morning where the other 30-40% suggest the
trough will linger longer into the day on Sunday with around
10-15% keeping the trough over the PacNW into Monday. Even with
the uncertainty, nearly all members indicate rain will return
to the area sometime Friday night into Sunday, though the exact
track will determine how much rain and where it will fall.
Friday night into Saturday has the highest confidence with the
latest NBM deterministic forecast now indicating a 40-50%
chance of rain late Friday into Saturday evening across the
entire forecast area. Part of the reason for the lower
probabilities is likely more to do with the timing of when the
trough will push through the area as opposed to whether it will
actually rain or not. There`s a 65-75% chance that any location
will receive at least 0.01 inch of rain in the 48 hours ending
at 5 AM Monday. When looking at probabilities of reaching or
exceeding 0.25 inch in the same 48 hour period, there`s a 25-40%
chance for locations west of the Cascades with a 40-55% chance
over the Cascades, including the foothills. Temperatures will
also fall fairly dramatically. Daytime temperatures will be
anywhere from 6-10 degrees cooler on Friday than Thursday with
another 2-6 degrees of cooling on Saturday. However, the
forecast temperature spread increases Saturday into Sunday as
the uncertainty in the weather pattern increases. The 10th to
90th percentile spread for the interior lowlands on Saturday is
from the low 60s to low 70s increasing to low 60s to upper 70s
on Sunday. If you have outdoor plans this weekend, keep an eye
on the forecast and plan accordingly for the rain potential.

Even with the 10-15% of ensemble members keeping the upper
trough over the region on Monday, members indicate it would
weaken and limit precipitation chances. The rest of the members
indicate dry and warmer conditions for Monday, which is
reflected in the deterministic NBM with precipitation chances
less than 10% with temperatures in the 70s for the interior
lowlands. -03

&&

.AVIATION...Through 06Z Wednesday...High pressure begins to build
across the area tonight into Tuesday morning, along with
continued northwesterly flow aloft. Expect VFR conditions through
the TAF period at inland terminals, with the exception of a 15-25%
chance of MVFR CIGs between 12-16Z Tue. As for coastal terminals,
coastal stratus or fog will bring a 30-50% chance of MVFR/IFR
conditions and 20-30% chance of LIFR conditions between 10-17Z
Tue, with the highest chances around 13-15Z Tue. Otherwise, expect
light and variable winds overnight at all terminals, then
increased northerly to northwesterly winds at most terminals by
18-20Z Tue. In general, coastal terminals will see gusts around
20-25 kt and most inland terminals around 20 kt during the
afternoon.

KPDX AND APPROACHES...Expect VFR conditions through the TAF
period, with an exception of a 15-25% chance of MVFR CIGs between
12-16Z Tue. Light and variable winds will become northwesterly
around 6-8 kt by 19-20Z Tue. ~12

&&

.MARINE...High pressure offshore will maintain predominately
northerly winds across the coastal waters through the week. A
strengthening pressure gradient on Tuesday will bring stronger
northerlies with gusts up to 25 kt as there is an 80% chance of
wind gusts exceeding 21 kt by Tuesday evening. As a result, Small
Craft Advisories remain in effect from 11 AM Tuesday to 6 AM
Wednesday for the outer coastal waters south of Cape Falcon, and
from 2 PM to 12 PM Tuesday for all other coastal waters. Breezy
north winds continue through Thursday, but should remain 20 kt or
less. Seas of around 4 ft with a dominant northwest swell at
10-12 seconds will gradually build to around 6 ft by Tuesday
evening as wind chop increases with the northerly winds. A weak
low pressure system is expected to approach the coastal waters
late Friday into Saturday. /DH/03

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 2 PM this afternoon to midnight PDT
     tonight for PZZ210-251>253-271.

     Small Craft Advisory from 11 AM this morning to 6 AM PDT
     Wednesday for PZZ272-273.

&&

$$

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