068
FXUS66 KSEW 101737
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
937 AM PST Wed Dec 10 2025

.UPDATE...Not much change in this morning`s update as an
atmospheric river churns through western Washington. PWAT values
from this morning`s 12z UIL sounding show a new daily record of
1.27" being set, indicative of this moisture-laden airmass
anomalous for this time of the year. Rainfall amounts have
topped out between 4-5" across area mountains since last night.
Rain-shadowing has allowed for lesser totals across the lowlands
with up to 0.50-1.00" so far. Areas immediately downwind of the
Olympics have been spared with even lesser amounts. Widespread
rainfall is expected to persist today, with significant river
flooding on tap. More details are provided below in the hydro
section. The previous discussion remains along with an updated
aviation section:

&&


.SYNOPSIS...
A strong atmospheric system will continue to bring periods of
heavy rain and gusty winds to western Washington through
Wednesday. Widespread significant river flooding is underway
and will continue through the week. 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 /TODAY THROUGH FRIDAY/...
A strong atmospheric river system is well underway across the
Pacific Northwest, with heavy rain pushing into western
Washington this morning. Forecast models have increased
precipitation amounts with this round of incoming moisture,
leading to even higher river forecasts and potential for more
widespread major flooding to occur. Widespread precipitation is
slated to continue region-wide through Thursday morning, with
lingering showers through Friday. This long duration of
precipitation will cause significant rises to area rivers, which
are already running very high. Significant river flooding is
expected to continue through the week, with potential for
flooding impacts to continue into the weekend.

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

* HEAVY RAIN: Widespread heavy rain will continue throughout the
  day today as an atmospheric river remains focused over western
  Washington. This will continue to cause flooding concerns to
  area rivers, urban areas, and areas with poor drainage.
  Forecast models have increased rainfall totals, with an
  additional 1 to 3 inches of rain across the lowlands and
  another 4 to 8 inches over the Olympics and Cascades through
  Thursday morning. Locally higher amounts are possible over
  higher terrain of the western Washington Cascades. A majority
  of area rivers have reached Moderate to Major flood stage,
  with some rivers forecast to break flow records. Rises to area
  rivers will continue with this incoming rainfall, and more
  details can be found in the HYDROLOGY section below.

* WINDS: Breezy winds will continue across western Washington
  tonight into Wednesday, with widespread gusts reaching 40 to
  45 mph. Winds will remain elevated through Wednesday evening
  before gradually weakening into Thursday. The breezy winds,
  combined with deeply saturated soils, raises the risk of
  downed trees and localized power outages Wednesday.

* COASTAL FLOODING: Minor coastal flooding remains possible
  along the northern Salish Sea coastlines during Wednesdays
  high astronomical tide. 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.

While temperatures through the period will be mild with highs in
the low to mid 50s, snow levels will briefly lower in the North
and Central Cascades to 3500-4500 feet Thursday afternoon. This
will result in brief snow accumulations through the higher
passes from Stevens Pass northward.

High pressure will build over the western US on Friday,
amplifying northward into the Pacific Northwest. While
additional systems will continue to bring precipitation into the
region, it will shift northward on Friday. This will allow
shower activity to weaken, with light rainfall amounts lingering
mainly over higher terrain and generally north of the Puget
Sound. While some areas will see drier conditions, area rivers
may remain elevated with flooding concerns continuing.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
Ensembles have keyed in on high pressure continuing to build
northward on 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, with another potentially very wet
system on its heels. It is likely that flooding impacts will
linger into the weekend, and conditions will continue to be
closely monitored.

15

&&

.AVIATION...
Deteriorating conditions are underway as the next wave of moisture
continues to push into the region. Majority of terminals are
IFR/LIFR this morning with visibilities down to 1-3 SM with
mist/moderate to heavy rain. This will continue through Thursday
with marginal improvements. Expect winds to pick up out of the
southwest throughout the day today, with sustained winds at 15-20 kt
gusting to 30-35 kt (possibly up to 40 kt along the coast), then
weakening late this evening. The strongest winds will be in the
southern/central terminals. Some low-speed wind shear can`t be ruled
out with the initial onset of winds, but is primarily expected to be
more of a low-level turbulence issue (with winds aloft staying out
of the southwest below 2,000 ft).

KSEA...IFR ceilings with periods of reduced visibilities during
periods of heavy precipitation. IFR conditions are favored to
persist through much of the day as periods of heavy precipitation
continue. Winds remain out of the southwest at around 15-20 kt with
gusts to 25 to 30 kt this morning, with gusts increasing further to
30 to 40 kt through the afternoon, before decreasing again into
Thursday morning.

MNF/HPR

&&

.MARINE...
An atmospheric river system will continue to bring active
conditions to the Pacific Northwest through Thursday morning.
Moderate to heavy rain over the waters, along with lower
ceilings and areas of fog, may reduce visibilities at times.
Elevated southerly winds will persist into much of Wednesday
across all area waters. West winds will follow in the Strait of
Juan de Fuca late Wednesday evening. Most waters are under
small craft advisories for the breezy winds, with gales through
the Strait of Juan de Fuca and along the inner coastal waters.
Puget Sound waters is the next area being monitored for a
possible upgrade to a gale warning. Winds will decrease below
thresholds Thursday through early next week, before another
system may produce gusty small craft winds for the coastal
waters and interior waters on Sunday.

Seas of 10 to 15 ft will continue through Thursday, subsiding
to 6 to 8 ft by Friday and remaining through the weekend. Seas
will increase once again to 10 to 13 ft early next week.

&&

.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.

     Coastal Flood Advisory until 1 PM PST this afternoon for
     Lowlands of Western Skagit and Northwestern Snohomish
     Counties-Lowlands of Western Whatcom County-San Juan
     County.

     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 10 PM PST this evening for
     Admiralty Inlet-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.

     Gale Warning until 10 PM PST this evening for Central U.S.
     Waters Strait Of Juan De Fuca-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-West
     Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 10 PM this evening to 4 AM PST
     Thursday for Central U.S. Waters Strait Of Juan De Fuca-
     West Entrance U.S. Waters Strait Of Juan De Fuca.

     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.

&&

$$