textproduct: Seattle/Tacoma

SYNOPSIS

A more active pattern will set up over the Pacific Northwest over the next week, bringing periods of lowland rain, mountain snow, and breezy winds to western Washington.

SHORT TERM /TODAY THROUGH THURSDAY/

A frontal system will continue to push inland across western Washington throughout the day today, marking a patt ern change to more active conditions over the next week. Showers will continue to fill in across the region this morning, accompanied by breezy winds with gusts around 25 to 30 mph in the windiest locations. Snow levels will stay above 5000 feet today, limiting snow accumulations to above the passes.

As the upper level trough digs into the region into Wednesday, onshore flow will increase as post frontal showers continue across the region. Temperatures will cool several degrees and snow levels will lower closer to 3000 to 4000 feet. This will allow for a few inches of snow accumulation through the Cascade passes on Wednesday, with Snoqualmie and Stevens Passes on track to see roughly 2 to 4 inches of snow accumulations. Models also continue to highlight the potential for a Puget Sound Convergence Zone to develop on Wednesday, which may produce locally heavy rain and a few lightning strikes.

Thursday will continue a cooling trend under northwest flow aloft, with continued shower activity mainly over the mountains. Most lowland locations will struggle to reach 50 degrees, especially with onshore flow and cloudy skies persisting.

LONG TERM /THURSDAY NIGHT THROUGH MONDAY/

Continued wet and breezy conditions are expected through the weekend and into early next week as a series of systems parade across the Pacific Northwest. Periods of mountain snow and lowland rain will continue, alongside breezy winds and slightly cooler temperatures.

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AVIATION

Westerly flow aloft becoming southwesterly early Tuesday. Weak onshore flow in the lower levels.

VFR ceilings for most terminals until around 12Z. Afterward, expect stratus deck with 1000-2000 foot ceilings to move inland. Stratus will continue to move inland with MVFR ceilings over the entire area by 12-15Z. Local IFR ceilings along the coast. Little change throughout the day with MVFR cigs prevailing with light precipitation at times.

KSEA...VFR conditions this evening with ceilings lowering to MVFR by 12Z-15Z. MVFR ceilings continuing for the rest of the day. Southeast wind 4 to 8 knots becoming southerly 6 to 10 knots after 12z. Rain likely in the afternoon generally after 00Z.

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MARINE

High pressure continues to break down across the waters, with relatively light winds and small seas given the weak gradients. This break will be short-lived, though, as the next frontal system begins to approach the waters this afternoon. While the front isn't particularly strong, expect southerly winds to 20 kt with frequent gusts to 25 kt spreading over the coastal waters early this morning. Over the coastal waters, expect the seas to be quite choppy as short period waves build; the winds aren't strong enough or long duration enough to build much higher than 6 ft, but with dominant periods 6 to 7 seconds it will be rough.

Winds will be coming up again through the Strait of Juan de Fuca on Wednesday night, with coastal seas building to 11 feet on Thursday as the next front progresses through the area.

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HYDROLOGY

No river flooding is expected during the next seven days.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 1 AM PST Wednesday 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.