Forecast Discussion for SEW NWS Office
FXUS66 KSEW 171634

Area Forecast Discussion
National Weather Service Seattle WA
935 AM PDT Sun Oct 17 2021

.SYNOPSIS...A weak front will move over Western Washington today and
then dissipate tonight. Monday and Tuesday will see a break between
weather systems. The weather pattern turns wet again for the second
half of the week.


.SHORT TERM /TODAY THROUGH TUESDAY/...The frontal system that was
stalled near the north coast Friday and Saturday is splitting and
the stronger portion of the system is moving toward nrn Calif. The
weaker northern remnants of the system are moving over Western
Washington and there are areas of light rain on radar this morning.
At 9am it was raining at Hoquiam, Shelton and Olympia for starters
and it will probably be a drippy day around Seattle before midday as
well. Precip amounts today should be on the light side--probably
around a tenth of an inch, but perhaps a quarter of an inch over
southwest WA. Areas in the north might only see a few hundredths.
There will probably be enough moisture around through Monday morning
for some areas of drizzle or scattered shower activity, mainly in
the convergence zone and into the Cascades, but otherwise there will
be a break between systems with skies clearing somewhat into Monday
night and Tuesday. After patches of morning fog, Tuesday could be a
pretty decent day with light offshore flow. 19

system will reach the area early Wednesday for more rain and
breezy winds (mainly along the coast). The pattern remains active
as we move into Thursday as a deep low spins over the offshore
waters then tracks north toward Haida Gwaii. This system brings
an additional round of rain and breezy winds (coast again) through
Friday. More active weather is anticipated over the weekend as
with a longwave trough over the West. Snow levels drop to around
4500-5000 feet on Saturday with a few inches of snow on the higher
mountain peaks. 33


.AVIATION...Southwesterly flow aloft becoming southerly as upper
level trough digs south off the coast. Weakening front moving into
the Western Washington interior and dissipating tonight. Ceilings
below 1000 feet along the coast with visibility 1-3sm in rain
until and near the Strait of Juan de Fuca. For the interior
ceilings near 5000 feet lowering to 1000-2000 feet with visibility
3-5sm in light rain after 00z. Convergence zone developing over
Snohomish county with ceilings below 500 feet and visibility
1-3sm in light rain 03z-09z. Little improvement Monday morning.

KSEA...Ceilings near 5000 feet lowering to 1000-2000 feet after
03z. Southerly wind 4 to 8 knots becoming variable around 00z.


.MARINE...A frontal system will move over the inland waters and
dissipate tonight. Winds will remain light overall, except for
the Outer Coastal Waters where post-frontal northwesterlies will
hover right around SCA level. As the front moves inland a westerly
push down the central and east Strait is anticipated with winds
reaching lower-end SCA level. The weather will become more
benign/quiet for Mon/Tues as weak high pressure influences the
area. There could be some marine fog today into tonight. Fog is
also likely Tuesday morning.

An active upper level pattern suggests that additional storm systems
will affect the waters from mid-week onward. The first will move
through Wednesday. Southerly winds will pick up ahead of the system
early Wednesday, likely yielding the next round of headlines for
small craft level winds, with breezy conditions likely continuing
through the evening with rain eventually accompanying. Timing and
details of following storm systems will be ironed out in the coming
days, but it is a safe bet at this point that additional wind
headlines will be needed.

NW swells today around 7 feet. They will increase noticeably with
the storm systems this week, likely increasing to 10-12 ft
Wednesday out of the SW and 11-13 ft towards the end of the week
out of the W/SW. Kovacik/Felton


PZ...Small Craft Advisory from 6 PM this evening to 5 AM PDT Monday
     for Central U.S. Waters Strait Of Juan De Fuca-East
     Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 6 PM PDT this evening for Coastal
     Waters From Cape Flattery To James Island 10 To 60 Nm-
     Coastal Waters From James Island To Point Grenville 10 To
     60 Nm-Coastal Waters From Point Grenville To Cape
     Shoalwater 10 To 60 Nm.



NWS SEW Office Area Forecast Discussion