017
FXUS66 KPQR 060924
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
224 AM PDT Mon Oct 6 2025

.SYNOPSIS...Conditions will remain dry with clear skies and
warm afternoon temperatures through Tuesday. Offshore flow with
breezy winds continue through Tuesday morning. Frost is likely
in the Upper Hood River Valley from Odell to Parkdale between
this morning where winds are much lighter. Temperatures trend
cooler Wednesday onward. Uncertainty remains regarding when rain
showers will return to the area, though most guidance holds off
on precipitation until Friday night or Saturday.

&&

.DISCUSSION...Monday through Sunday...Satellite imagery early
Monday morning shows clear skies across NW Oregon and SW
Washington as upper level high pressure builds over the region.
Observations at 2 AM PST show temperatures in the Upper Hood
River Valley have already fallen into the 30s, and are around
5-8 degrees cooler than 24 hours previous. A Frost Advisory
remains in effect for this area until 9 AM, including Parkdale
and Odell, as temperatures will continue falling into the low to
mid 30s.

The surface thermal trough has formed a bit farther east of the
coast than previously expected, so current pressure gradients
are not as tight as expected at this point. However, guidance
continues to indicate that the thermal trough will peak over the
coast with pressure gradients tightening through the early
morning hours. Gradient trends follow this guidance as the PDX-
DLS gradient observations have increased from -1.4 to -1.9 mb
from 11 PM to 1 AM. Offshore winds will increase as the pressure
gradients increase. Expecting peak gusts across the Cascades to
be mainly 25-30 mph with a few gusts up to 35 mph in wind prone
areas and up to 35-40 mph in the western Columbia River Gorge.
Gusts across the valley will be a bit weaker than yesterday,
mainly up to 20 mph with few up to 25 mph. Expecting more gusts
over the Coast Range today up to 20-25 mph, as well. Winds will
begin decreasing this evening for everywhere except for the
Cascades, where winds won`t decrease until early Tuesday morning
as the thermal trough breaks down. Relative humidities dropped
into the 20s to 30s inland yesterday and are expected to be even
lower today and Tuesday. However, fuels are not susceptible to
rapid fire spread after recent rains. Even then, those who will
be burning today should still use caution due to the breezy
winds.

Daytime temperatures remain warm for October through Tuesday as
offshore winds continue. Inland valleys will see high
temperatures around 75-78 degrees, possibly up to 80 degrees in
the southern Willamette Valley. Even along the coast,
temperatures could reach the low 70s today due to the offshore
flow limiting the sea breeze. As offshore winds decrease
tomorrow, coastal locations may not be as warm, but could still
peak in the upper 60s to right around 70 degrees.

Ensemble guidance is coming into better agreement on the general
upper level pattern for Wednesday into the weekend. 00z LREF
cluster analysis, which includes all members of the GFS, Euro,
and Canadian ensembles, now indicates an upper level trough will
deepen from the western Canadian coast into the eastern Pacific,
just off the PacNW coast, late Tuesday into Wednesday, forming
a closed low. The closed low will continue deepening to off of
the northern California coast Friday, then slowly move inland
sometime late Friday or Saturday. This will bring much cooler
temperatures to the region Wednesday through the weekend.
Daytime temperatures are forecast to be around 10-15 degrees
cooler Wednesday than Tuesday with inland valleys in the mid
60s and the coast and higher elevations in the 50s.

Rain chances return with this low, as well, though uncertainty
continues in exactly when rain chances begin. This is due to
some continued uncertainty in how close to the coast the low
will move as it deepens. There`s around a 15-35% chance of rain
returning late Wednesday into Thursday, with higher chances over
the coast and terrain. Chances increase to around 40-60% on
Friday. The majority of ensembles are in agreement of rain
returning Saturday with chances increasing to 70-85% for
Saturday.

By Sunday, there`s more uncertainty in the track of the upper
low. About half of the ensemble members suggest a faster
movement, with the low moved mainly east of the Cascades on
Sunday, bringing dryer conditions to the region. The other half
indicate the trough will continue into Sunday, bringing
additional rain chances to the region. Overall, not expecting a
significant amount of rain through the weekend with this low
pressure system. General QPF is around 0.5-0.75 inch for the
interior lowlands 0.75-1 inch along the coast, and 0.75-1.3 inch
for the Cascades. NBM indicates a 60-70% chance of at least 0.5
inch for the interior lowlands and a 50-70% chance of 1 inch for
the coast and Cascades through Sunday. -03





&&

.AVIATION...Clear skies and VFR conditions throughout the
airspace prevail through the TAF period as high pressure builds
into the region. Winds will vary from northerly to easterly for
each terminal. For coastal terminals, expect mostly northeasterly
winds under 10 kt through the TAF period, with winds possibly up
to 12 kt between 18-23Z Monday. As for inland along the Columbia
River, northerly winds will be prominent until 15-18Z Monday,
then shift more easterly thereafter. KTTD will be the exception,
with easterly winds through the entire period. Terminals in the
central and southern Willamette Valley will remain northerly
through the TAF period. Inland winds will remain under 10 kt
through most of the TAF period, with winds around 8-12 kt and
gusts up to 20-25 kt possible between 18-23Z Monday.

KPDX AND APPROACHES...VFR with clear skies through the TAF period.
Northerly winds under 10 kt through 16-18Z Monday. Easterly winds
around 8-12 kt with gusts up to 20-25 kt possible between 18-23Z
Monday. -12/03

&&

.MARINE...High pressure and tightening pressure gradients due to
a thermal trough developing along the coast will continue
northerly winds across the waters through Wednesday. Winds will
weaken to less than 20 kts Monday morning. Winds will increase
again in the afternoon and evening hours, but gusts over 21 kts
will be mainly for locations 40-60 NM west of the coast.
Confidence for widespread gusts over 21 kt across the outer water
zones was not high enough to warrant a Small Craft Advisory for
Monday afternoon/evening. However, by Tuesday afternoon, winds
expected to increase again with a 70-90% chance of Small Craft
winds through early Wednesday morning. Seas around 4-6 ft at
11-12 sec Monday into Tuesday. -10/03

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Frost Advisory until 9 AM PDT this morning for ORZ121.

WA...None.

PZ...Small Craft Advisory until 8 AM PDT this morning for PZZ272-
     273.

&&

$$

www.weather.gov/portland

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