Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
860
FXUS66 KSEW 131112
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
412 AM PDT Fri Mar 13 2026
.SYNOPSIS...
Lowland stratiform rain and heavy mountain snow expected to
continue today. However, a colder air mass will keep the chance
of a rain/snow mix for central Puget Sound through this
morning. Conditions expected to remain unsettled this weekend
and into next week as an upper level ridge builds over the
region, bringing milder temperatures.
&&
.SHORT TERM /TODAY THROUGH SUNDAY/...
Latest observations show some locations across the lowlands getting
light snow or rain/snow mix early this morning. A cooler air
mass over the region will have snow levels down to 300-1000 ft
early this morning, before rising above 1000 ft late this
morning. High uncertainty still remains on snow accumulation for
the lowlands. Accumulations will be highly dependent on
location, surface and ground temperatures, and where the highest
precipitation rates set up. In addition, surface temperatures
are expected to remain just above freezing through the morning,
leading to highly variable accumulations if there are any. So
far light snow has been observed at locations where the
temperature has decreased to around 34 degrees or lower, while
locations hovering at 36 degrees have just seen rain. There is
moderate to high confidence that central Puget Sound may see
some snow or rain/snow mix. Expect these wintery conditions to
continue through 10 AM. If any snow does accumulate, it will
likely be grassy surfaces, elevated surfaces, and the foothills.
A stalled frontal boundary in Oregon associated with higher
snow levels will drift northwards at times fluctuating snow
levels between 1000-3000 ft along the southern interior. These
higher snow levels will keep the precipitation type as rain in
this area. With the boundary stalled to the south, expect
moderate to heavy rain in the southern interior.
Heavy snow will also continue across the Olympics and Cascades
through early Saturday morning and will taper off into the weekend.
A Winter Storm Warning continues for the mountains. Expect to see an
additional 1 to 3 feet of snow for the Cascades passes and 1 to 6
inches for the Olympics.
On Saturday, the frontal boundary finally moves southward and away
from Western Washington. Slightly colder air will move into the
region, dropping snow levels across the lowlands to 200 to 800 ft
Friday night into Saturday morning. This will bring another chance
for snow. However, this time there will be limited moisture and will
be more showery in nature. Confidence on snow accumulation remains
low at this time and again will be highly dependent on where the
snow showers develop and precipitation rates.
An upper level ridge will build over Western Washington late
Saturday night, drying out conditions briefly before a weak
atmospheric river moving into British Columbia clips the region.
Snow levels will start out low Sunday morning around 300-1000 ft,
but will increase throughout the day as warmer air moves into the
region.
MGF
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Snow levels are expected to rise to 5000-8000 ft by late Sunday into
early Monday morning and will hover around around these values into
next week as well. This will result in a snow to rain transition on
late Sunday into early Monday. As a result, mountain snow will be
limited to the highest peaks.
The previously mentioned upper level ridge will continue over
Western Washington and will bring milder temperatures to the region.
A gradual warm up is expected throughout next week. Temperatures
early next week will be in the 50s and by midweek will be peaking in
the upper 50s to low 60s. Additionally, multiple weak atmospheric
rivers will ride along the ridge keeping conditions wet and
unsettled.
MGF
&&
.AVIATION...
Westerly flow aloft will continue through the TAF period as a
strong upper level jet remains over western Washington today.
Precipitation will continue across the region, though will
gradually shift southwards throughout the day. A mixed bag of
conditions continues out there early this morning, though the
majority of the terminals are trending MVFR to IFR and are
either seeing snow falling or a rain/snow mix. While snowfall
accumulations are expected to be limited, if rates remain heavy,
minor snow accumulations can be expected on paved surfaces,
including snow sticking onto airport surfaces through the early
morning hours.
Expect lower ceilings and visibilities to hang on through the
morning hours with abundant surface moisture and light low level
flow. Conditions may further lower to LIFR in any areas of heavier
precipitation. Expect some improvement for northern terminals
by mid-morning, though expect cigs to remain MVFR/IFR for the
majority of terminals through this afternoon. Winds remain light
and variable at primarily 6 kt or less.
KSEA...Conditions at the terminal are IFR with light snow
falling this morning. Snow may stick to airport surfaces if
snowfall rates remain heavy enough, particularly between 10-
16Z. Otherwise, any lingering precipitation will likely
transition back to rain between 16-18Z. IFR ceilings and
visibilities will continue at the terminal through the morning
hours and could drop to LIFR in any heavier precipitation.
Expect ceilings to slowly improve to low-end MVFR by late
afternoon. Winds are light out of the E/NE at 6 kts or less this
morning and will become more S/SE by the afternoon.
14
&&
.MARINE...
A stationary front will remain over the southern portion of the
coastal waters today, before moving south out of the area on
Saturday as high pressure builds into the coastal waters. Winds
and seas have come down below advisory criteria, with both expected
to remain below criteria throughout the day. Northerly winds will
then increase across the coastal waters overnight into Saturday,
with probabilistic guidance indicating roughly a 60-80 percent
chance of gusts approaching small craft. Seas will hover between
6-9 ft through Saturday, before subsiding towards 4-6 ft on
Sunday. A warm front will then brush the outer coastal waters on
Monday, potentially bringing gusty southerly winds to the coastal
waters and portions of the interior waters. Seas will then build
towards 10-13 ft and hover at this range through midweek. The
trailing cold front looks to approach the area waters mid to
late week.
14
&&
.HYDROLOGY...
The Skokomish River has fallen below flood stage and is
expected to continue to recede over the next few days. While
precipitation will continue throughout the day today, snow
levels hovering between 1000-2500 ft around Mason County should
mitigate any additional flood risk on the Skokomish today.
There does, however, remain a threat of flooding for rivers
across the Southwest Interior today and into the weekend with
the heaviest precipitation expected to remain over the area
today. This, combined with higher snow levels, may bring
flooding to rivers in the Chehalis Basin including but not
limited to the Skookumchuck, Newaukum and the Chehalis River
from Grand Mound to Grays Harbor. Therefore, a Flood Watch
remains in effect for these areas.
The threat for flooding will briefly ease on Sunday before an
atmospheric river is expected to move inland to the north early
next week. This could bring additional flooding concerns to
portions of the area- with rivers over the northern portion of
the area bearing watching through the first part of the week.
14
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Storm Warning until 5 AM PDT Saturday 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.
Flood Watch through Sunday afternoon for Cascades of Pierce
and Lewis Counties-Foothills and Valleys of Thurston and
Lewis Counties-Foothills of the Western and Southern
Olympic Peninsula-Grays Harbor County Coast-Lower
Chehalis River Valley-Lowlands of Lewis and Southern
Thurston Counties-Middle Chehalis River Valley-Olympia
and Southern Puget Sound-Olympics-Willapa and Black Hills.
PZ...None.
&&
$$
NWS SEW Office Area Forecast Discussion