textproduct: Seattle/Tacoma

SYNOPSIS

Active weather continues, with a stout front on the way tomorrow evening, lasting into Thursday morning. Additional systems are poised to move through the region through the weekend, with heavy mountain snow and lowland rain expected through this time period. A threat of river flooding remains in the forecast for areas south of Olympia.

SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/

A wave of showers is beginning to make its way into Puget Sound this afternoon. Given the snow levels and present temperatures, this should fall as rain for lowland locations, with some light snow in the Cascades by the time it gets there.

A strong cold front will approach the area tomorrow, driving up the winds by the late morning, peaking late Wednesday into early Thursday morning. Blizzard warnings in the Cascades and Olympics remain intact, but the wind forecast for lowland locations also increased. Winds in the Cascades are still forecast to gust between 35 and 45 mph, but with the 850 mb winds also indicating 50-55 mph winds, high elevation locations could gust higher than that. Additionally, wind advisories have been posted to begin Wednesday afternoon and last through Thursday morning. Winds will begin as strong southwesterly winds, and for areas north of Everett, expect a transition to strong northwesterly winds in the late evening as a strong push occurs through the Strait of Juan de Fuca. Areas south of Everett will remain southwesterly. At the onset of this event, snow levels are forecast to rise to around 5000-6000ft before coming back down late Wednesday night into Thursday morning. During the period where the snow levels are higher, expect a period of rain in the Cascade passes on top of whatever snow has fallen. Temperatures will cool overnight for concerns of re- freezing over the roadways. Travel conditions could be very difficult with all of these factors combined.

QPF amounts in lowland locations will be between 1.5 to 3 inches through Friday for areas from Seattle south, with around a half to one inch in areas north of the metro. The higher amounts are forecast for the Chehalis Valley, where some area rivers are forecast to rise into minor flood stages.

After these hazards begin to taper off early Thursday morning, mountain showers will continue into Friday.

LONG TERM /FRIDAY THROUGH TUESDAY/

Heavy snow is expected to continue on Friday into the weekend, and Winter Storm Watches remain posted for the late week/weekend period. Snow levels remain around 2500 feet or less. By Saturday, area snow levels drop below 1000 feet, so depending on moisture availability, there is also a chance for some of the higher hills amidst the lowland locations to receive a dusting of snow come Saturday morning.

Forecast guidance is still holding onto another potential atmospheric river coming overtop a building ridge to the south of the Pacific Northwest on Sunday into Monday. Right now it's too early to tell how much rain will fall from this system, but confidence is elevated in wet conditions lingering into early next week before the influence of the ridge may become more apparent.

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AVIATION

Mostly VFR this afternoon with pockets of MVFR cigs. A frontal system will continue to progress inland through this evening, bringing widespread shower activity, chances for a few lightning strikes, and breezy winds up to 25-30 kt along the front. Flight conditions will continue to lower tonight with widespread MVFR, with potential for IFR conditions to develop overnight into Thursday morning. More stratiform rain and snow will develop across the region Wednesday morning and lift northward, with another cold front slated to cross the region Wednesday afternoon bringing widespread gusty winds.

KSEA...VFR this afternoon, with increasing chances for MVFR ceilings to develop this evening and overnight as shower activity continues. A lightning strike or two is possible this afternoon, but confidence is not high enough to include in the TAF. Southerly gusts will continue this afternoon to 20-25 kt as a frontal system crosses the region, with winds easing somewhat overnight. More steady rain will move over the terminal Wednesday morning, maintaining MVFR conditions with increasing potential for ceilings below 2000 feet (40% to 50% chance) Wednesday morning. S/SW winds will increase midday Wednesday with gusts briefly reaching 30-35 kt at the terminal Wed afternoon.

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MARINE

Small Craft Advisories remain in effect for the Puget Sound, Admiralty Inlet, and Salish Sea this afternoon and evening as a frontal system progresses inland. SCAs for the coastal waters and Grays Harbor bar remain in effect as well for westerly winds and elevated seas. A much stronger storm system will move over the region on Wednesday, with the potential to bring Gale Force winds to all area waters. Gale Watches for the coastal waters and through the Strait of Juan de Fuca have been upgraded to Gale Warnings, and Gale Watches have been issued for the Puget Sound, Admiralty Inlet, and Salish Sea for potential for gale strength gusts later on Wednesday. A brief window of Storm Force gusts are also possible as hi-res guidance is showing a moderate (30-50%) chance of them occuring over the Central and Eastern Strait on Wednesday evening.

A weaker system will stall over the region Thursday and Friday. The flow will turn northerly on Saturday, then offshore on Sunday as a warm front moves into southern B.C.

Seas remain around 8-13 ft this afternoon before easing to around 7 to 9 feet overnight into Wednesday morning. Seas will briefly rise as high as 15-18 feet across the coastal waters Wednesday afternoon into early Thursday. Seas then ease to around 6 to 9 feet by Thursday afternoon and remain below 10 feet thereafter.

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HYDROLOGY

Moderate to heavy precipitation over the Olympics this week will cause the Skokomish River in Mason County to rise today with flooding possible beginning early Thursday. The river will remain high through the end of the week with additional crests forecast to reach minor flood stage. Flooding is also possible on the Chehalis river from Grand Mound to Grays Harbor, Newaukum River and Skookumchuck River near Bucoda beginning Thursday. South Prairie Creek also has potential to near minor flood stage on Friday. Crests on these rivers will occur Friday into the weekend. Several other rivers from Snohomish county southward are forecast to reach Action Stage later this week. The lower snow levels with the atmospheric river Thursday through Friday will make river forecasting tough during this event. After a short break it is possible another atmospheric river will move over the area early next week. With the already high running rivers ahead of the event this will be closely watched for another round of possible river flooding.

Felton/15

SEW WATCHES/WARNINGS/ADVISORIES

WA...Wind Advisory from 3 PM Wednesday to 6 AM PDT Thursday for City of Seattle-Downtown Everett / Marysville Area- Eastern Kitsap County-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-Island County-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-Olympia and Southern Puget Sound-San Juan County-Shoreline / Lynnwood / South Everett Area-Southern Hood Canal-Willapa and Black Hills.

Winter Weather Advisory until 6 PM PDT Wednesday 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 Wednesday 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 Watch from late Wednesday night through late Friday night 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 Wednesday 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.

Wind Advisory from 6 PM Wednesday to 6 AM PDT Thursday for Eastern Strait of Juan de Fuca-Grays Harbor County Coast- Northern Washington Coast-Port Townsend Area-Western Strait of Juan de Fuca.

PZ...Small Craft Advisory until 5 PM PDT this afternoon for Grays Harbor Bar.

Gale Warning from 2 PM Wednesday to 2 AM PDT Thursday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca-West Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory until 8 PM PDT this evening for Admiralty Inlet-East Entrance U.S. Waters Strait Of Juan De Fuca- Northern Inland Waters Including The San Juan Islands.

Gale Watch from Wednesday afternoon through late Wednesday night for Admiralty Inlet-Northern Inland Waters Including The San Juan Islands-Puget Sound and Hood Canal.

Small Craft Advisory until 11 PM PDT this evening for Puget Sound and Hood Canal.

Small Craft Advisory until 11 AM PDT 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.

Gale Warning from 11 AM Wednesday to 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.