textproduct: Seattle/Tacoma

SYNOPSIS

A cold front will pass over the area this afternoon, bringing breezy winds, lowland rain, and mountain snow. Active pattern will continue with lowland rain and heavy mountain snow through the end of the week and into the weekend as a weak atmospheric river develops.

LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/

Ensembles showing an upper level ridge building offshore pushing the weak atmospheric river southward. Northwesterly flow develops on Saturday keeping showers around the area, mostly in the Cascades along with mountain snow continuing. Guidance is continuing to show another atmospheric river attempting to move over the ridge into western Washington Sunday/Monday. Snow levels rising upwards to 7000 to 8000 feet with more rain on the way. Uncertainty remains of the ridge will push the river upwards to BC. Will continue to monitor the forecast as it evolves.

Mazurkiewicz

AVIATION

A trough in the Gulf of Alaska will continue to drive a strong upper level jet over the region. This will drive a strong frontal system through the TAF period, with the warm sector passing through this afternoon/evening, and a stronger cold front shortly behind Thursday morning. Rain will continue to fall in the lowlands, with snow in the mountains. Some of the precipitation may be heavy at times, reducing visibilities down to IFR. The precipitation coverage will lesson Thursday. Ceilings are favored to remain MVFR in the majority of the interior terminals, with IFR/LIFR in the mountains/coastal terminals. Ceilings trend Thursday towards MVFR/VFR, although the chances of ceilings decreasing towards IFR increases Thursday evening. Winds will continue to pick this afternoon into Thursday morning, with winds peaking at 20-25 kt (sustained) with gusts to 30- 35 kt (a few gusts to 40 kt will be possible). There will also continue to be instances of speed shear (due to higher winds aloft, but the direction from aloft to the surface will continue to remain out of the west). Winds will diminish Thursday, but a few gusts to 20 kt will remain likely at times.

KSEA...Steady rain with reduced visibilities at times will continue through tonight - will taper to showers Thursday morning. Ceilings are favored to remain MVFR through the TAF period (although there is a low chance of improvement to VFR from 06Z - 15Z). Southwest winds to increase to 20 kt gusting to 35 kt this evening into Thursday morning, diminishing to 8-12 kt gusting to 20 kt during the day.

HPR

MARINE

A strong weather system today will bring strong winds and high seas to the region. Winds will continue to increase this afternoon to Gale Force across area waters today, with Storm Force winds across the Eastern Strait of Juan de Fuca. Seas will also quickly build along the coast today, peaking at around 18-20 feet over the outer coastal waters before quickly receding on Thursday to below 10 feet.

Additional systems will cross the waters later this week. A weaker system will move over the waters on Thursday and Friday, with winds shifting to the north Friday morning. Another system will follow on Sunday, bringing potential for SCA winds across the coastal waters. Latest guidance suggests seas will remain below 10 ft through the weekend.

15

HYDROLOGY

The heavy mountain precipitation but with lower snow level scenario will continue to make river forecasting difficult into Sunday. QPF values continuing to trend slightly lower for western Washington has kept most hydrographs below flood stage for area rivers except the Skokomish River. However, the Skokomish River continues to run lower than the latest river forecast. A Flood Watch remains in effect for Mason County for the potential for the Skokomish River to briefly reach minor flood stage by early Thursday, with additional chances for flooding early next week. While the remainder of the river forecasts to not highlight any flooding, plenty of rivers from King county southward will crest in action stage over the next few days. Will be keeping an eye on the scenario developing the first part of next week with the higher snow levels much more conducive to flooding possibilities for the rivers.

Felton/15

SEW WATCHES/WARNINGS/ADVISORIES

WA...Wind Advisory from 3 PM this afternoon to 6 AM PDT Thursday for 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-Port Townsend Area-San Juan County- Shoreline / Lynnwood / South Everett Area-Southern Hood Canal-Western Strait of Juan de Fuca-Willapa and Black Hills.

Winter Weather Advisory until 6 PM PDT this evening 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.

Blizzard Warning from 6 PM this evening to 5 AM PDT Thursday 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- Olympics.

Winter Storm Warning from 5 AM Thursday to 5 AM PDT Saturday 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- Olympics.

Flood Watch from 5 PM PDT this afternoon through Thursday afternoon for Foothills of the Western and Southern Olympic Peninsula-Middle Chehalis River Valley-Olympia and Southern Puget Sound-Olympics-Southern Hood Canal- Willapa and Black Hills.

PZ...Small Craft Advisory until 2 AM PDT Thursday for Grays Harbor Bar.

Gale Warning until 2 AM PDT Thursday for Admiralty Inlet- Central 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.

Storm Warning until 2 AM PDT Thursday for East Entrance U.S. Waters Strait Of Juan De Fuca.

Gale Warning until 2 AM PDT Thursday 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.