Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
990
FXUS66 KSEW 142357
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
357 PM PST Sun Dec 14 2025
.SYNOPSIS...
Another atmospheric river will bring several rounds of
precipitation across the region this week. The first system will
arrive tonight through Monday, with rain and gusty southwest
winds. Another system Tuesday into Wednesday will bring in
slightly cooler air, and accumulating mountain snow. The
unsettled weather will continue through the end of the week.
The threat of river flooding is expected to continue through the
week with the additional precipitation.
&&
.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
An area of showers were moving north into Victoria/Whatcom and
Skagit counties this afternoon with a weak surface trough,warm
front. Amounts from this round again are expected to be light,
with just several hundredths of an inch. The rest of western WA
remains overcast through the afternoon, with most temperatures
in the lowlands in the mid 50s (average for this time of year is
around 47).
The atmospheric river pattern remains in place across the
Pacific Northwest. A strong 300 mb jet continues to transport
moisture into the region, with the nose of this jet expected to
remain along the WA coast through much of the week. A frontal
system with this synoptic setup will swing through the region
tonight into Monday. This first system is expected to be the
warmest of the systems passing through this week, with snow
levels hovering around 8,000 to 9,000 ft. The rain will arrive
late this evening into Monday, with the hi-res guidance showing
more of a convective type mode with the showers. There is also a
20-30% chance of thunder (especially along the coast), which may
produce locally heavier amounts (up to 0.25-0.50"/hr). The rain
with this round will wrap up Monday evening. All set and done,
this round of rain is expected to 0.50-1" of rain in the
lowlands, 1-2" along the coast, and 2-3" in the mountains with
potential for locally higher amounts exceeding 4". This will
cause additional rises in streams and rives (see hydrology
section for more details). In addition to rain, a wind advisory
continues from tonight through tomorrow evening for breezy
southwest winds of 25 to 30 with gusts to 45 to 55 mph. The
highest wind gusts are expected along the Pacific coast,
although the threat remains nil at the present time for seeing
wind gusts exceed 60 mph (high wind warning threshold).
Another system with this atmospheric river will arrive Tuesday
into Wednesday. This system will be cooler, as snow levels drop
Tuesday night into Wednesday down to around 2,000 ft. The
trickiest part of the forecast is determining how quickly the
snow levels will drop. Models show more of a delay in the drop
of the snow level (occurring Tuesday night/Wednesday morning).
The warm air mass may cut into the snow accumulations, and this
may delay the cold winds behind the cold front bringing the snow
levels down. There is still a 50% chance that Snoqualmie Pass
could see over 12" of snow through Wednesday evening (and it`s a
90% chance for Stevens Pass). QPF in the lowlands varies quite a
bit, but the mean NBM guidance gives a 48 hour total through
Wednesday night of just over an inch in the Puget
Sound/Northwest Interior, to 1.6" in the south interior.
Continue to monitor the forecast as confidence increases on
potential impacts with this system.
Additionally, waves are expected to increase along the coast
at times Monday through Wednesday, with waves approaching 15 to
17 ft. While the periods will likely carry some of the energy
to the coast, the combination of the waves heights and periods
fall short of criteria for issuing a high surf advisory at this
time.
High temperatures will remain above average through Tuesday,
with highs remaining in the mid to upper 50s.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
The Tuesday system continues into Wednesday with precipitation
decreasing Wednesday evening. A third system appears likely
Thursday into Friday, with a similar amount of precipitation to
the previous two systems. The temperatures will cool to around
average with highs in the mid to upper 40s (lows dipping into
the mid and upper 30s). Ensembles favor a more active weather
pattern continuing into next week (although some splits in
solutions).
HPR
&&
.AVIATION...
Southwest to west-southwest winds aloft persist the entire TAF
period and are expected to increase in strength after 12Z Monday.
Light rain will gradually come to an end across far northwestern
Washington/KBLI after 23Z. Low to mid-level cloud cover will persist
through the entire TAF period. After 05Z, a front will approach from
the west and bring gusty winds, rain, and MVFR to IFR flight
conditions to all terminal]ls.
Gusty 15kt to 25kt southerly winds are expected as the front begins
to approach, beginning between 05Z-09Z Monday at most terminals.
There is high confidence (90% chance or greater) in gusts of 25kts-
35kts after 11Z Monday. However, gusts of 40kts cannot be completely
ruled out.
KSEA... MVFR ceilings have lingered longer than previously
anticipated and are now expected to be around until at least 03Z.
The most likely timeframe of VFR ceilings is between 03Z-06Z. Light
rain is forecast to begin as a front approaches the terminal after
08Z with associated MVFR ceilings. Southerly winds increase with
gusts around 25kts after 10Z. Confidence has increased to 50%-60%
that gusts around 35kts will begin after 15Z-16Z and persist through
the remainder of the TAF period. Gusts of 40kts cannot be completely
ruled out during this time frame.
&&
.MARINE...
A front traverses across the coastal waters and seas late tonight
(Sunday) through Monday and bring strong winds. A Gale Warning is in
effect for the coastal waters, the west entrance Strait of Juan de
Fuca and the corridor extending from Puget Sound/Hood Canal north
through the northern Salish Sea. Probabilities of the gale force
winds are now 70%-80% across Puget Sound/Hood Canal through the
northern Salish Sea. As for the coastal waters, probabilities of
gale force winds are above 90%. Seas will also build to 18-20ft
beginning late tonight through at Monday and remain elevated through
the week, especially as another weather system moves through on
Wednesday.
&&
.HYDROLOGY...
Most rivers will continue to recede through tonight. Atmospheric
river arriving Monday morning with rivers rising again by late
morning. Even with the rises most of the rivers staying below
flood stage Monday. Rivers going 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 Monday night into Tuesday before the tail end of the
atmospheric river 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 lower reaches of the Snoqualmie.
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. There
is more moisture with this second surge of the atmospheric
river 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 from Monday morning through Thursday
afternoon across the lowlands. Felton
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Wind Advisory from 10 PM this evening to 10 PM PST Monday 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.
Flood Watch from Monday 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.
PZ...Gale Warning from 10 PM this evening to 4 PM PST Monday 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-East Entrance U.S. Waters Strait Of
Juan De Fuca-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 until 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.
&&
$$
NWS SEW Office Area Forecast Discussion