746
FXUS66 KPQR 301226 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
526 AM PDT Tue Sep 30 2025

Updated Watches, Warnings and Advisories

.SYNOPSIS...A fall like weather pattern is expected to continue
through much of the week as we transition from September into
October. Expect periods of rain through at least Thursday as a
series of fronts brings unsettled weather and cooler
temperatures across the region. Breezy southerly winds expected
today, followed by rain showers and chances for thunderstorms as
a low pressure system remains offshore. Dry weather is expected
to returns for the weekend while temperatures remain seasonably
cool.

&&

.DISCUSSION...Today through Sunday...A more potent frontal
system is expected to push another round of rain onshore
starting this morning through Tuesday night as well as bringing
breezy southerly winds. Current (0230 Tuesday) Water vapor
satellite imagery shows a low pressure system centered near
48N/135W, which looks to have a center pressure around 975-980
mb. Ensemble guidance remains in very good agreement that the
surface low will remain well offshore of CONUS and near Vancouver
Island through at least Friday. By early Friday, models have
this low starting to slowly drop down towards OR/WA as well as
weaken.

Now, onto the series of fronts that this system will be sending
into the Pac NW. The warm front looks to arrive and bring
moderate rain to the area by late Tuesday morning through the
afternoon. Followed by a cold front through the evening and into
Wednesday morning, which will result in more showery rain. Also,
cooler air aloft will also result in elevated instability. The
main chances (15-30%) for thunderstorms remains along the coast
on Tuesday, before spreading inland with around a 15-20% chance
of thunderstorms Wednesday afternoon. Any passing thunderstorms
can bring gusty, erratic winds and heavy rain.

Expect southerly wind gusts along the coast, especially beaches
and headlands, approaching 40-50 mph, with just a 10-20% chance
of high wind gusts exceeding 60 mph as an occluding cold front
approaches the coast. Inland areas will mainly see wind gusts of
30 mph or less. While guidance suggests there is only a 5-25%
chance of wind gusts up to 40 mph, with leaves still on the
trees, there is a small chance for a few broken tree limbs or
garbage cans falling over through Tuesday night. Southerly
winds remain slightly elevated through Wednesday with gusts
generally up to 35 mph along the coast and 25 mph inland.

Total rainfall for the Tuesday through Thursday system look to
be around 0.30"-0.50" inland locations, 0.60"-1.60" along the
coast and coast range with 0.30"-1.50" for the Cascades. Higher
total precipitation totals are seen at higher elevations and
areas with more northerly latitudes.

By Friday, most ensemble members are showing drier weather returning
through the weekend. WPC 500 mb cluster analysis shows relatively
good agreement of the upper low dropping into the Great Basin
from Canada by Friday/Saturday. /42-Hartsock

&&

.AVIATION...Expect mostly dry conditions with generally VFR
conditions across the airspace through the first part of the TAF
period. However, a series of frontal systems moving across the
region will bring widespread rain and showers. The warm front
arrives Tuesday morning, with rain beginning along the coast by
15Z-18Z Tue and across the Willamette Valley by 18Z-21Z Tue. The
trailing cold front arrives Tuesday afternoon, with moderate to
high confidence (60-80% chance) in a return of MVFR conditions
along the coast after 18Z Tue. For inland locations, there is
lower confidence (20-30% chance) for MVFR conditions after 21Z
Tuesday. There is also a 20-30% probability for thunderstorms
for locations north of KTMK from 21Z Tue-06Z Wed. Southerly winds
increase across the area beginning 15Z-18Z Tue, with gusts
peaking in the afternoon around 35-40 kt along the coast and 25-30
kt inland. Any passing thunderstorms can bring gusty, erratic
winds and heavy rain which could briefly reduce visibility to
IFR/MVFR thresholds.

KPDX AND APPROACHES...Predominately VFR with a 15-30% chance for
MVFR conditions through 18Z Tue. Rain returns around 18Z-21Z Tue
with the next front, with winds turning southerly and increasing
to 10-15 kt with gusts up to 25 kt. /42

&&

.MARINE...As a surface low deepens west of Vancouver Island
over through Tuesday another, more potent frontal boundary
approaches the coast. This will result in southerly winds
increase through Tuesday. Current guidance is showing peak winds
up to 45 kt across all waters starting early Tuesday morning
through Tuesday night. Isolated storm-force gusts of 48 kt or
more cannot be ruled out. Seas will also build quickly towards
15-19 ft by Tuesday afternoon, although chances for 20 ft or
greater seas have fallen to less than 5%. While winds are
expected to fall below gale-force by Tuesday night, seas will
remain elevated through Wednesday around 14-18 ft and will
continue to slowly subside towards 10-12 ft by Thursday
afternoon. As a result a Gale Warning will come online for the
outer waters by 5am Tuesday and 11am for the inner waters and
the Columbia River Bar, which will continue through late Tuesday
night. Have also upgraded the Hazardous Seas Watches to
Warnings as elevated seas will persist through at least early
Thursday morning.

Behind the Tuesday/Wednesday front, winds are expected to
steadily weaken below 20 kt by Wednesday night and 15 kt by
Thursday evening. Seas expected to subside towards 6-8 ft by early
Friday morning. As the deep low fills and moves inland by this
weekend, it will likely be replaced by building surface high
pressure over the northeastern Pacific which will see winds return
to seasonable northerly flow. /42-Picard

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 11 AM PDT this morning for PZZ210-
     251>253.

     Gale Warning from 11 AM this morning to 2 AM PDT Wednesday for
     PZZ210-251>253.

     Hazardous Seas Warning from 2 AM Wednesday to 8 AM PDT Thursday
     for PZZ210-251>253.

     Gale Warning until 11 PM PDT this evening for PZZ271>273.

     Hazardous Seas Warning from 11 PM this evening to 8 AM PDT
     Thursday for PZZ271>273.
&&

$$

www.weather.gov/portland

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