Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 162155
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
255 PM PDT Sat Sep 16 2017

.SYNOPSIS...A front will bring rain later Sunday. An upper trough
and additional weather systems will keep the weather cool and
showery into the middle of next week. Drier weather is likely late
next week.

&&

.SHORT TERM...A weak upper ridge will shift inland tonight with
high clouds. Smoke from fires over the Cascades will continue to
affect the Puget Sound lowlands tonight. Models suggest the smoke
will push east of the area Sunday as westerly flow kicks in.

A frontal system will bring some rain later Sunday. Rain should
reach the coast in the morning and spread into the interior in the
afternoon. Highs will cool into the 60s Sunday.

Monday and Tuesday will be cool and showery with an upper trough
over the area. Snow levels will be 5000-5500 feet. Highs will be
about 10 degrees below normal and struggle to reach 60 degrees in
some spots. Schneider

.LONG TERM...A vigorous upper short wave will drop down from the
northwest Tuesday night and swing inland Wednesday. This will
bring a period of rain Tuesday night followed by showers
Wednesday. An associated surface low is expected to track across
the south part of the area. Models disagree with the track and
strength of the low. For now, it looks like it will be far enough
to the south that most of the area will not get much wind but this
could change. Stay tuned.

Drier northerly flow aloft will develop over Western Washington
Thursday. It looks like most of the area will be completely dry by
Friday and Saturday. Schneider

&&

.AVIATION...A weak disturbance has brought mid and high clouds to
the area. It is also smoky today from the Cascade fires. Areas of
low clouds should increase over the coastal waters through tonight
and some areas of morning low clouds might push into the interior of
Western Washington Sunday morning. A cold front will bring
rain to the area Sunday afternoon with lowering cigs.

KSEA...Mid and high clouds today from a weak disturbance, smoky
skies, and some low marine stratus could push in late tonight. Any
morning low clouds that make it into Seattle Sunday morning will be
mixed into the increasing clouds with the cold front Sunday
afternoon.

&&

.MARINE...Onshore flow and westerlies will develop in the Strait
of Juan de Fuca tonight. Southerly winds will come up pretty quick
over the coastal waters Sunday morning-- with 20-30kt south winds
developing by mid to late morning. The winds over the coastal
waters will shift to northwest with the frontal passage in the
afternoon. Over the inland waters southerly winds up to around
20kts will be followed by a typical Puget Sound Convergence Zone
wind pattern with onshore flow through Sunday night behind the
front. There will be additional weather systems moving through the
area Monday through Wednesday for more onshore flow.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 6 AM to 10 PM PDT Sunday 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 6 PM this evening to 3 AM PDT Sunday
     for Central U.S. Waters Strait Of Juan De Fuca-East
     Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$

www.weather.gov/seattle

You can see an illustrated version of this discussion at
www.wrh.noaa.gov/sew/gafd/latest_webafd.html



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