926
FXUS66 KSEW 060937
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
137 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/...
Western Washington will see heightened winds continue this
morning, lightening up just before daybreak. Westerly wind gusts
are still pushing 45 to 50 mph at the time of this writing,
primarily along the coast and portions of the Cascades.
Convergence zone activity is ongoing in Snohomish and Skagit
Counties, where a winter storm warning remains in effect.
Precipitation is also continuing in the southern Cascades and
through White Pass, with more expected for both locations later
on today. Precipitation is expected throughout the day, tapering
slightly by this afternoon. The break is going to be short lived
as another system pushes in on Sunday. Rainfall over the weekend
will be focused more so in the Cascades, where 2 to 5 inches
are forecast. At the higher elevations, particularly today as
snow levels are lower at around 4000 ft, upward of 12 to 18
inches of new snow is expected at Stevens Pass and 10 to 15
inches at White Pass. A wintry mix is possible at Snoqualmie
Pass today.
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
11-15 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 continues through today in a post-
frontal airmass. VFR/MVFR cigs early this morning with strong
onshore flow at the surface. VFR/MVFR cigs will continue through
this evening. Cigs will then lower late tonight into Sunday
morning as another frontal system moves into Western Washington.
Shower activity 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
will peak through this morning, mainly ranging 20 to 30 kts,
with stronger gusts at times through 15-18z around SEA/BFI with
continued onshore flow.
KSEA...MVFR cigs early this morning in a post-frontal airmass.
Predominantly MVFR cigs expected through 21z, although some
improvements to VFR may occur at times. Some further improvements
expected this afternoon into this evening towards VFR. Cigs will
then lower again later tonight into Sunday morning ahead of the next
frontal system. Gusty SW surface winds through 15-17z, with gusts
ranging 25 to 35 kts. Winds will slowly subside this afternoon, but
remain elevated before winds further taper off this evening. JD
&&
.MARINE...
Strong onshore flow continues early this morning across the
waters in a post-frontal airmass. Gales will continue through
the Strait of Juan de Fuca this morning, with localized gusts of
45 kts at times. Gales also continue for Puget Sound and
northern inland waters through mid-morning. Small Craft Advisory
winds follow the gales this afternoon as winds subside, but
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 of 14 to 19 feet this morning will slowly subside to 8 to 9
feet late tonight into Sunday. Seas will then build above 10 feet on
Monday and remain above 10 feet through midweek. JD
&&
.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 possible 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, throughout Tuesday and
into Wednesday, with multiple rivers flowing off the Cascades and
the Olympics reaching 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 throughout the weekend, with conditions
expected increase rapidly early next week with the arrival of an
atmospheric river.
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 from 4 AM to 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.
Wind Advisory until 3 AM PST early this morning for City of
Seattle-Lowlands of Pierce and Southern King Counties-
Olympia and Southern Puget Sound.
Coastal Flood Advisory from 9 AM this morning to 3 PM PST this
afternoon for Grays Harbor County Coast.
Wind Advisory until 7 AM PST this morning for Island County.
PZ...Small Craft Advisory until 10 PM PST this evening for Grays
Harbor Bar.
Gale Warning until 4 AM PST early this morning 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-Puget Sound and
Hood Canal-West Entrance U.S. Waters Strait Of Juan De
Fuca.
Small Craft Advisory from 4 AM early this morning to 10 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-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 4 AM PST early this morning for
Admiralty Inlet.
Gale Warning until 7 AM PST this morning for Puget Sound and
Hood Canal.
Small Craft Advisory from 7 AM this morning to 4 PM PST this
afternoon for Puget Sound and Hood Canal.
&&
$$
NWS SEW Office Area Forecast Discussion