River Flood Warning 85, NWS Seattle, WA

Area Forecast Discussion...CORRECTED
National Weather Service Seattle WA
823 PM PST Sat Dec 29 2018

.SYNOPSIS...A front will move inland tonight with showers
tapering through Sunday and ending by Sunday night. High pressure
aloft will bring dry weather Monday and Tuesday. Rain will return
Wednesday and Thursday as a frontal system stalls over the area.
A trailing cold front will push inland on Friday with rain
changing to showers.

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.SHORT TERM /TONIGHT THROUGH TUESDAY/...A cold front is currently
moving east of the area with steady rain ending. Showers look
pretty isolated behind the front tonight. The exception will be in
a Puget Sound Convergence Zone. The PSCZ will be over central
Puget Sound - perhaps a little further south than normal due to
the west/northwest flow aloft. It looks like the PSCZ will fade
away Sunday morning as onshore flow eases. Snow levels will lower
to 2500-3000 feet tonight and the mountains could pick up several
inches of snow. Advisory amounts are possible depending on where
the convergence zone sets up.

Showers will be mostly confined to the mountains on Sunday. Drier
northerly flow aloft will develop and low level onshore flow will
ease and turn more northerly as well. Isolated showers over the
mountains should end Sunday evening. An upper ridge will move
over the area Monday and Tuesday for dry weather with sunshine at
times. Temperatures will be near normal. Schneider

.LONG TERM /TUESDAY THROUGH SATURDAY/...Models in pretty good
agreement showing a frontal system spreading rain into the area on
Wednesday, stalling the system over the area Wednesday night,
then lifting it a bit north as a warm front on Thursday. While
there are some differences in the details by Thursday, it looks
like a wet period. A trailing cold front will finally push inland
on Friday with rain changing to showers. Models are kind of all
over the place by Saturday but it doesn't look like any organized
systems will be impacting the area. Schneider

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.AVIATION...A front will move inland this evening with westerly
flow aloft becoming northwesterly tonight and northerly on
Sunday. At the surface, onshore flow will ease later tonight and
Sunday. The air mass is moist and slightly unstable. A Puget Sound
Convergence Zone over central Puget Sound will dissipate Sunday
morning.

KSEA...Mostly MVFR low clouds expected tonight and Sunday morning
although the lower ceilings could scatter at times. A Puget Sound
Convergence Zone is expected to remain just north of the terminal
tonight with southwest winds 5-10 knots. VFR low clouds should
scatter late Sunday with winds becoming northerly. Schneider

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.MARINE...Onshore flow tonight will ease on Sunday. Gale force
west winds are expected in the Strait this evening with winds
easing to small craft advisory strength after that. There is a
chance gales could linger in the Strait into the early morning
hours Sunday however. Elsewhere, small craft advisory strength
westerly winds most waters tonight will ease Sunday and Sunday
night. West swell 10-13 feet over the Coastal Waters will
gradually subside Sunday and Sunday night. There is also a
somewhat unusual secondary west swell around 6 feet over the
Coastal Waters that will linger into Sunday and then fade away.

Onshore flow will become light offshore Sunday night and Monday as
high pressure moves into southern British Columbia. Weak high
pressure will be over the area on Tuesday for relatively light
winds. A frontal system will move into the area on Wednesday and
then stall across the area into Thursday. Schneider

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.HYDROLOGY...Minor flooding is occurring on the Skokomish river in
Mason county. A front which brought heavy rain earlier today has
pushed inland and rainfall has tapered. The Skokomish river should
crest later tonight and fall below flood stage on Sunday. No
other rivers are likely to flood tonight through Wednesday.

The next threat for river flooding is Wednesday night and Thursday.
The GFS continues to show a warm front lingering across the area.
This would bring a potential for river flooding especially for
rivers flowing off the Olympics and to a lesser extent the North
Cascades. The ECMWF is weaker and more progressive with less rain
for a much reduced risk of river flooding.

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

PZ...Small Craft Advisory until 3 PM 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-Northern Inland Waters Including The
     San Juan Islands.

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

     Small Craft Advisory from midnight tonight to 2 PM PST Sunday
     for Central U.S. Waters Strait Of Juan De Fuca-East
     Entrance U.S. Waters Strait Of Juan De Fuca.

     Gale Warning until midnight PST tonight 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 AM PST Sunday for West Entrance
     U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until noon PST Sunday for Admiralty Inlet.

     Gale Warning until 11 PM PST this evening for Admiralty Inlet.

     Small Craft Advisory until 9 PM PST this evening for Puget Sound
     and Hood Canal.

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www.weather.gov/seattle