The National Weather Service in Seattle issued a barrage of warnings for much of the region, including a rare blizzard warning for the Olympic and Cascade mountains from 6 p.m. Sunday through 6 p.m. Monday.
A high wind warning was issued for the central Washington coast and a high wind watch for the Puget Sound area from midnight Sunday through 10 a.m. Monday.
Gusts could reach as high as 65 mph on the coast and up to 55 mph in the inland areas, and power outages are possible due to falling limbs and trees. Storm-force winds were expected over the Strait of Juan de Fuca, and gale-force winds are forecast over the waters of the Puget Sound.
A coastal flood advisory was issued for high tides and big waves that could produce tidal overflow and flooding near the beaches. The heaviest impact will be on the Washington coast, where 30-foot swells are possible. Tidal overflow and localized flooding also are possible along the Strait of Juan de Fuca and Puget Sound.
In the Olympics and the Cascades, heavy snowfall and high winds are expected to produce blizzard conditions. Up to 3 feet of snow is expected to fall between Sunday evening and Monday evening. Winds could gust up to 60 mph in the passes and from 70 to 90 mph on exposed ridges between Sunday night and Monday evening. Whiteout conditions are expected in the passes.
An avalanche warning also was issued for some areas of the Olympics and Cascades.
National Weather Service meteorologists said the storm will develop rapidly late Sunday as it approaches Western Washington from the North Pacific.
Computer forecast models were generally coming into agreement that a deep low will make landfall near LaPush at around midnight Sunday, then move east and northeast toward the North Cascades.
This track, while not the "classic" major windstorm pattern, will almost certainly bring damaging winds to some areas, the National Weather Service said.
Areas most vulnerable to strong winds include the central coast, the Strait of Juan de Fuca, Admiralty Inlet and possibly the lower Chehalis River valley and southern areas of Western Washington.
The heavily populated Puget Sound region between Tacoma and Everett can expect sustained winds of about 30 to 40 mph, with gusts to 55 mph, the Weather Service said.
Heavy snow is anticipated in the mountains from the incoming system. The Cascades will likely receive another 1 to 3 feet of snow by late in the day Monday, accompanied by high winds.
Heavy rain also will continue for hours across the lowlands of Western Washington from Sunday night through Monday morning.
Precipitation is expected to quickly taper off Monday morning across much of the area, except for the Cascades, where locally heavy snow showers will continue throughout much of the day.
Then snow levels will plummet to near sea level by Monday night as a colder air mass settles over the area. Precipitation in the lowlands is expected to change over to snow or a rain-snow mix - if precipitation is still falling by then.
A Puget Sound convergence zone could form late Monday morning or early Monday afternoon along the King-Snohomish county line. If that happens, there will be a potential for significant snowfall Monday night through Tuesday morning across those lowland areas impacted by the convergence zone.
High temperatures on Tuesday will struggle to get out of the 30s across the lowlands, but precipitation should taper off as higher pressure slowly builds.
Beyond Tuesday, an unsettled weather pattern is expected prevail over the region, but confidence in the details were not very high due to disagreement and lack of continuity among computer forecast models.
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