textproduct: Seattle/Tacoma

SYNOPSIS

Rainfall coverage and intensity is tapering down but significant river flooding impacts will continue. High pressure brings mainly dry weather into Saturday. Wet and unsettled conditions are favored to continue into much of next week.

SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/

Bands of showers still present on latest radar imagery, one over the northern third of the CWA mainly impacting Whatcom, Skagit and northern Snohomish counties and another over Jefferson, Grays Harbor, Mason, northern Thurston and Pierce counties. Activity within each band is generally light, although isolated patches of moderate rainfall are possible /but short lived/. Inherited forecast remains on track, showing that as the upper level ridge over the eastern Pacific continues to build that it will limit the amount of moisture coming into the area over the short term, but does not remove it completely. As such, the risk for showers here and there will continue into the weekend. Fortunately, this light activity should not impact local flooding and the pattern overall will allow waters to gradually recede.

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LONG TERM /SUNDAY THROUGH THURSDAY/

From Previous Discussion...Another wet pattern is forecast starting Sunday and stretching into Monday as moist S/SW flow sets up again over western WA. Snow levels are high at 7,000-8,000 feet meaning more rain in the mountains with the possibility of renewed or prolonged flooding depending on the river. Broad troughing keeps the weather active moving toward midweek with the focus then turning toward heavy mountain snow. Snow levels are forecast to lower to around 2,500-4,000 feet with accumulating snow at all mountain passes. More rain and mountain snow is forecast late in the week. 33

AVIATION

Flow is becoming light northwest aloft as an atmospheric river system moves out of the region. Ceilings are a mix of MVFR and VFR with overcast decks (with a couple spots still reporting IFR). Winds this afternoon vary between SE to NE at 4-6 kt, and will become calm to light southerly (less than 5 kt) overnight. A few showers will linger in the northern and Cascade terminals, otherwise a chance of showers will remain on the coastal terminals Friday. Ceilings will lower down to IFR (with pockets of LIFR) Friday morning with improvements to MVFR in the afternoon. Some mist is possible with visibilities down to 3-6 mi (a few south interior and coastal terminals may see visibilities less than 2 mi). Winds Friday are out of the SW 4-8 kt.

KSEA...Mix of MVFR/low VFR ceilings through the afternoon and evening. Ceilings are expected to drop to IFR after 14Z with a lower chance of LIFR conditions. Improvement to MVFR is expect after 21Z Friday afternoon. Few vicinity showers will taper back through tonight. Winds NE 4-8 kt will decrease and become light and variable from roughly 05Z through 08Z as they become calm. Will increase again out of the SW 4-8 kt late Friday morning through the afternoon.

HPR

MARINE

A cold front will move out of the waters today, with higher pressure building in behind the system. A few showers will linger post-front in the interior waters through tonight, and a slight chance for showers remains in the coast Friday and Saturday. Small craft advisories continue for seas in the coastal waters through tonight (8-11 ft). They will drop to 4-6 ft Friday and increase to 6-8 ft Sunday. The next system with approach the waters Sunday into Monday, with another system to follow towards the middle of the week. There is a medium chance of seeing wind gusts to gale force Monday in the coastal waters and Strait of Juan de Fuca (with a high chance of small craft gusts in remaining interior waters). The gusty winds will likely continue through Wednesday. Seas will also increase up to 14 to 17 ft Monday, then dropping to 11 to 14 ft Tuesday through midweek.

HPR

HYDROLOGY

While some area rivers have crested, particularly rivers in the Olympic Peninsula basins, other rivers continue to rise to significant or record-breaking levels, especially over the western Cascades. Some rivers that are slower to respond, including the Nooksack, Skagit, and Snohomish, will take a few more days to fully crest and lower below flood stage.

* Numerous River Flood Warnings remain in effect across western Washington, with varying times and flood levels.

* A Flash Flood Watch remains in effect for a potential levee failure of the Skagit River below Sedro-Wooley to the mouth of the Skagit River through late Friday.

* A Flood Watch remains in effect through Friday across all of western Washington.

With very wet antecedent soil conditions, the landslide threat across the region has increased with this system, and several landslides and mudslides have already occurred in steep terrain across western Washington. Potential has also increased for debris flows over area burn scars, which continue to be monitored.

While the threat of urban flooding has decreased, the threat of small stream flooding, as well as for areas with poor drainage, continues to pose a risk of localized nuisance flooding and ponding on roadways. Low water crossings may become impacted or impassable.

The latest river observations and forecasts can be found at water.noaa.gov.

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SEW WATCHES/WARNINGS/ADVISORIES

WA...Flood Watch through Friday afternoon for Cascades of Pierce and Lewis Counties-Cascades of Snohomish and Northern King Counties-Cascades of Southern King County-Cascades of Whatcom and Skagit Counties-City of Seattle-Downtown Everett / Marysville Area-Eastern Kitsap County-Eastern Strait of Juan de Fuca-Eastside-Foothills and Valleys of Central King County-Foothills and Valleys of Pierce and Southern King Counties-Foothills and Valleys of Snohomish and Northern King Counties-Foothills and Valleys of Thurston and Lewis Counties-Foothills and Valleys of the North Cascades-Foothills of the Western and Southern Olympic Peninsula-Grays Harbor County Coast-Island County- Lake Crescent Area Including US 101-Lower Chehalis River Valley-Lowlands of Lewis and Southern Thurston Counties- Lowlands of Pierce and Southern King Counties-Lowlands of Western Skagit and Northwestern Snohomish Counties- Lowlands of Western Whatcom County-Middle Chehalis River Valley-Northern Hood Canal-Northern Washington Coast- Olympia and Southern Puget Sound-Olympics-Port Townsend Area-San Juan County-Shoreline / Lynnwood / South Everett Area-Southern Hood Canal-Western Strait of Juan de Fuca- Willapa and Black Hills.

Flash Flood Watch through late Friday night for Lowlands of Western Skagit and Northwestern Snohomish Counties.

PZ...Small Craft Advisory until 4 AM PST Friday 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.