Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 242255
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
255 PM PST Sat Feb 24 2018

.SYNOPSIS...Cool and unsettled weather will continue through the
end of next week. A frontal system will move bring rain and
mountain snow tonight and Sunday. There will be a brief break in
the action Monday before the next system arrives Monday night and
Tuesday. A wetter system will arrive Wednesday night or Thursday.

&&

.SHORT TERM...A frontal system will move into the area later
tonight and push inland Sunday bringing some breezy to windy
conditions. Snow levels will be low but onshore flow should keep
it warm enough for just cold rain in the lowlands. The Cascades
will get a lot of snow tonight and Sunday - probably one to two
feet. A winter storm warning is in effect. There will probably be
another PSCZ behind the frontal system later Sunday. Otherwise, it
will be showery and a bit unstable behind the front Sunday.

An upper trough will settle over the area Sunday night and then
push a bit inland on Monday. A threat of lowland snow will return
again Sunday night/early Monday morning as snow levels lower to
near sea level. However, most of the area will be dry by then with
just isolated showers. New snow accumulations over the lowlands,
if any, should be light and isolated.

Yet another system will drop down from the northwest later Monday
night/Tuesday morning. Once again, snow levels will be low enough
for a threat of some snow over the lowlands, at least in the
morning. Overall, the system is pretty weak and QPF is light which
should limit accumulations and any associated impacts. Schneider

.LONG TERM...A wet frontal system will reach the area Wednesday
and push inland Wednesday night. A chilly upper trough will
settle over the Pacific Northwest after that for a chance of
showers with low snow levels again. Models are in rather poor
agreement by the weekend and the forecast is a broad brush for
now. Schneider

&&

.AVIATION...Moderate westerly flow aloft tonight will ease somewhat
Sunday afternoon. At the surface, onshore flow will increase tonight
after a front moves through the region. The air mass is moist and
stable. Rain will spread into the area from the northwest tonight
and change to showers by Sunday afternoon.

Ceilings are generally VFR 4-6k ft. High clouds are increasing.
Rain will develop after 06Z, with snow in the mountains. Ceilings
will become MVFR 09Z-12Z and remain MVFR most of the day.

KSEA...Discussion above applies. South wind 8-12 kt this evening
will increase to 15g25 kt after 06Z, then become southwesterly after
the front passes Sunday morning. CHB

&&

.MARINE...Onshore flow will increase tonight after a front moves
through the area. Gale warnings are in effect for strong onshore
flow on the coast and in the strait, with small craft advisories
for the remaining waters. Winds will ease Sunday afternoon and
evening.

Weak high pressure over the area Monday will be followed by another
front on Tuesday. The front Tuesday looks to have mostly small craft
advisory level winds. Another front will arrive around Wednesday
night or Thursday, and this one could have gale force winds. CHB

&&

.HYDROLOGY...River flooding is not expected for the next 7 days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Storm Warning from 7 PM this evening to 7 PM PST Sunday
     for Cascades of Pierce and Lewis Counties-Cascades of
     Snohomish and King Counties-Cascades of Whatcom and Skagit
     Counties.

PZ...Gale Warning until 4 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-West Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory for rough bar until 4 AM PST Monday for
     Grays Harbor Bar.

     Small Craft Advisory until midnight PST tonight for Central U.S.
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
     Strait Of Juan De Fuca.

     Gale Warning from midnight tonight to 4 PM PST Sunday for
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance
     U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 7 PM PST Sunday for Admiralty Inlet-
     Northern Inland Waters Including The San Juan Islands.

     Small Craft Advisory from 10 PM this evening to 4 PM PST Sunday
     for Puget Sound and Hood Canal.

&&

$$

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