Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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324 FXUS66 KSEW 191719 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 919 AM PST Sun Nov 19 2017 .SYNOPSIS...
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A vigorous front will move slowly through Western Washington this afternoon and evening. Weak high pressure will be over the area Monday. A strong warm front will arrive Tuesday. The middle of the week will be mild, rainy, and perhaps windy at times.
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&& .SHORT TERM...
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A front will shift southeast through Western Washington this afternoon and evening then stalling over southwest Washington and Western Oregon tonight. Wind advisories are in effect for the typically windy areas. The precip will pick up this afternoon and shift south through the area into the evening--the rain will probably start around 2pm in Seattle if the latest HRRR is right. Monday looks like a pretty quiet day between weather systems. On Tuesday the strong warm front we have been talking about arrives, with sky high snow levels through the middle of the week. .LONG TERM...After a pretty decent round of rain Tuesday and Tuesday night--with some heavy rain in the mountains, the heavy precip will be north of the area on Wednesday. There will still be rain at times over Western Washington--but this lull on Wed will help a great deal with the rivers. Then on Thursday the rainfall picks up again--but precip amounts in the models are actually pretty modest.
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&& .AVIATION...
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A strong, windy, and wet cold front will gradually slide southeast through Western Washington this afternoon and evening. Strong southerly winds are expected before frontal passage (fropa), then much lighter northwest wind expected following fropa. Strong westerly flow above 100 through tonight. A brief period of high pressure on Monday will lead to more benign conditions on Monday afternoon. KSEA...Deteriorating conditions today until a cold frontal passage (fropa) around 05z. Rain will develop around 22z and get heavy enough around 01z to 04z to reduce vsby. Cigs will fall rapidly once rain begins. Strong low-level winds will precede the front. S-SW winds at 2,000-foot will reach 50 knots in the hours preceding fropa, and 4,000-foot winds will reach 65-75 knots. Rain and low-level wind will ease quickly in the hours following fropa. Haner
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&& .MARINE...
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A strong cold front extending WSW from central Vancouver Island into the Pacific will slowly drag southeast down the British Columbia coastline and then push southeastward through the coastal and inland waters late this afternoon and this evening. In advance of the front, southerly gales are either occurring already or expected this afternoon. Once the front passes, winds will rapidly ease and shift to the northwest behind the front. Frontal passage timing and easing of wind will range from about 3 PM near Cape Flattery to almost midnight at the south end of Puget Sound. High pressure will bring light winds to the waters on Monday. A strong warm front will push northward through the waters on Tuesday. A strong low pressure center developing well offshore will push northeast into Haida Gwaii on Wednesday. Haner
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&& .HYDROLOGY...
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The Skokomish river in Mason county will probably get up near flood stage tonight and Monday and there is a flood watch in effect. The precip next week will be heaviest Tuesday and Tuesday night, then there is a lull on Wednesday, and then it picks up a bit Thursday but is not heavy. We will have to watch the rivers with the very high snow level around mid-week, but the Skokomish River in Mason county is the only one that is an obvious threat--if not tonight and Monday, then certainly on Tuesday.
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&& .SEW WATCHES/WARNINGS/ADVISORIES...
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WA...Winter Weather Advisory until 10 PM PST this evening for Cascades of Whatcom and Skagit Counties. Flood Watch through Monday morning for Hood Canal Area-Lower Chehalis Valley Area-Olympics. Wind Advisory until 6 PM PST this evening for Admiralty Inlet Area-Central Coast-North Coast-San Juan County-Western Skagit County-Western Whatcom County. PZ...Small Craft Advisory for rough bar until noon PST Monday for Grays Harbor Bar. Gale Warning until 9 PM PST this evening for 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. Gale Warning until 6 PM PST this evening for Admiralty Inlet- Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm-East Entrance U.S. Waters Strait Of Juan De Fuca- Northern Inland Waters Including The San Juan Islands-Puget Sound and Hood Canal-West Entrance U.S. Waters Strait Of Juan De Fuca. Small Craft Advisory until 3 AM PST Monday for Central U.S. Waters Strait Of Juan De Fuca.
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&& $$ www.weather.gov/seattle You can see an illustrated version of this discussion at www.wrh.noaa.gov/sew/gafd/latest_webafd.html

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