Heavy rain, strong winds, mountain snow, flooding to blast Western WA

Mother Nature has a laundry list of winter weather conditions she is eager to deliver to Western Washington.

Heavy rain and strong winds, of course. Some river flooding and coastal flooding, because why not? Mountain snow and even Western Washington’s first blizzard warning since 2012, a masterful 180 following December’s record warmth.

A flurry of warnings, watches, hazards and advisories will accompany this week’s active weather, which could even end with snow in Seattle.

How, you may be wondering, can Mother Nature do it?

A “very potent weather system” is responsible, said Dustin Guy, a meteorologist with the National Weather Service in Seattle.

Sunday came and went as the quietest day of the week, with lingering showers leaking into Monday, when the week’s first big weather-maker barged into the region.

For most of us, Monday was expected to be increasingly rainy, while the mountain passes were expected to pick up as much as a foot of fresh snow, according to the weather service.

Some spots, around Hood Canal, north of Everett and along the Cascade foothills and valleys, saw wet snow or a rain/snow mix Monday before rain prevailed.

Shortly before 1:30 p.m. Monday, eastbound Interstate 90 closed at milepost 47, about 5 miles west of the summit, due to multiple crashes. Westbound travel remained unaffected.

Over 4,000 Seattle City Light customers in North Seattle were without power Monday afternoon, too. By Monday evening, the number of customers impacted was reduced to about 250.

A stronger system was expected to follow into Tuesday, bringing more rain and 40-50 mph winds across most of Western Washington. The strongest gusts will blow in the mountains and along the northern coast and into the San Juans and Whidbey Island, where there is a 50% chance for gusts exceeding 60 mph.

There is a wind advisory in effect through 10 p.m. Tuesday across much of the lowlands of Western Washington, with wind speeds and gusts varying by location. The Seattle area, for example, will see 25 to 35 mph winds with gusts up to 45 mph.

“It’s going to be a very windy period coming up here starting Monday night and taking us all the way through Tuesday,” Guy said.

Those strong winds (50-60 mph) in the mountains, combined with a healthy dumping of 2 to 5 feet of snow in elevations above 2,000 feet, will create periods of whiteout and near-zero visibility Tuesday, the weather service said.

A winter storm warning for up to 12 inches of snow will last through 4 a.m. Tuesday in both the Cascades and Olympics.

Then, a blizzard warning ( you read that right) for up to 30 inches of snow and winds gusting as high as 65 mph begins 4 a.m. Tuesday and lasts until 10 a.m. Wednesday.

Blizzard warnings are rare in Western Washington – the last one was over a decade ago – and they require a combination of blowing snow, 35-plus mph winds and quarter-mile visibility for three hours or more, according to the weather service.

“Needless to say, the heavy snow combined with gusty winds is going to make very treacherous traveling conditions in the mountains,” Guy said.

The Washington State Department of Transportation and Washington Emergency Management are urging drivers to avoid traveling through the passes.

Snow elevations will be higher along the south slopes of the Olympics, and thus heavy rain will force sharp rises on Mason County’s Skokomish River. Minor flooding is possible Monday night or Tuesday, the weather service said.

Down near the surface, precipitation will fall in the form of 1 to 2 inches of rain on Tuesday, with the highest amounts at the coast. As the system churns offshore, seas will build, creating high surf conditions (breaking waves of up to 30 feet) and potential coastal flooding.

Only minor coastal flooding is forecast at Westport, Friday Harbor and Port Angeles on Tuesday, but there may be increased tides, so there are coastal flood watches in effect for a potential 2 to 3 feet of coastal flooding at the coast and in the San Juans and Admiralty Inlet.

Heavy mountain snow and strong winds will continue into Wednesday, with both easing toward the afternoon. Seas will subside, but the weather service is monitoring high tides and possible minor tidal overflow with king tides.

Then, Mother Nature’s real fun begins.

Offshore winds and a stream of cool air flooding the region from the north will force temperatures down in the latter half of the week.

“There is still a lot of uncertainty in how cold we get,” the weather service said Sunday evening, but even lows in the 20s – the most likely scenario – would be “much below normal and cool enough for snow.”

Chances for lowland snow had increased slightly by Monday, with a 40% to 60% chance for at least 1 inch of snow between Thursday and Saturday, and a 30% chance for 2 inches or more, according to the weather service.

But forecasting lowland snow in Western Washington “is extraordinarily difficult because all the ingredients really have to come together perfectly for that to really pan out,” Guy said Monday morning. “We certainly are looking at colder air coming in,” he continued, but any snowfall estimates will be solidified over the next few days.