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813
FXUS66 KSEW 141030
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
330 AM PDT Sat Sep 14 2024

.SYNOPSIS...
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Upper level trough over the area today will move south
Sunday night. Western Washington in between features Monday. Front
moving down British Columbia coast spreading rain over the area
Tuesday. Front moving through Tuesday night. Temporary ridge
Thursday with a weak system moving by to the north Friday.
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.SHORT TERM /TODAY THROUGH MONDAY/...
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Satellite imagery shows
frontal system over Eastern Washington with post frontal upper
level trough settling in over Western Washington early this
morning. Widespread showers on the doppler radar with the highest
concentration over the Northwest Interior. Temperatures at 3
am/10z were in the mid 50s.

Upper level trough remaining over Western Washington today keeping
showers in the forecast and highs well below normal. Weak vort max
moving through this afternoon will increase the shower activity.
Increasing onshore flow behind this feature with possible
convergence zone over Snohomish county late in the afternoon.
Highs in the lower to mid 60s.

Trough remaining over the area tonight into Sunday but nothing
organized embedded in the trough. Convergnece zone dissipating in
the evening. With the somewhat unstable air mass scattered
showers will continue through Sunday. Shower activity will not be
as widespread as today. Temperatures remaining cool with some
breaks in the cloud cover allowing temperatures to drop into the
mid 40s to lower 50s Sunday morning. Highs Sunday afternoon again
in the lower to mid 60s.

Upper level trough sinking south Sunday night pulling the shower
activity with it out of the area, Skies clearing overnight. Monday
morning will be the coolest morning since June with some
locations as cool as the lower 40s. Mid 40s to near 50 for the
remainder of the area.

Western Washington in between features Monday with the upper level
trough to the south and an approaching front moving down the
British Columbia coast still well to the northwest. Even with
plenty of sunshine the temperatures aloft will not be very warm
keeping highs below normal, mid 60s to lower 70s.

.LONG TERM /TUESDAY THROUGH FRIDAY/...Models showing good
consistency with a stretching out and weakening front moving
through Western Washington Tuesday night. Rain out ahead of the
front spreading over the area Tuesday. The increasing cloud cover
along with rain developing in the afternoon is a good recipe for
well below normal highs. Not expecting any record breaking low
maximums but it will still be a cool day with highs a couple of
degrees either side of 60. Lows in the 50s.

Post frontal trough digging south Wednesday with shower activity
decreasing during the day. Flat upper level ridge trying to build
into Western Washington Thursday. Weak shortwave riding by mainly
to the north Friday. While the operational runs are pretty much
dry Thursday and Friday the ensembles continue to show a few
solutions with light precipitation. The unimpressive upper level
ridging on the operational runs combined with the ensemble
solutions will keep a slight chance of showers in the forecast
both Thursday and Friday. Highs remaining a little below normal,
in the mid 60s.

Extended models are building a much stronger ridge next weekend
with increasing low level offshore flow for a possible warm start
to fall. Felton
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&&

.AVIATION...
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West-southwest flow aloft today before turning more
southwesterly overnight into early Sunday. Mostly VFR at this hour
(0830z) but MVFR/IFR cigs will become more widespread as the morning
progress. Can`t rule out patches of fog (LIFR) with weak surface
winds and low-level moisture present. VFR conditions should return
by 19-21z. However, convergence zone activity will likely maintain
low cigs over KPAE where MVFR conditions can`t be rule out. A slight
chance (15%) of IFR cigs are possible as well. Low clouds will again
become more widespread overnight into Sunday.

KSEA...VFR conditions in place currently. But, MVFR cigs are to
develop this morning and maintain before VFR returns by 19-20z.
Winds SW 5-10 kt today before veering more ENE overnight into early
Sunday while decreasing in strength. More low stratus possible
into Sunday as well.

McMillian
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&&

.MARINE...
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High pressure over the Pacific waters and low pressure
inland will maintain onshore flow. A post-frontal regime will
increase westerlies down the strait this evening as a SCA has been
issued for the Central/Eastern sections. Winds should ease into the
early morning hours on Sunday. Light northwest winds will continue
Sunday and into the rest of the week. Seas of 3 to 5 feet will build
to 5 to 7 feet Sunday, dropping to 3 to 5 feet Monday before
returning to 5 to 8 feet around midweek.

18/HPR
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&&

.SEW WATCHES/WARNINGS/ADVISORIES...
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WA...None.
PZ...Small Craft Advisory from 4 PM this afternoon to 2 AM PDT Sunday
     for Central U.S. Waters Strait Of Juan De Fuca-East
     Entrance U.S. Waters Strait Of Juan De Fuca.
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&&

$$