Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
840
FXUS66 KSEW 091023
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
323 AM PDT Mon Mar 9 2026
.SYNOPSIS...
Upper level trough over Western Washington keeping cool
unsettled weather over the area through tonight. Next system
arriving Tuesday. A much stronger system arrives Wednesday and
Wednesday night bringing heavy snow to the mountains and rain
and locally windy conditions to the lowlands. The wet weather
pattern will remain intact into the weekend.
&&
.SHORT TERM /TODAY THROUGH WEDNESDAY/...
Satellite imagery and doppler radar shows convergence zone along
the King/Snohomish county line extending into the Cascades along
Highway 2. Scattered showers over the remainder of the area
except in the Central Puget Sound where skies are mostly cloudy.
Temperatures at 3 am/10z were in the mid 30s to lower 40s.
Scattered showers continuing this morning. Surface gradients are
onshore and the 925 mb winds are west southwesterly at 10 to 20
knots. This will keep the snow level above sea level,
at approximately 500 feet, this morning. Snow falling in the
convergence zone from about Skykomish eastward ( the Skykomish
airport webcam has snow on the ground at this hour ). The
convergence zone will remain intact for a few more hours this
morning then dissipate. Stevens Pass has already gotten around
8 inches of new snow overnight with another 6 to 8 inches
possible today. Lesser amounts in the mountains outside of the
convergence zone. Scattered showers continuing this afternoon
with the snow levels rising with the daytime heating. The
daytime heating will destabilize the air mass somewhat this
afternoon creating a slight chance of a thunderstorm. Highs will
be cool, in the mid 40s.
Scattered showers continuing this evening. Shower activity
decreasing overnight as a weak upper level ridge moves in ahead
of the next frontal system. Another convergence zone possible
over Skagit or Snohomish county moving into the Cascades
overnight. Heaviest snowfall in the mountains with the
convergence. Another 7 to 9 inches possible. Outside of the
convergence new snow amounts mostly in the two to five inch
range. Lows Tuesday morning in the upper 20s to mid 30s.
Snow levels will be near the surface Tuesday morning but shower
activity will be minimal. Rain out ahead of the next system
reaching the coast in the afternoon spreading inland late in the
day. Highs again in the mid 40s.
Rain over the entire area Tuesday night into Wednesday. Snow
heavy at times in the mountains. Snow levels between 1000 and
1500 feet Tuesday night rising to 2000 to 3500 feet Wednesday.
This will be the beginning of prolonged period of significant
snows in the mountains. Lows in the mid 30s to lower 40s. Highs
in the lower 50s.
Winter storm warning remaining in effect until 5 am Tuesday for
the Cascades from North King county northward. An additional 8
to 16 inches of new snow possible with the higher amounts near
Stevens Pass.
Winter weather advisory in effect for the remainder of the
Cascades through Tuesday afternoon for the possibility of 6 to
10 inches of new snow.
A winter weather advisory remains in effect for the Western
Strait of Juan de fuca for possible 1 to 4 inch snow
accumulations in the Lake Crescent area and along Highway 101
heading towards the north coast.
A winter weather advisory is also in effect for the foothills
and valleys of Snohomish and Northern King county with the
convergence zones producing up to six inches of new snow through
Tuesday morning.
A winter storm watch remains in effect for the Cascades and
Olympics from later Tuesday into Friday for another 2 to 4 feet
of new snow possible. Blizzard conditions are also possible
later Wednesday into Wednesday night. Felton
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
System moving through Wednesday night with a strong winds
possible along the coast and Strait of Juan de Fuca into Whidbey
Island. Windy conditions elsewhere. Its possible a blizzard
warning may be needed for the Cascades.
Potential atmospheric river arriving Thursday with the river
aimed at Western Washington at least through Friday. Snow levels
will rise but not too much, into the 3500-4500 foot range. New
snow totals will be measured in feet not inches.
Models in fairly good agreement that a weak upper level ridge
will build offshore cutting the atmospheric river off and
pushing the system south of the area Saturday. The break in the
precipitation will be short lived with another front approaching
Sunday.
Extended models beyond day 7 are in good agreement with another
atmospheric river reaching the west coast Monday into Tuesday.
Some solutions have this feature north of the area and some have
it right over Western Washington. Heavy snow in the mountains
and rain in the lowlands followed by a warm heavy rain is a
scenario where the rivers will need watching. Felton
&&
.AVIATION...
Zonal flow aloft through the TAF period. Post-frontal onshore flow
persists at the surface. VFR across most terminals so far this
morning. Puget Sound terminals (KBFI, KPAE, KSEA) may continue to
see instances of MVFR cigs due to convergence zone activity meander
across King/Snohomish counties before petering out around 15z.
Mostly VFR into the day on Monday as well but can`t rule out
intermittent low cigs/vis from passing showers. A convergence zones
looks to redevelop again between 22z Monday and 00z Tuesday, likely
bringing MVFR cigs to KPAE again. Breezy S/SW winds increasing
during the afternoon to 20-30 kt then decreasing after 00z.
KSEA...
A mix of VFR/MVFR cigs due to a convergence zone until 15-18z.
Afterwards, mainly VFR throughout the rest of the day aside from
brief low cigs/vis from passing showers. S/SW winds this morning
between 8-10 kt, increasing Monday afternoon with gusts up to 25 to
30 kt possible. Gusts decrease around 00-02z Tuesday. NBM shows 40-
50% chance of MVFR cigs redeveloping after 00z Tuesday as due to
convergence zone activity reemerging. A mix of VFR/MVFR again into
Tuesday morning.
McMillian
&&
.MARINE...
Mostly onshore flow through midweek and likely strong at times. This
has resulted in SCA being in effect through the Strait of Juan de
Fuca. West winds will also remain elevated for the Coastal Waters
before easing briefly by Monday night. A stronger weather system
will move across the waters Wednesday into Thursday, resulting in
additional headlines. Confidence is increasing in gale force winds
on Wednesday for the Coastal Waters, with the probability of gales
wind gusts ranging between 50 to 70% for the interior waters on
Wednesday. Winds will remain elevated, but slowly ease Thursday into
late week.
Seas will range 9 to 12 feet through Tuesday. Seas will then build
Wednesday to 14 to 17 ft over the Coastal Waters before falling
between 10 ft by Thursday morning and remain that way through the
remainder of the week.
McMillian
&&
.HYDROLOGY...
Heavy precipitation, combined with rising snow levels,
will bring increased flows on the Skokomish River beginning
later Tuesday. It will be a tough call on the Skokomish River
with snow levels only rising to around 3500 feet. The current
river forecast has the Skokomish going over flood stage
Wednesday. Elsewhere, river levels will rise, however,
additional river flooding is not expected over the next seven
days. Felton
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Storm Warning until 5 AM PDT Tuesday for Cascades of
Snohomish and Northern King Counties-Cascades of Whatcom
and Skagit Counties.
Winter Storm Watch from late Tuesday night through Friday
morning 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.
Winter Weather Advisory until 5 PM PDT Tuesday for Cascades of
Pierce and Lewis Counties-Cascades of Southern King
County.
Winter Weather Advisory until 11 AM PDT Tuesday for Foothills
and Valleys of Snohomish and Northern King Counties.
Winter Weather Advisory until 11 AM PDT Tuesday for Lake
Crescent Area Including US 101-Western Strait of Juan de
Fuca.
Winter Storm Watch from Tuesday afternoon through Friday
morning for Olympics.
PZ...Small Craft Advisory until 5 PM PDT this afternoon for Grays
Harbor Bar.
Small Craft Advisory until 11 AM PDT this morning for Central
U.S. Waters Strait Of Juan De Fuca-East Entrance U.S.
Waters Strait Of Juan De Fuca.
Small Craft Advisory until 5 PM PDT 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.
&&
$$
NWS SEW Office Area Forecast Discussion