Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
599
FXUS66 KSEW 132323
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
323 PM PST Sat Dec 13 2025
.SYNOPSIS...
River flooding continues across areas of western Washington.
Drier conditions will persist through tonight, before a weak
front crosses the region early Sunday. A stronger system will
follow Monday into Tuesday, bringing heavier precipitation and
strong winds for some areas. A deeper trough will bring cooler
air and the potential for heavy mountain snow Tuesday night into
Wednesday. Conditions remain unsettled heading into late week
with additional rounds of lowland rain and mountain snow
expected.
&&
.SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...
Most areas of fog have scattered across the region this
afternoon with latest satellite imagery showing high cloud
cover streaming in overhead. Conditions will generally remain
dry across the region through tonight with high pressure
situated over the region.
The break in the weather will remain short-lived, however, as
the ridge flattens into Sunday and the next weak frontal system
approaches western Washington. Rain will move inland by early
Sunday, but expect overall amounts to remain rather light, with
most areas only expected to receive a few hundredths to a tenth
of an inch across the interior and a few tenths along the coast.
Snow levels will remain rather high- generally between 6000-8000
ft - so rainfall amounts in the mountains are generally expected
to range from a quarter of an inch to an inch in spots, but are
not expected to bring additional impacts at this time.
14
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Models remain consistent with regards to next atmospheric river
system getting into full swing early Monday morning and bringing
another round of significant rainfall throughout the day. QPF
amounts with this particular system are lower than with the
prior AR with lowland rainfall amounts generally in the half-
inch to three- quarters of an inch. The problem arises when
considering the impacts this new rainfall may have on already
existing conditions from prior AR. Needless to say, flooding due
to already elevated river levels and landslides due to already
saturated ground top that list. However, this is both not as bad
as it appears to be and just as bad as it appears to be. To
cover the first part of that statement, precip amounts favor
falling mostly in the first half of the day, tapering off in the
afternoon and evening...even though PoPs throughout the day
remain high. Making the situation as bad as it appears, or
perhaps worse, is the follow-up frontal system Tuesday, drawing
in a much more significant slug of moisture into the area. This
will result in lowland rainfall amounts of 0.75 inches on the
low end and as high as 1.50 inches on the high end. The
cumulative effects of Monday and Tuesday will certainly compound
already existing issues over the area. Lastly, winds during the
day on Monday will be elevated with most locations in the CWA
becoming breezy to locally windy. Locations more prone to higher
wind speeds, especially along the coast, the San Juans and the
NW interior may see winds approach wind advisory criteria, but
that risk will need to be evaluated once this system enters the
near term time frame.
Switching gears to higher elevations, snow levels remain high Monday
before starting to lower Monday night and into Tuesday. With the
aforementioned incoming moisture for Tuesday, accumulating snowfall
will be an issue as snow levels by Tuesday night will dip down to
pass level. Winter weather headlines may be needed if guidance
remains consistent.
Wednesday brings a weak ridge, but unfortunately is not strong
enough scour all of the moisture out of the area. As such, this will
keep at least showers in the forecast...even though, thankfully, QPF
values remain low during this time. A broad upper level trough over
the northwestern Canadian coast will keep weather over W WA active
for the remainder of the forecast period, continuing to cycle
moisture into the area and keeping the latter end of the forecast
wet.
18
&&
.AVIATION...
Southwesterly flow aloft as an upper ridge axis gradually shifts
to the east. Winds will remain light near the surface at all
terminals this afternoon. With fog having dissipated, terminals
have mostly rebounded to VFR this afternoon.
A front will approach from the west after 02Z and bring elevated
winds between 10-15kts at KPAE and KHQM. The front is expected
to reach all other terminals between 07-11Z. Winds at the
remaining terminals will generally be less than 8kts with the
front. Rain and associated MVFR flight conditions/ceilings are
expected along and behind the front. Rain is forecast to end at
most terminals by 16Z with lingering reduced flight conditions
possible after rain ends.
KSEA...VFR conditions through tonight. A front will begin to
approach the terminal around 11Z. Light rain will accompany the
front with the greatest chance of MVFR flight conditions between
14Z-16Z Sunday. Winds remain from the south to southeast and
around or less then 6kts the entire TAF period.
&&
.MARINE...
A weak frontal system will cross the waters later today
through early Sunday, generating SCA winds and seas above 10 feet
across the far northern coastal waters. Seas will remain between 6
to 9 feet elsewhere.
A stronger system will arrive late Sunday night into Monday, which
will bring stronger winds to the outer waters that will likely reach
Gale force. This system will also bring larger swells to the region,
with waves reaching 15 to 20 feet early next week.
Seas will remain elevated throughout the rest of next week as
another series of systems crosses the area waters. There will likely
be another round of wind and sea headlines, with winds potentially
reaching Gale force across most area waters mid week.
15
&&
.HYDROLOGY...
Rivers continue to recede this afternoon as western Washington gets
a break from the wet weather. Even the lower reaches of the rivers
will approach or lower below flood stage later today into tonight.
The exceptions to this will be the lower reaches of the Chehalis
river which will not fall below flood stage until Sunday from Porter
down to Grays Harbor, and the lower reaches of the Skagit river
which will recede to near flood stage by Monday morning.
Rivers will be on the rise again later Monday into Tuesday with
another atmospheric river taking aim at Western Washington.
Rainfall amounts to 3 to 5 inches Monday through Wednesday in the
mountains are forecast. Another round of river flooding will occur
with the atmospheric river but at this time, with the Skagit and
Snohomish Rivers forecast to reach major flooding once again by
midweek. A Flood Watch has been issued for much of western
Washington Monday morning through Thursday evening for potential
incoming river flooding, urban flooding, and small stream flooding.
With very wet antecedent soil conditions, the landslide threat
remains high across the region. Potential is also elevated for
debris flows over area burn scars, which continue to be monitored.
The threat of urban flooding will increase again later Monday into
Tuesday. Small stream flooding, as well as areas with poor drainage,
will pose a risk of localized nuisance flooding and ponding on
roadways later Monday into Wednesday.
Felton/15
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...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...Small Craft Advisory until 10 PM PST Sunday 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.
Gale Warning from 10 PM Sunday to 4 PM PST Monday 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