377
FXUS66 KSEW 170936
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
236 AM PDT Mon Mar 17 2025

.SYNOPSIS...Unsettled weather continuing through the rest of the
day. Upper level ridging building briefly on Tuesday will give way
to a break in the wet weather. A series of multiple systems will
move over the region later in the week trough the weekend for
rounds of lowland rain, mountain snow, and breezy winds at times.

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY/...Broad upper level
troughing will continue move over the Pacific Northwest morning.
Weak impulses will gradually move over the region, helping spark
some light shower activity across the area throughout the day,
with snow in the mountains. Snow levels this morning generally
around 1500 to 2000 feet. Recent radar imagery shows just a few
showers across the area this morning.

Onshore flow will also increase today, resulting in a convergence
zone developing across the north/central sound around the early
evening hours. Increased shower activity can be expected in any
heavier banding that develops, along with snow levels being
dragged down lower than 1500-2000 feet. At this time, latest hi-
res guidance suggests that areas in the Cascades, particularly
around Snoqualmie Pass, could receive locally higher snow
accumulations this evening due to the convergence zone placement.

Aforementioned troughing will shift eastward into Tuesday,
allowing for upper level ridging to briefly build into the area.
Drier conditions can be expected on Tuesday with maybe just a pop
up shower or two.

Another system will push through western Washington on Wednesday
with lowland rain, mountain snow, and some breezy winds Snow
levels in the 2000 to 3000 feet during this time. Winds look to be
a touch breezy for areas along the coast and possibly the North
Interior.

.LONG TERM /THURSDAY THROUGH SUNDAY/...The active weather pattern
continues as a stream of systems continues to move through our
area. Lowland rain and more mountain snow will return on Thursday
as a system passes through the area, with another system moving
through on Friday for the same result. The system on Friday
definitely looks a bit wetter than the other ones, with unsettled
weather continuing through the weekend.

Mazurkiewicz

&&

.AVIATION...An upper trough axis extending southward from
the British Columbia coast will shift inland late today with
westerly flow aloft becoming northwesterly tonight. Low level
onshore flow will increase this afternoon leading to a convergence
zone over central Puget Sound. Areas of MVFR ceilings this morning
will lift to VFR this afternoon except in and around convergence
zone shower activity. Shower activity will diminish tonight with
areas of MVFR ceilings redeveloping by Tuesday morning.

.KSEA...MVFR ceilings expected to lift to VFR by around 18Z. VFR
expected this afternoon, but ceilings may briefly drop to MVFR with
convergence zone shower activity expected in the vicinity of the
terminal 22Z-02Z. Surface winds light southerly becoming
southwesterly 7 to 11 knots midday. Currently expecting a wind shift
to N/NE associated with the convergence zone between 23Z and 03Z
before backing to southerly again this evening.  27

&&

.MARINE...A weak surface trough will continue over the waters early
today before ridging builds over the offshore waters later today
into early Tuesday. The ridge will shift eastward Tuesday night as
another front approaches the coastal waters with increasing
southerlies. A period of gales looks likely over the coastal waters
and near the east entrance to the strait just ahead of the front
Wednesday into Wednesday evening. Strong post-frontal onshore flow
will follow Wednesday night into early Thursday with potential gales
across the inland waters...including Puget Sound and Hood Canal.
Another vigorous front is expected to reach the area Thursday night
into early Friday with headlines anticipated for all waters.

Coastal seas will briefly dip below 10 feet later today into Tuesday
before building back into hazardous double digits Wednesday through
most of the remainder of the week.  27

&&

.HYDROLOGY...At this time, flooding is not expected across most
of the area`s rivers over the next 7 days. The exception remains
the Skokomish River, which could enter flood stage late in the
week as a series of wet systems move across the area.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 5 AM PDT early this morning 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-Grays Harbor Bar.

     Small Craft Advisory from 3 PM this afternoon to midnight PDT
     tonight for Central U.S. Waters Strait Of Juan De Fuca-East
     Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$