267
FXUS66 KPQR 042213
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
312 PM PDT Sat Oct 4 2025

.SYNOPSIS...Offshore flow develops Sunday and continues through at
least Tuesday, bringing an extended period of dry and breezy
conditions with mostly clear skies and high temperatures in the 70s
across the lowlands each day. Temperatures trend relatively cooler
Wednesday onward with increasing chances for rain, however forecast
uncertainty is high mid to late week.

&&

.DISCUSSION...Saturday through Friday night...There has been very
little change to the forecast with today`s update. Models and their
ensembles remain in good agreement that upper level ridging
over the northeast Pacific will build over the Pacific Northwest
Sunday and Monday while a surface thermal trough forms along
the Oregon and southern Washington coast. This pattern will
result in the return of dry weather with warming temperatures and
strengthening offshore flow at low levels. East to northeast surface
winds may gust up to 30-40 mph at times Sunday afternoon through
early Tuesday morning, with the strongest gusts on exposed
ridgetops in the Cascades and in the western Columbia River Gorge.
Gusts up to 25 mph are expected in the Willamette Valley and
Cascade foothills, with a northerly to northeasterly wind direction.
Note northerly winds will be strongest over the central and southern
Willamette Valley, from Salem southward to Eugene-Springfield.
Although atmospheric conditions will be drying out, causing daytime
relative humidity values to fall quite significantly, the recent
rains will limit any fire weather concerns. Still, those burning
should use caution Sunday morning through Tuesday morning.

On Tuesday, the high pressure and thermal trough will begin
breaking down later in the day due to an upper level low
pressure system approaching the region, allowing winds to begin
shifting onshore again, though dry and warm conditions are
expected to continue. The forecast becomes much more uncertain
Wednesday onward as ensembles are split on how to resolve the
aforementioned upper level low.

WPC`s 12z cluster analysis for 500 mb heights (which utilizes the
GEFS/ENS/GEPS combined) still shows half of total ensemble space with
a closed low deepening right along the Washington and Oregon coast,
while the other half suggests the low will deepen just west of the
coast Wednesday through Friday. The first scenario would bring the
return of cooler temperatures and shower chances to NW Oregon and SW
Washington, whereas the later scenario would keep conditions dry and
on the warmer side. The NBM 25th percentile to 75th percentile
temperature spread for Wednesday and Thursday ranges from the low 60s
to mid 70s for daytime highs. The deterministic NBM (which our
forecast reflects) introduces a 15-35% chance of rain Wednesday
through Friday, increasing to around 45-60% chance Friday night.
-59/03

&&

.AVIATION...Satellite imagery as of early Saturday morning depicts
widespread cloud cover across northwest Oregon, with a mix of
MVFR/VFR CIGs. CIGs have been gradually lifting, so expect
predominately VFR conditions by late this afternoon/evening as
daytime heating progresses. After 03-04z Sun, marine stratus re-
develops along the coast (50-70% chance). However, winds turn more
northeasterly along the coast tonight after 08-09z Sun, favoring
dissipation of low stratus and a return to VFR conditions for KAST
and KONP. Inland, there is a 30-50% chance for MVFR CIGs after
10-12z Sun as stratus develops along the Cascade foothills and
builds westward into the Willamette Valley. Winds generally
northwesterly under 5 kt today, becoming variable overnight for
inland locations and northeasterly along the coast.

KPDX AND APPROACHES...Predominately VFR conditions through the
late evening. 15-30% chance for IFR/MVFR CIGs between 09-16z Sun.
Northwesterly winds around 5 kt or less. -10

&&

.MARINE...Surface high pressure continues to build over the
waters today with winds shifting northwesterly, remaining around
15 kt or less through the rest of the evening. Tonight into
Sunday, stronger high pressure and tightening pressure gradients
due to a thermal trough developing along the coast will shift
winds northeasterly and allow winds to increase. A Small Craft
Advisory has been issued for all waters south of Cape Falcon for a
combination of north-northeasterly wind gusts up to 25 kt and
choppy seas, beginning 8 AM for the outer waters (beyond 10 NM)
and 2 PM for the inner waters (out 10 NM). For the waters north of
Cape Falcon, chances for small craft conditions remain around 20%
or less. Winds remain northeasterly Monday, but will weaken to
less than 20 kts. Seas around 4-6 ft at 12-13 sec this evening,
with periods dropping to 8-10 sec Sunday into early next week. -10/03

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 2 PM to 11 PM PDT Sunday for PZZ252-
     253.

     Small Craft Advisory from 8 AM Sunday to 5 AM PDT Monday for
     PZZ272-273.
&&

$$

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