Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 201736
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
930 AM PST Sat Jan 20 2018

.SYNOPSIS...A strong front will move through the area tonight and
Sunday morning.  Another strong front should cross Western Washington
Tuesday night and Wednesday. A cool showery upper trough will reach
the area Thursday.

&&

.SHORT TERM...A strong front will move into the area tonight. Strong
southeasterly gradients will develop and a high wind warning is in
effect for the typical windy spots. There will be more snow in the
mountains and a winter storm watch is in effect. The Skokomish river
in Mason county should get up above flood stage as heavy rain falls
in the lower elevations of the Olympics, especially as strong south
winds aloft push moisture into the terrain in that river basin.
Precip will taper off Sunday into Monday, though no model is
completely dry. The air mass will be unstable on Sunday afternoon,
with showers everywhere and thunder possible on the coast. Monday
will not be as unstable, but moist onshore flow will still bring
showers.

.LONG TERM...Early Tuesday looks dry. Then a weak front will
move quickly through the area Tuesday night. Another front will
arrive around Wednesday, and another one Thursday. An upper trough
will cool the air mass considerably Thursday night and Friday, with
showers and low snow levels resulting. Burke

&&

.HYDROLOGY...The Skokomish river in Mason county has a good
chance to get above flood stage on Sunday, otherwise River flooding
is not expected for the next 7 days. I have tried to put a new
forecast in for the Skokomish river that shows the river rising to
flood stage of 16.5 feet late Sunday morning, then cresting at 16.8
feet Sunday afternoon, then falling below flood stage around
daybreak Monday. For whatever reason the forecast isn`t showing up
on the website as of 930am, but I`ll keep trying to get it out.

Forecast rainfall tonight and early Sunday will push the USGS
landslide indices close to thresholds for shallow landslides.

&&

.AVIATION...A strong cold front will reach the coast and move
inland, all on Sunday morning. S-SE surface wind will become
strong in advance of the front tonight. Strong 850-700 mb winds
will peak near 70 knots from the southwest on Sunday morning. The
air mass will be moist and a little unstable today, becoming more
stable tonight. A few hours of heavier rain are expected Sunday
morning, just in advance of the front. Easterly wind component
will generally hold cigs above 025, except lower near Hood Canal.

KSEA...Will be quite showery at the terminal until about 20z
(noon), then fewer showers this afternoon and evening. Cigs will
slowly lift through this evening and low-level wind takes on a
drying easterly component. Strong winds aloft expected Sunday
morning. Winds at 045 will peak SW 65 knots, and 2000-foot winds
will peak southerly around 50 knots. Haner

KSEA...Mainly MVFR conditions with ceilings at FL015-025 today.
Low level southeasterly flow will help ceilings rise to FL035
tonight. Wind 19011kt early easing to 16007kt this evening then
rising to SE 15 kt after 06Z as winds at FL025 rise to S 55 kt.
Albrecht

&&

.MARINE...East-southeast gradient will tighten significantly
tonight in advance of a strong cold front that will cross the
waters on Sunday morning. Storm-force winds to near 50 kt appear
likely over the coastal waters and at the east entrance, but
cannot be ruled out over the Northern Inland Waters. The remaining
inland waters will likely see gale force winds. In Puget Sound,
gales should mainly be confined to the north end of the Sound.

Forecast models show an active pattern continuing for much of the
incoming week with strong fronts or low pressure systems moving
through the waters Tuesday through Thursday. These systems may
produce additional rounds of gale force winds. Haner

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory until 10 AM PST this morning for
     Cascades of Pierce and Lewis Counties-Cascades of Snohomish
     and King Counties-Cascades of Whatcom and Skagit Counties.

     Winter Storm Watch from this evening through Sunday evening for
     Cascades of Pierce and Lewis Counties-Cascades of Snohomish
     and King Counties-Cascades of Whatcom and Skagit Counties-
     Olympics.

     Wind Advisory from 10 PM this evening to noon PST Sunday for
     Everett and Vicinity-Hood Canal Area.

     High Wind Warning from 8 PM this evening to noon PST Sunday for
     Admiralty Inlet Area-San Juan County-Western Skagit County-
     Western Whatcom County.

     High Wind Warning from 6 PM this evening to 10 AM PST Sunday for
     Central Coast-North Coast.

     Wind Advisory from 10 PM this evening to 10 AM PST Sunday for
     Eastern Strait of Juan de Fuca.

PZ...Small Craft Advisory for rough bar until 3 PM PST Sunday for
     Grays Harbor Bar.

     Small Craft Advisory until 6 PM PST this evening 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-West Entrance U.S. Waters
     Strait Of Juan De Fuca.

     Storm Warning from 6 PM this evening to 9 AM PST 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.

     Storm Warning from 6 PM this evening to 10 AM PST Sunday for
     East Entrance U.S. Waters Strait Of Juan De Fuca.

     Gale Warning from 6 PM this evening to 10 AM PST Sunday for
     Admiralty Inlet-Central U.S. Waters Strait Of Juan De Fuca-
     Northern Inland Waters Including The San Juan Islands.

     Gale Warning from 6 PM this evening to 9 AM PST Sunday for West
     Entrance U.S. Waters Strait Of Juan De Fuca.

     Gale Warning from 10 PM this evening to 10 AM PST Sunday for
     Puget Sound and Hood Canal.

&&

$$

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