textproduct: Seattle/Tacoma

SYNOPSIS

A frontal system will continue to cross the region today, bringing an additional round of breezy winds, lowland rain, and mountain snow to western Washington. A low pressure system will track northward along the coast on Wednesday, bringing in another round of precipitation and potentially strong winds. Unsettled conditions will continue into Thursday and beyond as troughing persists over the western US.

SHORT TERM /TODAY THROUGH WEDNESDAY NIGHT/

A frontal system will continue to shift inland across western Washington this afternoon and evening, bringing another round of lowland rain, mountain snow, and breezy winds. Wind gusts have peaked for the day along the Pacific coast, and snow is beginning to wind down over the Olympics. As the frontal system continues eastward, southerly winds will continue to increase across the interior, reaching 35 to 45 mph with isolated higher gusts along the northern Olympic Peninsula coastline through Whidbey Island northward. Precipitation will also continue to spread eastward along the front through the evening with snow levels near 2000-2500 feet. Snowfall rates will top out over the Cascade Passes later this afternoon and evening, with an additional 3 to 6 inches of snow accumulation expected for Snoqualmie and Stevens Passes. Post-frontal showers will continue into Tuesday morning, especially over the Olympics and Cascades, with some drying and brief sun breaks for the lowlands by Tuesday afternoon.

The next incoming weather system will intensity off the coast of California late Tuesday and shift northward across western Washington on Wednesday. While forecast models continue to struggle with the exact track of this surface low feature, it poses a risk of a low probability, high impact wind event alongside additional precipitation. East to southeast winds are likely to pick up during the morning Wednesday along the western slopes of the Olympics and Cascades, followed by a surge of stronger southerly winds during the day Wednesday. While ensemble mean wind gusts continue to range generally between 30 to 40 mph across much of western Washington, a high end scenario could bring sudden winds reaching 60 mph or more if the low pressure system tracks in the vicinity of western Washington. Confidence will increase as more high resolution forecast data becomes available as the event draws closer. It will remain extremely important to continue to monitor the evolving forecast over the next few days, especially given the antecedent soil moisture which may allow for heightened impacts at slightly lower wind speeds. In addition to the potential gusty winds on Wednesday, The lowlands will see up to a quarter inch of rain while elevations above 2500 feet will see a few more inches of snow accumulation.

LONG TERM /THURSDAY THROUGH SUNDAY/

Lighter precipitation is on track to spread into western Washington on Thursday and Friday as the low pressure system exits to the north. High pressure is then forecast to build of the western US coast and build inland towards the Pacific Northwest, helping to shift the bulk of any incoming precipitation northward. Conditions may dry out across much of the lowlands by next weekend, with lowland rain and mountain showers along the British Columbia border. While unsettled and cooler conditions will persist, signals for another incoming atmospheric river system towards the end of next week have decreased, with models focusing this potential system northward into Canada.

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AVIATION

Southwest flow aloft will continue into Tuesday with a frontal system and associated upper trough moving onshore later this evening. Ceilings will lower to MVFR at times in rain late this afternoon into this evening. Precipitation will diminish overnight with areas of MVFR continuing. A return to VFR is expected across much of Western Washington on Tuesday morning. Gusty southerly surface winds will accompany the front before easing overnight.

KSEA...Ceilings will lower to MVFR in rain at times late this afternoon into the evening. MVFR ceilings will remain in place at times overnight before lifting back to VFR again Tuesday morning. Surface winds southerly 15 to 25 knots easing to 8 to 12 knots overnight.

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MARINE

A frontal system will move onshore late this evening. A weak surface trough will remain over the coastal waters into Tuesday. Considerable uncertainty remains in the forecast for midweek with the path and strength of a secondary trough. A broad surface trough well to the south of the area and high pressure over the interior of British Columbia will lead to a period of northerly flow late in the week.

Seas are expected to briefly drop below 10 feet midweek before building back to double digits again Friday onward.

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HYDROLOGY

Rivers across western Washington continue to trend downward as precipitation across the region lightens up. A frontal system will bring in generally half an inch of rainfall or less through Tuesday with snow levels near 2000-2500 feet. No significant rises are expected on area rivers, with the Skokomish River being the only river to remain in flood stage until Wednesday.

Additional rainfall throughout the week is not expected to cause any additional rises to area rivers, and flooding outside of the Skokomish River in Mason County is not expected over the next 7 days.

Additionally, the threat of landslides has decreased across western Washington.

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SEW WATCHES/WARNINGS/ADVISORIES

WA...Wind Advisory until 7 PM PST this evening for Island County- Lowlands of Western Skagit and Northwestern Snohomish Counties-Lowlands of Western Whatcom County-Port Townsend Area-San Juan County.

Winter Storm Warning until 10 PM PST this evening for Cascades of Whatcom and Skagit Counties.

Winter Weather Advisory until 10 PM PST this evening for Olympics.

Wind Advisory until 4 PM PST this afternoon for Grays Harbor County Coast-Northern Washington Coast.

PZ...Small Craft Advisory until 10 AM PST Tuesday for Grays Harbor Bar.

Small Craft Advisory until 4 AM PST Tuesday for Admiralty Inlet-Central U.S. Waters Strait Of Juan De Fuca-Puget Sound and Hood Canal-West Entrance U.S. Waters Strait Of Juan De Fuca.

Gale Warning until 10 PM PST this evening 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-East Entrance U.S. Waters Strait Of Juan De Fuca-Northern Inland Waters Including The San Juan Islands.

Small Craft Advisory from 10 PM this evening to 4 PM PST Tuesday 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- East Entrance U.S. Waters Strait Of Juan De Fuca.