Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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055 FXUS66 KSEW 242255 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 255 PM PST Sat Feb 24 2018 .SYNOPSIS...
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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.
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&& .SHORT TERM...
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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
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&& .AVIATION...
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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
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&& .MARINE...
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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
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&& .HYDROLOGY...River flooding is not expected for the next 7 days. && .SEW WATCHES/WARNINGS/ADVISORIES...
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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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