Raymond, Washington Weather Forecast Discussion

994
FXUS66 KPQR 010650
AFDPQR
Area Forecast Discussion
National Weather Service Portland OR
1150 PM PDT Tue Sep 30 2025
Updated aviation and marine sections.
.SYNOPSIS...A fall-like weather pattern is expected to continue
through much of the week as we transition into October. Expect
periods of rain through at least Thursday as a low pressure system
brings cooler and unsettled weather across the region. Breezy
southerly winds are expected today, followed by rain showers and
chances for thunderstorms as a low pressure system remains offshore.
Any thunderstorm that does develop will bring potential for small
hail, gusty winds, and funnel clouds. Dry weather is expected to
return for the weekend while temperatures remain seasonably cool,
before warming back into the 70s by early next week.
&&
.DISCUSSION...Tonight through Monday...Sunny skies will give way to
increasing clouds and steady rain later this afternoon as a potent
frontal system moves onshore and lifts across the Pacific Northwest.
Satellite imagery shows the associated 972 mb low spinning offshore,
west of Vancouver Island this afternoon. This low pressure system
will then gradually weaken as it meanders toward the WA/OR coast
through Friday.
The initial frontal band will bring a period of steady rainfall,
potentially moderate to heavy at times, as it lifts across NW Oregon
into SW Washington this afternoon. Breezy southerly winds are also
likely with this frontal passage, strongest along the coast,
especially beaches and headlands where wind gusts up to 40-50 mph
will be likely through this evening. Inland areas will mainly see
wind gusts up to 35 mph or less. There remains a very low 5-10%
chance of wind gusts exceeding 45 mph within the Willamette Valley.
With leaves still on the trees, there is a small chance for a few
broken tree limbs.
Behind the front, expect precipitation to become more showery,
continuing through at least Thursday. The cooler air aloft will also
result in elevated instability, with chances for thunderstorms (15-
25%) along the coast today, spreading inland on Wednesday. Any
passing thunderstorm can bring gusty winds, heavy rain, and small
hail. Based on local guidance, this weather pattern also sets up the
potential for funnel clouds as well as water spouts near the coast.
Total rainfall amounts through Thursday are expected to vary
significantly across the area as the rain transitions from
stratiform to showers. This makes it difficult to pinpoint
precipitation amounts at a specific location, but the probabilistic
guidance does provide reasonable low-end to high-end amounts that
will be possible through Thursday. Coastal locations could see
anywhere from 0.50 inch (10th percentile) to 2.50-3.50 inches (90th
percentile); while the inland lowlands are more likely to see a
range between 0.20 to 1.80 in, with highest amounts more likely to
the north. That said in a different way: total rainfall for today
through Thursday is likely (65-85% chance) to exceed 0.5" for valley
locales, with higher chances to the north. Chances to exceed 1" of
rain are the highest along the coast (80-95% chance), in the OR
Coast Range & Willapa Hills (75-90% chance), and in the Cascade
foothills (55-75% chance), and much lower (20-40% chance) within the
Willamette Valley.
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 northern California to
the Great Basin Friday to Saturday. Northwest flow likely to persist
into early weekend with temperatures seasonably cool. There is also
fairly good agreement of an upper level trough dropping out of
Canada on Sunday, bringing more north to northeast flow later Sunday
into Monday with dry conditions and temperatures likely warming back
into the 70s.  /Hartsock
&&
.AVIATION...A weather system continues impacting NW Oregon and SW
Washington through the TAF period, bringing scattered showers and
southerly increased winds to the region. Along the coast, expect
wind gusts up to 25-30 kts through around 09z Wed before decreasing
slightly to 20-25 kts. Gusts expected to increase again after 18z
Wed up to 30-35 kts through 03z Thu. Gusts have decreased across
inland areas with only isolated gusts up to 20-25 kts expected until
after 17-18z Wed when these gusts become more widespread through 00-
03z Thu.
As showery conditions continue, ceilings along the coast are
expected to remain mainly MVFR, though ceilings could occasionally
rise to VFR. Inland areas are expected to remain mainly VFR, though
there`s a 25% chance of MVFR ceilings at terminals such as KHIO,
KSLE, and KEUG through 12-15z Wed. Conditions could lower at any
terminal in any heavier shower. Additionally, thunderstorm chances
increase across the entire region after 18z Wed with a 15-30% chance
of isolated thunderstorms through 06z Thu. Main impacts with any
thunderstorms are brief heavy rain that could lower ceilings or
visibility, gusty winds, and frequent lightning.
KPDX AND APPROACHES...Mainly VFR conditions expected through the TAF
period, though a 15-20% chance of brief MVFR ceilings in showers
continues. South winds around 10 kts with an occasional gust to 20
kts, then after 17-19z Wed, gusts to 20-25 kts possible until 00z
Thu. 20-30% chance of isolated thunderstorms 18z Wed through 03z
Thu. -HEC
&&
.MARINE...Buoy observations indicate gale-force winds have
subsided across the waters, so the Gale Warning has been ended and
replaced with the Hazardous Seas Warning. Latest guidance continues
to indicate a second period of elevated winds from late Wednesday
morning through late Wednesday evening, mainly for zone PZZ251 and
the Columbia River Bar, though guidance has decreased the strength
of these gusts compared to previous forecasts. While winds ease
somewhat overnight, seas will remain elevated through Wednesday
night, with widespread wave heights of 13-17 ft. Hazardous Seas
Warnings remain in effect across all coastal waters and the Columbia
River Bar from tonight through 8 AM Thursday.
Afternoon and evening thunderstorms will pose an additional threat
Wednesday. Storms will be capable of producing severely limited
visibility, gusty and erratic winds, lightning, small hail, and even
an isolated water spout in their local area.
Late in the week, the area of low pressure responsible for this
period of active weather will weaken and move inland while high
pressure builds over the northeastern Pacific. Winds will weaken
below 15 kt while seas subside below 10 ft by Thursday evening,
before the more seasonable patterns turns winds out of the north to
northwest at around 10 kt early Saturday morning. -Picard/HEC
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Hazardous Seas Warning until 8 AM PDT Thursday for PZZ210-
251>253-271>273.
&&
$$
www.weather.gov/portland
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NWS PQR Office Area Forecast Discussion