888
FXUS66 KSEW 061657
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
857 AM PST Sat Dec 6 2025

.SYNOPSIS...
Active weather continues, with a certain increase in activity as
a strong atmospheric river arrives early next week. Heavy rain,
river flooding, wind and high elevation snow are in the forecast
for the foreseeable future. Coastal flooding due to high
astronomical tides will remain minor into the first part of the
week.

&&

.SHORT TERM /TODAY THROUGH MONDAY/...
This morning, winds have begun to ease with gusts now peaking at
around 25-35 mph across the area. Winds will continue to be
breezy through this afternoon but should slowly ease later
today. Additionally, while moderate to heavy
precipitation continues to persist across the mountains and
portions of southwest Washington, temperatures at Stevens and
White Pass sit just above freezing, indicating that snow levels
are hovering just above pass level. Winter headlines currently
remain as is but will likely need to be downgraded/expired this
afternoon as water vapor imagery shows the shortwave trough axis
currently crossing the Cascades as of 9AM this morning.

Coastal flood advisories remain in effect for the Grays Harbor
coast, San Juan Islands, Western Whatcom county and portions of
Snohomish county through the weekend. Only minor coastal
flooding is expected for the high tide cycles through Sunday.
Higher waves along the Grays Harbor county coastline (generally
12-16 ft) will need to be monitored as it could compound
effects from the tides today. More on this can be found in the
marine section.

The strong atmospheric river will arrive beginning on Monday,
bringing with it a very impressive moisture source (750-1000
kg/m/s) for heavy rain over the next several days. In addition
to the attention-grabbing moisture source values, the duration
of the event will compound impacts in the region. Rain will be
continuous on Monday, with a secondary pulse arriving Tuesday
and lasting into early Wednesday. In the long term section, a
Key Points format will be outlined to discuss all hazards for
the week associated with the atmospheric river.

21

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
KEY MESSAGES:

* RAIN: High QPF amounts are forecast to accompany this potent
  atmospheric river Monday through Wednesday. 3 to 6 inches of
  rain are forecast from Seattle south to Olympia and 2 to 4 inches
  from around Everett north. Cascade and adjacent foothill
  locations are still on track to receive around 10 inches of
  rain as snow levels climb again. Forecast indications at this
  point are for additional atmospheric rivers in the wake of the
  strong one to bring even more rain in the second half of the
  week. QPF at this point suggest another 1 to 2 inches in the
  lowlands, and 2 to 5 inches more in the mountains. There will
  be hydrologic implications of this much rain that will be
  detailed in that section of this discussion.

* SNOW: True to an atmospheric river, snow levels will climb to
  6000-7500 ft by Monday afternoon. Snow amounts will be
  confined to peaks and volcanoes above 7500 feet through
  Wednesday but could be longer into the second half of the week.

* WIND: Breezy to windy conditions are expected with the onset
  of the atmospheric river event. The winds will start on the
  coast Monday morning, picking up further inland into the
  afternoon and evening. Gusts of 35 to 40 mph are in the
  forecast. As the event continues into the middle of the week,
  the wind threat diminishes, with only breezy conditions at
  times through Wednesday.

* LANDSLIDES: Continued heavy rain will increase the threat of
  landslides. Area burn scars will be monitored throughout the
  event, but slides are possible elsewhere as well.

21

&&

.AVIATION...
West-northwest flow aloft will continue through today in a
post- frontal airmass. Primarily VFR/MVFR cigs this morning with
breezy onshore flow at the surface. VFR/MVFR cigs will continue
through this evening before lowering late tonight into Sunday
morning as another frontal system moves into Western Washington.
Shower activity will be around through this afternoon as well,
with drier conditions around SEA to PAE due to shadowing from
the Olympics. Breezy SW surface winds through midday before
winds slowly taper later this afternoon, and further taper off
tonight. Gusts between 20 to 30 kts will remain possible through
this morning, with stronger gusts possible at times through 18Z
around SEA/BFI.

KSEA...MVFR cigs continue this morning in a post-frontal
airmass and are expected to continue through 21Z, although some
improvements to VFR may occur at times. Some further improvements
towards VFR expected by this afternoon. Cigs will then lower
again later tonight into Sunday morning ahead of the next
frontal system. Gusty SW surface winds through 18Z, with gusts
ranging 25 to 35 kts. Winds will slowly subside this afternoon,
but remain breezy before winds really ease this evening. JD/14

&&

.MARINE...
Strong onshore flow continues early this morning across the
waters in a post-frontal airmass. Gales will ease over the next
few hours through the Strait of Juan de Fuca. Small Craft
Advisory winds will follow the gales this afternoon as winds
subside, but overall conditions will remain elevated over the
majority of waters. Winds will then briefly subside below SCA
thresholds tonight. South winds will increase Sunday morning
associated with the next weather system that will move across
the waters on Sunday. SCA wind gusts are expected for the Coast
Sunday morning. SCA southerly winds may also occur on Sunday for
the interior waters, and will need to monitor this for further
headlines. A stronger weather system will then move into the
waters Monday into Tuesday for increased winds, and likely
additional gale and SCA headlines. Additional weather systems
expected mid to late next week.

Seas over the coastal waters generally range between 14 to 20
feet this morning will slowly subside to 9 to 11 feet by late
tonight into Sunday. Seas will then build above 10 feet on
Monday and remain above 10 feet through midweek. JD/14

&&

.HYDROLOGY...
A series of wet weather systems moving across the region will
increase the threat of river flooding early next week. While
there`s still some uncertainty in the precipitation amounts
with an atmospheric river moving into the region the first part
of next week, confidence continues to increase in heavy rainfall
occuring across western WA, especially over the Olympics and
Cascades.

Confidence also continues to increase that a widespread river
flooding event will commence late Monday and continue through
much of the week, with multiple rivers flowing off the Cascades
and the Olympics forecast to reach Minor, Moderate, and Major
flood stage. Additional precipitation is also possible Thursday
into Friday, which will keep rivers elevated through the second
half of the week.

Uncertainty does 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 also start to elevate the landslide
risk across the region. As soils become more saturated next week,
there will be an increased potential for landslides and debris
flows on burn scars.

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

14/62

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Coastal Flood Advisory until 10 AM PST this morning for
     Lowlands of Western Skagit and Northwestern Snohomish
     Counties-Lowlands of Western Whatcom County-San Juan
     County.

     Coastal Flood Advisory from 5 AM to 11 AM PST Sunday for
     Lowlands of Western Skagit and Northwestern Snohomish
     Counties-Lowlands of Western Whatcom County-San Juan
     County.

     Flood Watch from late Sunday night 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.

     Winter Storm Warning until 10 PM PST this evening for Cascades
     of Snohomish and Northern King Counties.

     Winter Weather Advisory until 7 PM PST this evening for
     Cascades of Pierce and Lewis Counties.

     Coastal Flood Advisory until 3 PM PST this afternoon for Grays
     Harbor County Coast.

PZ...Small Craft Advisory until 10 PM PST this evening for Grays
     Harbor Bar.

     Small Craft Advisory until 1 PM PST Sunday 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-West Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Gale Warning until 10 AM PST this morning for Central U.S.
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
     Strait Of Juan De Fuca-Northern Inland Waters Including
     The San Juan Islands.

     Small Craft Advisory until 7 PM PST this evening for Central
     U.S. Waters Strait Of Juan De Fuca-East Entrance U.S.
     Waters Strait Of Juan De Fuca-Northern Inland Waters
     Including The San Juan Islands.

     Small Craft Advisory until 4 PM PST this afternoon for Puget
     Sound and Hood Canal.

&&

$$