020
FXUS66 KPQR 091806 AAA
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
1105 AM PDT Thu Oct 9 2025

Updated Aviation discussion

.SYNOPSIS...Cooler and cloudier weather continues through early
next week. Low pressure system offshore will bring persistent
chances for rainfall beginning tonight for the coast and
Cascades and for inland locations by Thursday evening.
Precipitation chances will steadily increase through the latter
part of the week and persist through the weekend as the system
moves inland. Another low pressure system will bring continued
rain chances through at least early next week. Light snow
accumulations possible over the Cascades Saturday night into
early next week with minimal impacts expected.

&&

.DISCUSSION... Wednesday through Tuesday...The center of an
upper level closed low pressure system remains just west of the
Oregon/Washington coast early Thursday morning. A weak shortwave
along the flow is moving over western Oregon and Washington,
which will bring increasing shower chances for the Cascades,
portions of the lowlands east of I-5, and the coastal waters
this morning. Rain amounts are expected to remain limited with
these showers. This closed low will continue spinning off of the
coast through Friday, with another shortwave along the flow
expected to bring a more widespread round of showers to the
region tonight through Friday, generally spreading across the
area from the southwest to the northeast. This round of
precipitation could bring a bit more rain to the area with
around 0.15-0.35 inches in the interior lowlands and 0.3-0.75
inch to the coast, Coast Range, and Cascades.

Shower chances continue on Saturday as the closed low will
continue deepening along the coast as it begins moving inland.
Saturday morning may be on the dryer side as guidance indicates
western Oregon and Washington may be in a bit of a dry slot.
However, showers will increase later in the day as the back side
of the low begins pushing inland, with showers continuing into
Sunday. Between Saturday and Sunday, an additional 0.4-0.75
inches of rain is expected in the lowlands, 0.75-1.5 inches
along the coast and Coast Range, and 0.75-2 inches over the
Cascades.

Colder air will infiltrate the area behind this low and
associated surface front. Daytime temperatures will fall from
low to mid 60s on Thursday and Friday to the upper 50s Saturday,
and low to mid 50s on Sunday. Low temperatures will fall a bit
each day as well, from the upper 40s to low 50s for inland
valleys this morning to mid 40s by Sunday morning. Temperatures
over the Cascades and portions of the upper Hood River Valley
will fall into the 30s, and frost advisories may be needed for
some of the low lying Cascade areas and the upper Hood River
Valley. Additionally, this will lower snow levels to around
4000-5000 feet Saturday night through Sunday, increasing snow
chances to the high Cascades and a rain/snow mix to around
3500-4000 feet. Accumulations are expected to be minimal over
the passes with limited impacts, though those planning to drive
over the Cascades should be prepared for the potential of snow
covered roads.

Ensemble guidance is in good agreement that another upper level
closed low pressure system will deepen from Canada along the
Washington and Oregon coast late Sunday into Monday, with rain
and Cascade snow continuing through Monday. Some uncertainty
remains in the exact location of the low which brings
uncertainty in specific precipitation amounts, but impacts are
expected to remain limited from both rain and mountain snow. The
closed low will continue deepening Tuesday into Wednesday,
though LREF 500 mb cluster analysis indicates quite a bit of
uncertainty in the exact track of the low, producing quite a bit
of uncertainty in precipitation specifics. Ultimately, a 15-30%
chance of showers for most of the area, except for up to 45%
chance over the Cascades, continues on Tuesday and Wednesday,
though some clusters suggest dry and warmer conditions could
return by Wednesday. -03

&&

.AVIATION...Low pressure offshore will maintain southerly flow
aloft and increasing moisture through Friday. Expect predominately
VFR conditions with mid to high level clouds across the area
through at least this afternoon. A frontal band is expected to set
up near the coast from KEUG to KAST and lift NNE across the area
overnight. Conditions are likely to deteriorate during the
heavier rain showers. Along with these showers comes a 10-20%
chance of thunderstorms. Surface winds expected to generally be
variable less than 10 kt.

KPDX AND APPROACHES...VFR conditions expected to prevail through
at least 10z Friday with mid to high level clouds streaming north
across the area. Chances for rain showers increase after 10z with
around a 30% chance of CIGs falling to MVFR between 11-18z Fri.
Northwest winds expected around 5 kt becoming variable tonight.
/02

&&

.MARINE...A low pressure system formed in the waters off of the
northern Oregon coast last night and will slowly move north
through the morning hours before moving west of the waters by
midday. This low is producing thunderstorms across zones PZZ271
and PZZ272, with these thunderstorm chances continuing until the
low moves out of the waters. Additionally, winds have shifted
south to southeast and increased on the southern edge of the low
with buoy 46050 recording gusts around 21 kts since late last
night. Gusts up to 25 kts, with isolated gusts up to 30 kts, are
possible across all waters, spreading north as the low moves
north, decreasing quickly as the low moves north. A Small Craft
Advisory has been issued through 2pm PDT. Seas are expected to
linger around 5 to 7 ft through Friday.

Another surface low southwest of the waters slowly moves east
Friday into Saturday. Quite a bit of uncertainty remains on the
exact north/south location of this low on Friday, leading to
low probability (10-20%) of small craft winds (21+ kts). The low
will likely move inland on Saturday, bringing breezier northwest
winds with moderate to high probability of small craft winds. An
incoming northwest swell will likely push seas up to around 10 to
12 ft late Saturday into Sunday. Another weak low pressure system
approaches the coastal waters from the north late Sunday into
Monday. -03

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 2 PM PDT this afternoon for
     PZZ251>253-271>273.
&&

$$

www.weather.gov/portland

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