808
FXUS66 KSEW 042157
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
157 PM PST Thu Dec 4 2025

.SYNOPSIS...
A very active pattern is underway through the next week with a
series of systems bringing rounds of rain, higher elevation
snow, and windy conditions through the end of the week and this
weekend. A more significant atmospheric river event is on track
to reach the area Monday and into early next week for
widespread significant rainfall and hydrologic impacts. Coastal
flooding due to higher astronomical tides will remain minor
into early next week.

&&

.SHORT TERM /TODAY THROUGH SATURDAY NIGHT/...
Rain continues to fall across the area this afternoon. This will
taper off a bit into tonight until another wave moves across the
area Friday bringing a reinforcing round of rainfall. Amounts
will be fairly light across the interior with the heaviest
rainfall focused along the coast, the western Olympics, and
most notably, the Cascades, where 2-3" will be possible through
Saturday afternoon. More details on the hydrologic implications
below. Lowering snow levels Friday night into Saturday morning
will allow a transition to snow at locations down to 4000 ft.
This will allow for a round of significant accumulating
snowfall at Stevens Pass, for which a Winter Weather Advisory
has been issued. Amounts of around 5 to 10" are currently
forecast. Heavy snowfall rates under a convergence zone or in
periods of heavy precipitation may create hazardous conditions.
Windy conditions may limit visibility at time. On that note,
winds will increase Friday into Friday night, with gusts up to
around 20 to 30 mph. Precipitation and winds will taper off
area- wide Saturday night.

Highs Friday and Saturday in the low to mid 50s with lows in the
mid to upper 40s.

Tides will peak Friday along the Pacific coast and Saturday
through the interior waters. Minor coastal flooding will be
possible along the coast, Strait, and north interior waters in
this time frame. Coastal Flood Advisories have been issued as
appropriate.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
The overall long-term forecast remains on track with another
wave of relatively lighter precipitation on Sunday before an
atmospheric river pattern begins to set up Monday and persist
through the rest of the period. During that time, significant
rainfall is expected, with 2-4 inches possible in the lowlands
and 5-10 inches possible in the mountains. Hydrologic impacts
will be significant, but details are listed below.
Additionally, periods of increased wind will accompany the
system, in particular on Monday. Higher snow levels above
5000-6000 ft will allow for rain through the passes and some
snowmelt.

&&

.AVIATION...
Northwesterly flow aloft as a warm front keeps rain and drizzle
across western WA. Murky conditions out there as terminals are
seeing a mix between MVFR/IFR/LIFR conditions. Substantial low
level moisture will likely keep these lowered conditions
throughout the rest of the evening, along with limited vsbys
3-6SM in rain and drizzle. MVFR/IFR will persist into Friday
morning, with lower prone locations (KPWT, KOLM, and even KCLM)
will likely see LIFR conditions. S/SW generally 6 to 8 knots
throughout the evening will increase by Friday morning to 10 to
13 knots.

KSEA...IFR ceilings this afternoon. Ceilings will fluctuate
between IFR and low- end MVFR throughout this evening, although
probabilities have been trending more towards IFR remaining.
Will continue to see vsbys around 4 to 6 statute miles from
light rain and drizzle. Conditions will stay lowered, IFR to
MVFR at times overnight as rain continues. S/SW winds 5 to 10
knots this afternoon will decrease overnight, before increasing
once again by 17z Friday, upwards to 10 to 13 knots. Gusts up to
20 knots can be possible throughout Friday afternoon.

Mazurkiewicz

&&

.MARINE...
A warm front has moved through the waters today for
southerly winds, although they have remained under any criteria.
A stronger front will move over the waters into Friday, which
will result in increasingly strong westerly winds. Latest
guidance has increased since the previous runs, with almost
80-90% of gale gusts over the coastal waters. Therefore, have
upgraded the Gale Watch to a Gale Warning over all of the
coastal waters. Guidance still suggests a 40 to 50% chance of
gale gusts in the inner coastal waters, so have included them as
well. A strong westerly push is also expected in the Strait,
have also upgraded to a Gale Warning for all entrances of the
Strait for Friday evening. Additionally, other interior waters
such as the Puget Sound and Hood Canal zones, and the Northern
Interior waters will see small craft winds during this time.

Additional systems look to move in over the weekend for some
elevated and winds and seas, but look to remain generally on the
mild side. A stronger system on Monday into Tuesday look to
bring winds back up to possibly gale strength, along with
elevated seas.

Combined seas 5 to 7 feet will remain through tonight. Seas
will start to build upwards to 10 feet by Friday afternoon,
building again to 15 to 17 feet by late Friday evening into
Saturday morning.

Mazurkiewicz

&&

.HYDROLOGY...
A series of wet weather systems will increase the threat of
river flooding this weekend, especially into the first half of
next week. West to northwesterly flow aloft with the first
system on Friday will put the area of greatest precipitation in
the North Central Washington Cascades. Snow levels, at this
time, will be rising over 5500 to 6000 feet.

As the flow aloft becomes more westerly to southwesterly the
flood threat will shift to the flood prone Skokomish River late
in the weekend.

There`s still a wide variance in the possible precipitation
amounts with an atmospheric river setting up through the first
part of next week, but confidence is increasing in moderate to
heavy rainfall across western WA, especially over the Olympics
and Cascades.

Confidence is increasing that we will see a widespread river
flooding event on our hands beginning late Monday, throughout
Tuesday and into Wednesday, with multiple rivers flowing off the
Cascades and the Olympics reaching minor and moderate flood
stages (potentially nearing even Major flood stage).

Uncertainty still continues to remain in regards to the exact
flood levels and stages through next week, and as such it will
be critical to monitor the forecasts through the next seven
days.

The series of wet systems will start to elevate the landslide
risk throughout the weekend, increasing rapidly early next week
with the arrival of an atmospheric river.

Mazurkiewicz

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Coastal Flood Advisory from 4 AM to 10 AM PST Saturday for
     Lowlands of Western Skagit and Northwestern Snohomish
     Counties-Lowlands of Western Whatcom County-San Juan
     County.

     Winter Weather Advisory from 7 PM Friday to 10 PM PST Saturday
     for Cascades of Snohomish and Northern King Counties.

     Coastal Flood Advisory from 9 AM to 3 PM PST Friday for
     Eastern Strait of Juan de Fuca-Grays Harbor County Coast-
     Northern Washington Coast-Western Strait of Juan de Fuca.

     Coastal Flood Advisory from 9 AM to 3 PM PST Saturday for
     Grays Harbor County Coast.

PZ...Gale Warning from 1 PM Friday to 4 AM PST Saturday for West
     Entrance U.S. Waters Strait Of Juan De Fuca.

     Gale Warning from 1 PM Friday to 7 AM PST Saturday for Central
     U.S. Waters Strait Of Juan De Fuca-East Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 1 PM Friday to 10 AM PST Saturday
     for Northern Inland Waters Including The San Juan Islands.

     Small Craft Advisory from 1 PM Friday to 4 AM PST Saturday for
     Puget Sound and Hood Canal.

     Gale Warning from 10 AM Friday to 4 AM PST Saturday for
     Coastal Waters From Cape Flattery To James Island 10 To
     60 Nm-Coastal Waters From Cape Flattery To James Island
     Out 10 Nm-Coastal Waters From James Island To Point
     Grenville 10 To 60 Nm-Coastal Waters From James Island To
     Point Grenville Out 10 Nm-Coastal Waters From Point
     Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters
     From Point Grenville To Cape Shoalwater Out 10 Nm.

&&

$$