Washington State Forecast Discussion

Western Washington


749
FXUS66 KSEW 231532
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
832 AM PDT Sun Mar 23 2025

.UPDATE...An atmospheric river will continue to bring heavier
precipitation through tonight, especially for the Olympics and
Cascades from King County northwards. Snow levels also continue to
rise this morning, however, moderate to heavy snow will continue
for another couple hours at Stevens Pass before transitioning to
rain. Otherwise, our friends at the Northwest Avalanche Center
have an Avalanche Warning up for the Cascades. In addition, breezy
winds are expected today, with gusts generally ranging 20 to 40
MPH, and near 45 MPH around Everett and Admiralty Inlet. No major
forecast updates this morning.

&&

.SYNOPSIS...An atmospheric river will bring heavier precipitation,
rising snow levels, and breezy winds through Monday. Upper level
ridge building Monday night into Tuesday with record high
temperatures likely Tuesday. Upper level low offshore Wednesday
will bring the potential for showers and thunderstorms. The low
will remain offshore with unsettled weather Thursday and Friday. A
weak upper level ridge will try and build Saturday.

&&

.SHORT TERM /TODAY THROUGH TUESDAY/...Satellite imagery shows
cloudy skies over Western Washington early this morning.
Precipitation echoes on the doppler radar starting to fill in
across the area with a warm front in place. Temperatures at 3
am/10z were in the lower to mid 40s.

Pluviophiles are going to love the next couple of days. Warm
front over Western Washington today with an atmospheric river
moving inland over Vancouver Island. Not raining in a few areas
early this morning but by sunrise rain over the entire area. Snow
levels near 4000 feet rising to at least 6000 feet this
afternoon. Could see up to 6 inches of new snow in the North
Cascades this morning before the increasing snow levels. Will stay
with the winter weather advisory for this area until 11 am. Highs
will be in the lower to mid 50s.

Atmospheric river right over Western Washington tonight.
Forecasted IVT values in the 700-800 kg/m/seconds. Westerly 850 mb
winds as strong as 50 knots. Snow levels 6500 feet in the North
Cascades and around 7500 feet elsewhere. The heavy rain in the
mountains will create dangerous avalanche conditions. Our friends
at the Northwest Avalanche Center already have a warning up for
the Cascades. In the lowlands, rain along with breezy southerly
winds, 15 to 25 mph with higher gusts. Temperatures will remain
steady overnight with lows in the lower 50s. Record high low
temperatures will be set for many locations.

Atmospheric river remaining over Western Washington Monday. IVT
values lowering to 400 to 500 kg/m/sec. 850 mb winds also easing
to 20 to 35 knots a good indication the atmospheric river will be
weakening. Snow levels well above the pass levels. With more
significant rainfall in the mountains hydrology concerns will be
elevated. See hydrology section for more details. Highs well above
normal, in the mid 50s to lower 60s.

Upper level ridge beginning to build over Western Washington
Monday night pushing what is left of the atmospheric river north
into Southern British Columbia. Even with the rain coming to an
end in some places mostly cloudy skies will keep lows in the mid
40s to lower 50s. More record high low temperatures possible.

Upper level ridge continuing to build Tuesday with just a slight
chance of rain along the coast and near the Canadian border by
afternoon. Record high temperatures have been in the forecast for
the last couple of days. Model trends this morning indicating
highs a couple degrees warmer than the previous forecasts with
lower 70s not only over the Southwest Interior but also in the
Cascade foothills. The GFS ensembles up to a 67 percent chance of
lower 70s in Seattle. ECMWF ensembles not as excited about 70s for
Seattle but have almost all the solutions in the mid to upper
60s. General range for the highs over the entire area 60s and
lower 70s.

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...Extended solutions
remaining consistent on the 00z run with a classic pattern for
convection still in place over Western Washington Wednesday
afternoon and evening. Near record warm air mass in place combined
with a negatively tilted trough approaching from the southwest
in the afternoon will create a very unstable air mass. It is still
too early to go much more than a chance of thunderstorms for
Wednesday afternoon and evening. Negatively tilted troughs have a
habit of slowing down as they approach the area. If the trough
timing is slower than the current model solutions this will push
the convection threat out of the most favorable time frame. Wide
spread on the high temperatures in the ensembles. ECMWF ensembles
already hinting at a slower trough arrival with warmer high
temperatures Wednesday versus Tuesday. GFS ensembles staying with
the idea of convection developing in the afternoon capping high
temperatures in the 60s. Current forecast more in line with GFS.

Negatively tilted trough spinning out of upper level low offshore
moving through Western Washington Wednesday night with showers
and a chance of thunderstorms.

Upper level low remaining off the coast Thursday and Friday with
impulses kicking out of the low moving over the area keeping
showers in the forecast. Snow levels lower back down below the
passes by Friday. High temperatures returning back to near normal,
in the lower to mid 50s.

Upper level low moving off to the northwest Saturday and
weakening. Upper level ridge trying to build over the area ahead
of another negatively tilted trough approaching from the
southwest. Ensembles not indicating much faith in the ridge with
plenty of the solutions indicating light precipitation keeping
showers in the forecast. Felton

&&

.AVIATION...A warm front will continue to lift northward across the
area into this afternoon bringing continued widespread rain and
gusty winds to the area. Increasing westerly flow aloft this morning
with a mixed bag of conditions ranging from MVFR/IFR/LIFR. Expect
overall conditions to worsen, steadily remaining at MVFR/IFR,
heading into the afternoon as precip from the warm front feeds
across the region. Southerly winds will also continue to increase
throughout the later morning hours becoming 10 to 20 kts, with gusts
peaking anywhere from 25 to 35 knots through this evening.
Deteriorated conditions will continue throughout the majority of the
day before subsiding by late tonight.

KSEA...MVFR/IFR ceilings can be expected throughout majority of the
day with continued rain and wind. Southerly winds will ramp up to 12
to 18 kts by the late morning, with gusts peaking around 25 to 35
kts around 19z-00z. With rain and wind, could see lowered
visibilities at the terminal around 3 to 6 SM at times. Conditions
will slowly improve later this evening into Monday morning.

Mazurkiewicz

&&

.MARINE...A frontal system will continue to cross the coastal waters
today, bringing a warm front with increased southerlies to most of
our area waters. Latest guidance indicates stronger southerlies in
the coastal waters, so have upgraded all the coastal water zones to
a Gale Warning. Elsewhere, small craft southerlies can be expected
in the interior waters, with a few gusts up to gale strength
possible in the Eastern Strait and Admiralty Inlet later this
evening. Winds look to subside into Monday as a weak surface ridges
builds into Tuesday for calmer conditions.

Another frontal system looks to enter the area on Wednesday for
additional rounds of elevated winds and seas.

Combined seas this morning around 8 to 11 feet will remain
throughout the weekend. The highest seas (10 to 11 feet) will
likely remain in the outer coastal water zones. Seas look to
decrease below 10 feet early next week, before building back up to
around 12 to 16 feet towards midweek.

Mazurkiewicz

&&

.HYDROLOGY...Heavy rain in the mountains with rising snow levels
the next couple of days. Forecasted rainfall amounts in the next
36 hours in the 4 to 6 inch range over the Olympics with 2 to 4
inches over the Cascades. Snow levels rising to 6000 to 7500
feet. The Skokomish river is likely to go above flood stage
as early as late this afternoon.

This amount of rain combined with the rising snow levels will put
pressure on the remaining rivers in the area. Fortunately with
the rivers relatively low this morning no additional flooding is
forecast Monday into Tuesday. A bunch of the rivers flowing out of
the Central Cascades, including but not limited to the Snoqualmie,
could reach action stage. Will be keeping an eye on the Bogachiel
River as well with the heavy rain in the Olympics. Felton

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory until 11 AM PDT this morning for
Cascades of Snohomish and Northern King Counties-Cascades
of Whatcom and Skagit Counties.

PZ...Small Craft Advisory until 11 PM PDT this evening for Admiralty
Inlet-Central 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 3 PM PDT this afternoon for East
Entrance U.S. Waters Strait Of Juan De Fuca.

Gale Warning until 5 PM PDT this afternoon 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.

Small Craft Advisory from 5 PM this afternoon to 2 AM PDT 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.

&&