368
FXUS66 KSEW 162351
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
351 PM PST Tue Dec 16 2025

.SYNOPSIS...
A period of very active weather will dominate the week
ahead as a series of frontal systems produce cascading impacts
across Western Washington. In addition to ongoing river flood
concerns, another period of windy conditions is expected
tonight into early Wednesday. Snow levels will tumble to the
passes by early Wednesday with blizzard conditions expected in
the mountains. Cool, unsettled conditions will remain in place
through the remainder of the week with substantial additional
snowfall in the mountains.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...
A brief lull this morning will be short and sweet, with a
secondary, stronger system arriving later this evening and
overnight, bringing mountain snow, lowland rain, and breezy
conditions through much of the area. Active weather looks to
continue throughout the short term, with the hazards listed down
below.

The following key messages with this secondary system and week
ahead are outlined below.


* RAIN: With this secondary system, we will see rain amounts
  generally in the mountains around 1 to 3 inches, with an inch
  or less in the lowlands through Wednesday evening. Initially
  this evening, the snow levels will remain high, generally
  around 8000 to 9000 feet, which will keep the landslide risk
  elevated. There is also a very slight chance of an isolated
  thunderstorm or two developing Wednesday morning, but the
  likelihood of any thunderstorm remains low. For more
  information regarding hydrology and river flooding, please
  refer to the .HYDROLOGY section down below.

* SNOW: This secondary system moving later this evening will
  have snow levels initially start at 8000 to 9000 feet, slowly
  lowering them, especially after midnight, down to 2000 to 2500
  feet. Ample moisture from this system will result in
  significant mountain snowfall for the Cascades and Olympics.
  Snow will be heavy at times along with breezy winds up to 45
  mph, therefore, a Blizzard Warning has been issued for late
  tonight into Wednesday afternoon. We could see totals around
  10 to 15 inches at Snoqualmie Pass, with 15 to 20 inches at
  Stevens, and upwards to 2 to 3 feet at Mount Baker and Mount
  Rainier. A convergence zone will set up over the Cascades
  which could locally drive amounts up further. With upslope
  flow and additional systems, snow will continue at the
  mountains through Thursday, with additional winter headlines
  likely needed for the Cascades.

* WINDS: Winds will continue to increase this afternoon and evening,
  with widespread gusts up to 50-55 mph along the coast and up to 40-
  45 mph across the interior. Southwesterly winds this afternoon
  will shift west to northwesterly later this evening, with the
  highest gusts later tonight through the Strait of Juan de Fuca and
  inland into western Snohomish County. The breezy winds, combined
  with deeply saturated soils, raises the risk of downed trees and
  localized power outages.

* COASTAL HAZARDS: Minor coastal flooding remains possible along
  the San Juan County island coastlines during Wednesday`s high
  astronomical tide. The threat of minor coastal flooding shifts
  to along the Pacific Coast on Thursday and Friday. Seas will
  also build along the Pacific Coast Wednesday morning,
  generating large breaking waves that may pose a danger to
  beachgoers and cause localized coastal erosion.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Active weather looks to continue throughout the long term, with
a series of systems arriving throughout the weekend and into the
first half of next week. Lowland rain and mountain snow will
continue as snow levels remain near or just below pass levels.
Cool and unsettled conditions will remain.

Mazurkiewicz

&&

.AVIATION...
A strong frontal system with an atmospheric river will
continue to impact terminals rest of today into Wednesday. Moderate
to heavy precipitation continues to move across the central and
northern terminals. Visibilities and/or ceilings have dropped to IFR
with this activity. There is a 15-20% chance of thunder along the
coast/south interior terminals rest of today into Wednesday (tops
are expected to be low with CB`s less than 20,000-25,000 ft.). The
precipitation will continue in the region tonight into Wednesday.
Strong SW winds will continue to increase with gusts up to 35 to 45
kt in most terminals tonight/Wednesday morning. Strong NW outflow
through the Strait of Juan de Fuca may result in a shift of winds to
the NW in and around KPAE (wind shear is possible with this push).
In addition, snow levels will drop to around 2,000 with blizzard
conditions in the Cascades & Olympics through late Wednesday
morning. Outside of areas of precipitation, MVFR ceilings are likely
tonight, with a gradual lift up to VFR Wednesday morning before
dropping back down to MVFR in the afternoon.

KSEA...Complex of moderate to heavy rain is moving over the terminal
as of 22Z (reducing visibilities/ceilings down to MVFR/IFR).
Additional bands of moderate to heavy precip will move through the
terminal through 12Z. Outside of the precipitation, ceilings will
drop to MVFR through the evening into Wednesday morning, then
improve to VFR/overcast early Wednesday morning, before dropping
back to MVFR in the afternoon. A few showers will be possible late
Wednesday morning into the afternoon. Strong SW winds will increase
to 10-20 kt with gusts to 30-40 kt possible overnight (strongest
gusts expected between 06Z and 12Z tonight. Winds decrease back down
to 10-15 kt gusting to 25 kt later in the morning/afternoon.

HPR

&&

.MARINE...
A strong frontal system will continue to cross the Pacific Northwest
late tonight into early Wednesday, bringing elevated winds and seas
to the region. Gale force winds will cover all area waters by this
evening, with the strongest winds through the central and eastern
Strait of Juan de Fuca early Wednesday morning reaching storm force.
Winds will remain elevated but will gradually ease into Wednesday
afternoon with SCA winds continuing over the coastal waters and
through the Strait of Juan de Fuca. A low pressure system will cross
the region on Thursday, keeping small craft advisory winds across
the coastal waters.

Seas around 11 to 14 feet will continue to build to 15 to 21 feet by
early Wednesday morning. Seas will gradually subside to 10 to 14
feet by Thursday, where they will remain through Friday. Seas will
subside to below 10 feet over the weekend.

15

&&

.HYDROLOGY...Major flooding is possible on the Skagit river
beginning Wednesday morning in the upper reaches with the flood
crest reaching Mount Vernon Wednesday night. Several other
rivers are forecast to reach minor to moderate flood but there
is a fair amount of uncertainty with the crests, especially due
to how quickly and and how low the snow level gets.

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

The landslide threat remains very elevated will continue to be high
through at least tomorrow.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Wind Advisory from 4 PM this afternoon to 6 AM PST Wednesday
     for City of Seattle-Eastern Kitsap County-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 the North Cascades-
     Lowlands of Western Whatcom County-San Juan County-
     Shoreline / Lynnwood / South Everett Area.

     Coastal Flood Advisory from 2 AM to 8 AM PST Wednesday for San
     Juan County.

     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-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-
     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-Olympia and
     Southern Puget Sound-Olympics-Shoreline / Lynnwood /
     South Everett Area-Willapa and Black Hills.

     Blizzard Warning from 2 AM to noon PST Wednesday 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-Olympics.

     Winter Storm Warning from 4 PM this afternoon to 10 PM PST
     Wednesday for Cascades of Pierce and Lewis Counties-
     Cascades of Southern King County-Olympics.

     High Wind Warning from 4 PM this afternoon to 6 AM PST
     Wednesday for Downtown Everett / Marysville Area-Eastern
     Strait of Juan de Fuca-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 Pierce and Southern
     King Counties-Lowlands of Western Skagit and Northwestern
     Snohomish Counties-Middle Chehalis River Valley-Northern
     Hood Canal-Northern Washington Coast-Olympia and Southern
     Puget Sound-Port Townsend Area-Southern Hood Canal-
     Western Strait of Juan de Fuca.

     High Surf Advisory from 1 AM to 10 AM PST Wednesday for Grays
     Harbor County Coast-Northern Washington Coast.

PZ...Small Craft Advisory until 4 PM PST Wednesday for Grays Harbor
     Bar.

     Gale Warning until noon PST Wednesday 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 from 4 PM this afternoon to midnight PST tonight
     for Central U.S. Waters Strait Of Juan De Fuca-East
     Entrance U.S. Waters Strait Of Juan De Fuca.

     Storm Warning from midnight tonight to 6 AM PST Wednesday for
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance
     U.S. Waters Strait Of Juan De Fuca.

     Gale Warning from 6 PM this evening to 6 AM PST Wednesday for
     Admiralty Inlet-Northern Inland Waters Including The San
     Juan Islands-Puget Sound and Hood Canal.

&&

$$