Brier Weather Station

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 Latitude N 47° 46' 49"    Longitude W 122° 16' 48"    Elevation 341 ft

096
FXUS66 KSEW 151147
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
346 AM PST Mon Dec 15 2025

.SYNOPSIS...A period of very active weather will dominate the week
ahead as a series of strong frontal systems produce cascading
impacts across Western Washington. In addition to ongoing river
flood concerns, periods of windy conditions are expected today and
again Tuesday night into Wednesday. Snow levels will tumble to the
passes Tuesday night and Wednesday with heavy snowfall 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 /TODAY THROUGH WEDNESDAY/...
Rain is increasing again this morning as a warm front lifts
northward across Western Washington. Moderate to locally heavy rain
and gusty winds will persist through the day before a trailing cold
front sweeps through by early this evening with rain turning to
showers and isolated thunderstorms. Though QPF is lighter with this
system than those of last week, the additional rainfall and high
snow levels will push a number of rivers back into flood flow and
continue the threat of landslides. After a brief lull between
systems Monday night into early Tuesday, a secondary stronger system
arrives later Tuesday. And this one has some worrisome wind
potential with it. When combined with saturated soils already in
place, the threat of fallen trees increases. Models show a sharp
surface mesolow forming to the lee of the Olympics by 09Z Wednesday.
This creates a very strong pressure gradient Seattle southward.
Isallobaric analysis shows impressively strong pressure rises behind
it...as much as 7 or 8 millibars in just three hours early Wednesday
morning. So, it`s not just wind speeds alone, but the rapid manner
in which they could arrive. As such, we have put up a high wind
watch for all of the lowlands Tuesday evening into Wednesday morning
with gusts of 50 to 55 mph possible for the interior lowlands and 60
to 65 along the coast. Snow levels will tumble to the passes late
Tuesday night with significant snowfall expected. Totals could
approach a foot at Snoqualmie Pass by midday Wednesday, 1 to 2 feet
at Stevens, and perhaps 2 to 3 feet at Mount Baker.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
Model consensus keeps the pattern active and unsettled throughout
the extended portion of the forecast. However, the air mass will
remain considerably cooler with snow levels at or below passes into
the weekend. This will allow rivers to recede while snow piles up in
the mountains...a long awaited return to some semblance of normalcy
for December.  27

&&

.AVIATION...A frontal system will move through the area this
afternoon. A stronger system will arrive Tuesday night into
Wednesday with strong winds both aloft and at the surface.
Southwesterly flow aloft through Tuesday.

VFR ceilings with areas of MVFR ceilings and visibilities early this
morning. MVFR conditions becoming widespread by 16z with local IFR
ceilings coast and Kitsap peninsula. Conditions improving to VFR
late afternoon/early evening with mostly VFR conditions into Tuesday
morning.

KSEA...VFR conditions becoming MVFR by 15z. Conditions improving
late afternoon with VFR ceilings tonight. South winds 5 to 10 knots
increasing to 12 to 18 knots with gusts 25 to 30 knots 16z-18z.
Winds  easing to 10 to 15 knots after 06z. Felton

&&

.MARINE...A front will move through the waters today. A stronger
system will arrive Tuesday night into Wednesday morning with another
system Thursday.

Gale force winds today over the waters. Winds easing late this
afternoon into tonight. Small craft advisory winds over the coastal
waters tonight into Tuesday afternoon. Another round of gales for
all the waters later Tuesday into Wednesday morning.
Winds easing Wednesday afternoon.

Seas 14 to 18 feet today subsiding to 10 to 13 feet tonight.
Seas continuing to subside slightly Tuesday before building again to
14 to 18 feet later Tuesday night into Wednesday. Seas subsiding to
9 to 12 feet Wednesday night. Felton

&&

.HYDROLOGY...Most rivers will continue to recede this morning.
Atmospheric river arriving later morning with rivers rising again by
afternoon. Even with the rises most of the rivers staying below
flood stage today. Rivers over flood stage will be the ones that
will have not dropped below much below flood stage over the weekend
like the Skagit, Cedar, White and Cowlitz below Mayfield Dam.

Rain easing tonight into Tuesday before another front reaches the
area later Tuesday into Wednesday increasing precipitation rates.
This second round of precipitation will drive some 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.

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.

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

&&

.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.

     High Wind Watch from Tuesday evening through Wednesday morning
     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 from 10 AM PST this morning 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 Watch from Tuesday evening through Wednesday
     evening 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.

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 from 1 PM this afternoon to 1 AM PST Tuesday for
     Central U.S. Waters Strait Of Juan De Fuca.

     Gale Warning until 1 AM PST Tuesday for 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.

&&

$$

NWS SEW Office Area Forecast Discussion

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