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fxus66 ksew 170458 
afdsew

Area forecast discussion
National Weather Service Seattle Washington
858 PM PST Sat Dec 16 2017

Synopsis...a weakening warm front will pass mainly to our north
overnight. Expect a cold front to approach from the northwest
during the day Sunday, and then stall over the region Sunday
night. This will keep conditions wet and unsettled on Monday. A
stronger cold front will bring gusty winds to the area on
Tuesday, along with heavy snow in the mountains.

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Short term...
precipitation was occurring over much of the County Warning Area at this time.
Expect wet weather overnight through Sunday ahead of a frontal
system. The weakening warm front is expected to mainly pass to
our north overnight. The cold front will approach the area from
the northwest during the day Sunday.

The cold front will stall over the region Sunday night into
Monday with strong, moist, westerly flow over the area. The main
impact is possible heavy snow in the mountains, especially the
north and central Cascades between Mount Baker and Stevens Pass. A
Winter Weather Advisory is in effect from Sunday afternoon
through Monday morning. Snow levels are tricky and may waver
between 4,000 and 5,000 feet with generally 3 to 11" expected.
Snow levels will then lower to around 3,500 feet early Monday.
Snoqualmie Pass should see mainly rain or a rain/snow mix.

In The Lowlands, cloudy and rain at times Sunday through Monday.
Total rainfall amounts will range from 1" along the coast to
0.50-1.00" in the interior. Temperatures will mainly stick in the
40s for both highs and lows, with a few low 50s possible both
Sunday and Monday afternoon.

A stronger and wetter Pacific frontal system will impact the area
on Tuesday. Heavy snow is possible in the mountains and snow
levels will be lower - dropping to around 2,000 to 3,000 feet
Tuesday night. It'll be windy too, especially with the frontal
passage Tuesday afternoon. However, the models keep waffling on
the low strength and tracking. For now it just looks like a
blustery front and winds are below Wind Advisory criteria.
Showers will taper off Tuesday night as this system exits. 33

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Long term...
another pattern change will take place on Wednesday as a strong
upper level ridge builds over the NE Pacific. This gives western
Washington dry, northerly flow which will help scour out the low
clouds and moisture. At this time, the ridge is dominant through
the extended forecast with dry weather through at least Christmas
day. With a drier air mass in place, expect low temps in the 20s
to lower 30s with highs in the lower 40s. 33

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Aviation...a warm front will move over the area tonight and
remain over the area Sunday with westerly flow aloft. The air mass
is moist and stable.

Ksea...mostly mid level ceilings this evening will lower to MVFR
low clouds as a warm front moves onshore. MVFR low clouds are
expected to persist into Sunday. South wind 4-8 knots will
increase to 10-15 knots and become gusty Sunday. Schneider

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Marine...a warm front will bring Small Craft Advisory strength
winds to most waters tonight and Sunday. There will be relative
lull in between weather systems Monday. A stronger frontal system
will move through the area Monday night and Tuesday. Gales are
likely for the coastal waters with this system. Offshore flow will
develop Wednesday and continue into Thursday. Schneider

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Hydrology...river flooding is not expected the next 7 days.

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Sew watches/warnings/advisories...
Washington...Winter Weather Advisory from 10 am Sunday to 10 am PST Monday
for Cascades of Snohomish and King counties-Cascades of
Whatcom and Skagit counties above 3500 feet.

Pz...Small Craft Advisory until 10 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.

Small Craft Advisory until 4 PM PST Sunday for Admiralty Inlet-
East Entrance U.S. Waters Strait of Juan de Fuca-northern
inland waters including the San Juan Islands.

Small Craft Advisory from midnight tonight to 4 am PST Monday
for Puget Sound and Hood Canal.

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