726
FXUS66 KSEW 110007
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
407 PM PST Wed Dec 10 2025

.SYNOPSIS...
A persistent atmospheric river will continue to bring periods
of moderate to heavy rain and gusty winds to western Washington
through tonight. Widespread significant river flooding is
underway and will continue through the next couple of days.
Minor coastal flooding due to astronomical high tides will also
pose concerns for the northern Salish Sea coastlines through
much of the week. Wet and unsettled conditions will continue
into early next week.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...
A strong atmospheric river is currently ongoing across western
Washington bringing a flurry of impacts including widespread
moderate to heavy rainfall. Cascade foothills have been hit
exceptionally hard with over 4.00" of rainfall observed for
locations such as Skykomish and Grotto so far today. Moisture-
laden soils have been become unstable, leading to reports of
landslides. This amount of rainfall has also lead to a plethora
of swollen rivers in flood stage. More hydrological detail is
provided in the hydro section below.

The following key messages with this atmospheric river are
outlined below:

* HEAVY RAIN: Current satellite imagery shows a long fetch of
  cloud coverage spanning near the vicinity of the Hawaiian
  islands to the PNW. This airmass of tropical origin is the
  atmospheric river that will continue to bring widespread
  moderate to heavy rainfall into early Thursday. A nose of
  forecast IVT values are exceeding 700 kg/ms, entering WA this
  evening but should subside overnight into Thursday morning.
  This coincides well with stout 850 mb winds upwards of 50-55
  kt, serving as a conduit of precipitation generation along the
  Olympics and Cascades. An additional 4-8" of rainfall is in
  the forecast for the mountains through Thursday morning. Can`t
  rule out localized higher amounts. 3-6" is favored for the
  foothills and rain shadowing will keep the lowlands with lower
  totals, with 1-3" expected. Rain shadowed areas of Kitsap
  Peninsula and Admiralty Inlet won`t exceed an inch. The
  atmospheric river will gradually taper off into Thursday
  afternoon but can`t rule out lingering showers and residual
  river flooding.

* WINDS: Breezy winds will continue across western Washington
  this evening, with gusts reaching 40 mph. Winds will gradually
  lessen overnight into Thursday morning but with water-logged
  soils, downed trees and localized power outage can`t be rule
  out during this time.

As mentioned, the atmospheric river will taper off by Thursday
afternoon. However, lingering showers will remain in the
forecast through Saturday before upper-level ridging builds and
displace disturbances well off to our north. Temperatures in the
short-term forecast will remain well-above average with highs in
the lower to mid 50s, between 5-10 degrees above average this
time of the year.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As mentioned, ensembles have signaled high pressure amplifying
over the region into Saturday, potentially bringing some relief
to continued wet conditions across western Washington. This
will be short lived, with the next weather system on track to
cross the Pacific Northwest on Sunday as a weak cold front
enters. Additionally, a potentially very wet system on its
heels into Monday. It is likely that flooding impacts will
linger into the weekend, and conditions will continue to be
closely monitored, even with precipitation dwindling in
intensity.


&&

.AVIATION...
An atmospheric river system will continue to produce
widespread visibility and ceiling impacts due to heavy rain this
afternoon and evening, as well as gusty winds. Terminals are
primarily reporting IFR this afternoon (with pockets of MVFR and
LIFR). Low level moisture and additional rain (some of which may be
heavy at times) will likely keep visibilities down in most terminals
through tonight/Thursday, with rain diminishing during the day
Thursday. Ceilings are expected to be slow to improve to MVFR
through the afternoon, with a low probability of improvement out of
IFR in the south terminals through the day Thursday. Winds this
afternoon remain breezy out of the southwest at 15-25 kt gusting to
35 kt. Speed shear remains more of a concern (compared to direction
shear) with southwest winds expected at higher speeds aloft. Winds
will decrease early Thursday morning down to 5-10 kt. A push of
northwesterlies through the Strait of Juan de Fuca will turn winds
briefly north/northeast in the Puget Sound terminals between 06Z-
12Z, before returning to the south. Winds will become calm to light
and variable by Thursday afternoon.

KSEA...IFR conditions likely to continue through the TAF period with
rain (some of which may be moderate to heavy at times), low ceilings
and mist. Small chance for improvement to MVFR late Thursday
afternoon before returning to IFR in the evening. Winds SW 10-15 kt
gusting to 30 kt through roughly 12Z, then a brief window of NE
winds 5-10 kt between 12-16Z before returning to the ESE. Winds drop
to under 5 kt late Thursday afternoon, become light and variable.

HPR


&&

.MARINE...
A frontal system associated with an atmospheric river will
continue to push across the region through Thursday. Moderate to
heavy rain and areas of mist will reduce visibilities at times.
Winds remain breezy out of the southwest this afternoon, with a few
gale force gusts still possible in the inner coastal waters through
the evening. Headlines remain in place for small craft elsewhere.
Post-front, the winds will turn west through the Strait of Juan de
Fuca tonight into the Admiralty Inlet. Winds will decrease
substantially going into late Thursday, with rain showers tapering
back as high pressure moves in. Another system next weekend will
likely produce another round of strong southwest winds. At this
time, there is a medium chance for gale gusts in the coastal waters
Sunday and Monday, and in the Strait of Juan de Fuca Monday and
Tuesday.

Seas Wednesday at 8 to 12 ft will decrease to 6 to 8 ft Friday
through Sunday, increasing to 12 to 16 ft early next week with the
next system.

HPR

&&

.HYDROLOGY...
Most rivers across western Washington will be
affected by this second wave of AR moisture and many flood
warnings remain in effect. Consult weather.gov/seattle for the
latest. While some uncertainty does still remain in regards to
the exact flood levels and stages, many river forecast points
are projected to reach major flood stage and may even approach
or exceed the previous floods of record. It will be critical to
monitor the forecasts now and through the next seven days.

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.


&&

.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.

     Wind Advisory until 10 PM PST this evening for City of Seattle-
     Downtown Everett / Marysville Area-Eastern Kitsap County-
     Eastside-Foothills of the Western and Southern Olympic
     Peninsula-Grays Harbor County Coast-Lower Chehalis River
     Valley-Lowlands of Lewis and Southern Thurston Counties-
     Lowlands of Pierce and Southern King Counties-Middle
     Chehalis River Valley-Northern Washington Coast-Olympia
     and Southern Puget Sound-Shoreline / Lynnwood / South
     Everett Area-Southern Hood Canal-Willapa and Black Hills.

PZ...Small Craft Advisory until 4 AM PST Thursday for Admiralty
     Inlet-Central U.S. Waters Strait Of Juan De Fuca-East
     Entrance U.S. Waters Strait Of Juan De Fuca-Grays Harbor
     Bar-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 until 10 PM PST this evening for Coastal Waters
     From Cape Flattery To James Island Out 10 Nm-Coastal
     Waters From James Island To Point Grenville Out 10 Nm-
     Coastal Waters From Point Grenville To Cape Shoalwater
     Out 10 Nm.

     Small Craft Advisory from 10 PM this evening to 4 AM PST
     Friday for Coastal Waters From Cape Flattery To James
     Island Out 10 Nm-Coastal Waters From James Island To
     Point Grenville Out 10 Nm-Coastal Waters From Point
     Grenville To Cape Shoalwater Out 10 Nm.

     Small Craft Advisory until 4 AM PST Friday for Coastal Waters
     From Cape Flattery To James Island 10 To 60 Nm-Coastal
     Waters From James Island To Point Grenville 10 To 60 Nm-
     Coastal Waters From Point Grenville To Cape Shoalwater 10
     To 60 Nm.

&&

$$