907
FXUS66 KSEW 080933
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
133 AM PST Mon Dec 8 2025

.SYNOPSIS...
A strong atmospheric river will bring periods of moderate to
heavy rainfall and gusty winds to western Washington through
Wednesday, with high risk of significant river flooding across
the region through much of the week. Minor coastal flooding due
to high astronomical high tides will also remain possible for
the Salish Sea coastlines through the first part of the week.
Wet and unsettled conditions will continue through the end of
the week.

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY/...
Light post-frontal shower activity continues this morning across
much of western Washington in the wake of an approaching
atmospheric river storm system. South to southwesterly winds
will continue to pick up this morning, with widespread moderate
to heavy rain filling in along the coast by mid morning, and
across most of western Washington by the afternoon.

Conditions will become wetter throughout the day today as a
strong atmospheric river moves into the Pacific Northwest. This
system will impact the region through Wednesday, with a series
of impacts through the week. The key messages regarding this
system are highlighted below:

* HEAVY RAIN: A strong atmospheric river will move into the
  Pacific Northwest today, bringing extended periods of moderate
  to heavy rain to western Washington through Wednesday. Latest
  forecast models have remained fairly consistent, with the
  heaviest rainfall arriving today. The moisture plume still
  looks to briefly shift southward on Tuesday for a lull in
  activity for some areas before lifting back northward late
  Tuesday through Wednesday. While areas east of the Olympics
  will likely see some shadowing at the onset of precipitation,
  conditions across all of western Washington will be very wet
  through Wednesday. Areas generally south of Seattle will see
  3 to 6 inches of rainfall through Thursday morning in a 72
  hour period, with the Olympics and Cascades on track to see 6
  to 10 inches of rain in this timeframe. Locally higher amounts
  are possible over the southern and central Cascades, where
  amounts could reach 12 inches or more in 72 hours. This is
  expected to bring significant river flooding to western
  Washington, with many area rivers forecast to reach moderate
  or major flood stage by mid-week. A Flood Watch remains in
  effect for all of western Washington through Friday morning.
  For more details, see the HYDROLOGY section below.

* WIND: Conditions will be windy area-wide today, with
  southwesterly winds picking up throughout the day. Winds will
  peak this evening, with the strongest gusts along the Pacific
  Coast reaching 50-55 mph. Gusts elsewhere across the interior
  will reach 40-45 mph at times. Winds will gradually ease into
  Tuesday, but conditions will remain breezy at times.

* COASTAL FLOODING: Minor coastal flooding remains possible
  along the Salish Sea coastlines through the first half of the
  week with high astronomical tides. While the tides will
  generally remain below or nearing thresholds, heightened river
  flows or wind effects could exacerbate inundation in some
  areas around high tide.

In addition, snow levels will briefly lower to near 3500-4000
feet over the mountains Tuesday as the track of the atmospheric
river shifts southward, resulting in accumulating snow
generally above 4500 feet. The higher mountain passes, including
Stevens Pass and White Pass, will likely see a few inches of
snow accumulation throughout the day Tuesday which could cause
brief slippery travel conditions.

Incoming moist air from the central Pacific will also maintain
warmer temperatures across the region through the week.
Temperatures will peak well above normal most days this week,
with temperatures in the low to upper 50s across the lowlands.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
Unsettled conditions are favored to continue into the weekend,
though precipitation amounts will start to taper across western
Washington by Thursday. Ensemble guidance continues to show
potential for a brief break in precipitation for some areas
towards the weekend, showing ridging along the western US coast
nudging the atmospheric river northward. However, the track of
this system remains somewhat uncertain this far out. Forecast
models continue to indicate a series of additional systems over
the weekend and beyond bringing in additional precipitation and
breezy winds to the region, though these systems look much
weaker than what we will see early this week.

15

&&

.AVIATION...
Strong westerly aloft is expected over Western Washington as a warm
front lifts northward across the area today with a trailing cold
front crossing the region late tonight. Predominant low MVFR
ceilings in increasing rain are expected into this afternoon.
Further deterioration in ceilings and visibility is expected with
the arrival of the warm front...leading to areas of IFR ceilings and
surface visibility reduced to 3 to 5 statute miles in moderate to
locally heavy rainfall. Surface winds will increase by afternoon
with south to southwest winds of 20 to 30 knots at times with
locally higher gusts. Low level wind shear will also be a
consideration...especially 18Z through around 05Z tonight.

KSEA...Low MVFR in increasing rain expected this morning. Conditions
are expected to deteriorate further by late afternoon with
occasional IFR and surface visibility reduced to 3-5SM in moderate
to locally heavy rain. Surface winds southerly 10 to 15 knots early
becoming S/SW 15 to 25 knots by 18Z with gusts 30 to 40 knots
expected 21Z through 04Z.

27

&&

.MARINE...
A warm front will lift northward across the waters today with a
trailing cold front arriving tonight. This will lead to gales across
much of the waters this afternoon into tonight. High pressure
briefly builds into the coastal waters early Tuesday before a
secondary frontal system arrives late Tuesday into Tuesday night.
The parent low with this system will remain well north of the
region, but it will still generate headlines for all waters. The
pattern will remain rather active into the second half of the week
as a series of fronts move across the area.

Seas will build to 13 to 16 feet today and remain in double digits
through midweek before subsiding below 10 feet late Thursday into
Friday.

27

&&

.HYDROLOGY...
A strong atmospheric atmospheric will move through the Pacific
Northwest Monday through Wednesday, bringing significant heavy
rainfall across the area. 72-hour precipitation amounts between
Monday morning and Thursday morning will likely reach 2 to 6
inches across the lowlands, with 6 to 10 inches over the
Olympics and Cascades with locally higher amounts up to 12
inches over the central and southern Cascades. Rivers will start
to sharply rise on Monday, with many area rivers reaching flood
stage by later this evening. Confidence remains high that a
widespread significant river flooding event will commence late
Monday and continue through much of the week.

Many rivers flowing off the Cascades and the Olympics are
forecast to reach Minor, Moderate, and Major flood stage between
this evening and Tuesday, where many of them are forecast to
remain through Thursday. While some uncertainty does still
remain in regards to the exact flood levels and stages through
the next week, it will be critical to monitor the forecasts now
and through the next seven days. Additional precipitation is
also possible Thursday into Friday, which may keep rivers
elevated heading into the weekend. A Flood Watch remains in
effect across all of western Washington through Friday.

With the wet antecedent soil conditions, the landslide threat
across the region will increase with this system. Potential has
also increased for debris flows over area burn scars, which will
continue to be monitored.

Urban and small stream flooding, as well as areas with poor
drainage, should be alert to the potential for localized nuisance
flooding and ponding on roadways. Low water crossings may become
impacted or impassable.

15

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Flood Watch through Friday afternoon for Cascades of Pierce
     and Lewis Counties-Cascades of Snohomish and Northern
     King Counties-Cascades of Southern King County-Cascades
     of Whatcom and Skagit Counties-City of Seattle-Downtown
     Everett / Marysville Area-Eastern Kitsap County-Eastern
     Strait of Juan de Fuca-Eastside-Foothills and Valleys of
     Central King County-Foothills and Valleys of Pierce and
     Southern King Counties-Foothills and Valleys of Snohomish
     and Northern King Counties-Foothills and Valleys of
     Thurston and Lewis Counties-Foothills and Valleys of the
     North Cascades-Foothills of the Western and Southern
     Olympic Peninsula-Grays Harbor County Coast-Island County-
     Lake Crescent Area Including US 101-Lower Chehalis River
     Valley-Lowlands of Lewis and Southern Thurston Counties-
     Lowlands of Pierce and Southern King Counties-Lowlands of
     Western Skagit and Northwestern Snohomish Counties-
     Lowlands of Western Whatcom County-Middle Chehalis River
     Valley-Northern Hood Canal-Northern Washington Coast-
     Olympia and Southern Puget Sound-Olympics-Port Townsend
     Area-San Juan County-Shoreline / Lynnwood / South Everett
     Area-Southern Hood Canal-Western Strait of Juan de Fuca-
     Willapa and Black Hills.

     Coastal Flood Advisory from 6 AM this morning to noon PST
     today for Lowlands of Western Skagit and Northwestern
     Snohomish Counties-Lowlands of Western Whatcom County-San
     Juan County.

     Wind Advisory from 7 AM this morning to 10 PM PST this evening
     for City of Seattle-Downtown Everett / Marysville Area-
     Eastern Kitsap County-Eastside-Foothills and Valleys of
     Central King County-Foothills and Valleys of Pierce and
     Southern King Counties-Foothills and Valleys of Snohomish
     and Northern King Counties-Foothills and Valleys of
     Thurston and Lewis Counties-Foothills and Valleys of the
     North Cascades-Island County-Lowlands of Lewis and
     Southern Thurston Counties-Lowlands of Pierce and
     Southern King Counties-Lowlands of Western Skagit and
     Northwestern Snohomish Counties-Lowlands of Western
     Whatcom County-Northern Hood Canal-Olympia and Southern
     Puget Sound-Port Townsend Area-San Juan County-Shoreline
     / Lynnwood / South Everett Area-Southern Hood Canal-
     Willapa and Black Hills.

     Wind Advisory until 10 PM PST this evening for Eastern Strait
     of Juan de Fuca-Foothills of the Western and Southern
     Olympic Peninsula-Grays Harbor County Coast-Lake Crescent
     Area Including US 101-Lower Chehalis River Valley-Middle
     Chehalis River Valley-Northern Washington Coast-Western
     Strait of Juan de Fuca.

PZ...Small Craft Advisory from 10 AM this morning to 4 AM PST
     Tuesday for Grays Harbor Bar.

     Gale Warning from 10 AM this morning to 10 PM PST this evening
     for Admiralty Inlet-East Entrance U.S. Waters Strait Of
     Juan De Fuca-Northern Inland Waters Including The San
     Juan Islands-Puget Sound and Hood Canal-West Entrance
     U.S. Waters Strait Of Juan De Fuca.

     Gale Warning from 1 PM this afternoon to 10 PM PST this
     evening for Central U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 10 AM PST this morning for
     Admiralty Inlet-East Entrance U.S. Waters Strait Of Juan
     De Fuca-Northern Inland Waters Including The San Juan
     Islands-Puget Sound and Hood Canal.

     Gale Warning from 7 AM this morning to 7 PM PST this evening
     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.

&&

$$