944
FXUS66 KSEW 160005
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
405 PM PST Mon Dec 15 2025

.SYNOPSIS...
An atmospheric river will continue to produce impacts across
western Washington through the week. The first round of rain
will wrap up tonight, with a second system moving through
Tuesday into Wednesday. This second system will bring in cooler
air, along with mountain snow, and additional rain to the
lowlands and mountain slopes. An additional system will pass
through Thursday into Friday, with lighter precipitation into
the weekend. Winds will continue to diminish tonight, with
another round of gusty winds arriving Tuesday night into
Wednesday.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
This afternoon: the first round from this atmospheric river
continues across western WA this afternoon. The cold front is
progressing through, with the mode shifting more from stratiform
precipitation to convective/showery activity. The atmosphere
remains conditionally unstable going into the afternoon
(especially in the Cascades and the coast). A few showers have
formed in these areas that have elevated quickly. There remains
a 20% chance of thunder going into the evening. The heaviest of
these showers/storms may produce rainfall rates up to 0.25"/hr
(which may be a concern for a few of the newer burn scars in the
Cascades). Aerial and river flooding continue to be an issue
with the heavier precipitation that fell earlier today/yesterday.
Please see the hydrology section below for more details on
flooding potential and current impacts. Lastly, breezy winds
continue with this first system, and a wind advisory remains in
effect until 10 PM as winds decrease later tonight. The saturated
soils will produce more widespread power outage impacts (in
relation to trees and power lines potentially coming down).

Tuesday/Wednesday: A second frontal system will bring another
round of precipitation across the region. The bulk of this
precipitation will arrive late Tuesday morning, and continue
through Wednesday afternoon. The cold front with this system is
expected to bring cooler air down with snow levels dropping from
6,000 ft down to 2,000 ft. There remains a 10-20% chance of
thunder with this system, especially along the coast.

Impacts: Winds will pick up Tuesday into Wednesday, decreasing
Wednesday afternoon. The ensemble guidance between the HREF/REFS
and NBM kept the most likely wind impacts in the advisory range.
The high wind watch was replaced with a wind advisory through
the period. Southwest winds of 15 to 30 mph are expected in the
advisory areas, with gusts up to 45 to 55 mph (highest gusts
along the Pacific Coast).

Rain will transition to snow in the Cascades/Olympics late
Tuesday night/Wednesday morning. Some model discrepancies remain
with how quick the transition will take place, but models
relatively agree on set amounts between the north Cascades, and
the south Cascades/Olympics. The north Cascades will see warning
amounts of snow with 10-16 inches at Stevens Pass, and higher
amounts at some of the mountain peaks. The south Cascades and
Olympics will likely see advisory amounts, with 6-10 inches at
Snoqualmie and White Passes. Breezy winds up to 35 mph in the
passes may reduce visibilities and near-blizzard like conditions
at times (especially with the heavier snow). If traveling over
the passes, check road conditions prior to traveling.

For all remaining lowlands: rain will push through late Tuesday
morning through early Wednesday afternoon. The heaviest of the
precipitation rates remain in the mountains, but the lowlands
may see rates approach 0.10"/hr (lighter than previous systems).
Additional rainfall amounts of 0.75-1.25" are expected in the
interior, with the coast seeing around 1.00-1.25".

In addition to rain and wind, landslide risk will remain high
through the week due to saturated soils from last week (and this
week`s) rainfall across the region. Strong waves along the
Pacific Coast will be possible at times today through Wednesday
as waves of 15 to 19 ft move up to the coast. High surf is not a
concern at this time.

Temperatures will remain above average Tuesday, with highs
remaining in the mid 50s. They will dip into the 40s on
Wednesday. The lows overnight will drop from the mid 40s
tonight, to the low 40s Tuesday and Wednesday night.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
A third system will move across the region Thursday into Friday.
The snow levels will remain around 2,000 ft with this system,
adding additional snow to the passes. QPF will be heavily
concentrated in the Cascades and Olympics, but amounts overall
are on the lighter side compared to the previous two systems
(0.50-1.00" in the lowlands, and 1-3" in the mountains). Light
QPF will continue through the weekend, with no additional
impacts expected. The ensembles favor a cooler pattern going
into the holidays next week, with a slight chance of wetter
conditions.

HPR

&&

.AVIATION...
Strong west to southwest flow aloft continues the
entire TAF period. The cold front that brought light rain and
reduced flight conditions to the area will be exiting the region at
the beginning of this TAF period. Another cold front is on track to
traverse across the area Tuesday afternoon and bring more rain,
gusty winds, and reduced flight conditions.

Gusty 25kt to 35kt winds will begin diminishing around 02/03Z as
mixing largely subsides. Winds largely remain around or less than
10kts overnight before increasing as the next front reaches the
region late in the TAF period. Gusts of 20kts to 30kts return after
20Z Tuesday at most terminals.

Light rain will continue to dissipated through 02Z/03Z across the
area with VFR flight conditions at all terminals. However, isolated
instances of MVFR ceilings / a 3000ft deck cannot be ruled out.
Ahead of the next weather system, IFR to MVFR ceilings begin to roll
into the terminals. The most likely timeframe of reduced flight
conditions beginning will be roughly between 08Z-13Z. These reduced
flight conditions continue through the remainder of the TAF period.
Light rain to rain shower potential increases ahead and with the
front on Tuesday morning.

KSEA... Light rain and gusty 25kt to 35kt winds will come to an end
around 03Z. Through 03Z, an occasional instance of MVFR flight
conditions cannot be ruled out as light rain exits the terminal. VFR
flight conditions are expected until at least 08Z before the next
round of light rain to light rain showers moves in. Expect MVFR
ceilings to precede and accompany any rain. Gusts increase with
gusts around 30kts midday Tuesday.

&&

.MARINE...
A front is exiting the waters this evening. A stronger system will
arrive Tuesday evening into Wednesday morning and a low pressure
system approaches the waters on Thursday.

Strong, gale force winds will come to an end over the next few
hours. Southwest winds are forecast to be between 20 and 25 mph
overnight and into Tuesday morning, thus a small craft advisory will
be in effect over the coastal waters during this timeframe. There is
high confidence in gale force winds returning Tuesday afternoon and
persisting into Wednesday morning.

Seas will largely subside to 10 to 12 feet tonight and much of
Tuesday. Seas will build again Tuesday evening to 15 to 19 feet and
this will continue into Wednesday. Seas subside to 10 to 13 feet
Wednesday evening.

&&

.HYDROLOGY...
Rain will ease tonight into Tuesday before another front
reaches the area later Tuesday into Wednesday increasing
precipitation rates. Cooler air moving into the area Tuesday night
adds some uncertainty to the river levels. Current forecasts
have snow levels dropping to 2000 to 2500 feet by Wednesday
morning. The front Tuesday night into Wednesday has more
moisture than the todays system but the cooler air will keep
some of the moisture in the mountains in the form of snow. This
combination makes for tricky river forecasting.

Rivers continue to rise this afternoon. Rivers that continue to
stay above flood stage will rise even further above. This first
round will drive a few rivers above flood stage (with a few
already above flood). The second round of precipitation will
drive additional rivers above flood stage with major flooding
possible along the Skagit and moderate flooding for the river
flowing out of the Central Cascades like the Skykomish,
Snoqualmie and Snohomish. The Skokomish could also reach
moderate flood stage.

A flood watch is in effect through Thursday afternoon across the
lowlands.

With a couple more rounds of precipitation the landslide threat will
remain very elevated through Thursday. Felton/HPR/JBB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...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-Island County-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-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 from 4 PM Tuesday to 10 AM PST Wednesday for
     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-Port Townsend Area-San Juan County-
     Shoreline / Lynnwood / South Everett Area-Southern Hood
     Canal-Western Strait of Juan de Fuca-Willapa and Black
     Hills.

     Flood Watch through Thursday 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-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-
     Shoreline / Lynnwood / South Everett Area-Southern Hood
     Canal-Western Strait of Juan de Fuca-Willapa and Black
     Hills.

     Winter Storm Warning from 4 PM Tuesday to 10 PM PST Wednesday
     for Cascades of Snohomish and Northern King Counties-
     Cascades of Whatcom and Skagit Counties.

     Winter Weather Advisory from 4 PM Tuesday to 10 PM PST
     Wednesday for Cascades of Pierce and Lewis Counties-
     Cascades of Southern King County-Olympics.

PZ...Small Craft Advisory until 10 AM PST Tuesday for Grays Harbor
     Bar.

     Gale Warning until 6 PM PST this evening for Admiralty Inlet-
     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-
     Northern Inland Waters Including The San Juan Islands-
     Puget Sound and Hood Canal-West Entrance U.S. Waters
     Strait Of Juan De Fuca.

     Small Craft Advisory from 6 PM this evening to noon PST
     Tuesday 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 Watch from Tuesday afternoon through Wednesday morning
     for Central U.S. Waters Strait Of Juan De Fuca-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 1 AM PST Tuesday for Central U.S. Waters
     Strait Of Juan De Fuca-East Entrance U.S. Waters Strait
     Of Juan De Fuca.

     Gale Watch from Tuesday evening through Wednesday 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.

&&

$$