Winter storm warnings were issued throughout Western Washington on Sunday as significant snowfall is expected in low-lying areas and the Cascades.
The National Weather Service issued the warnings after forecasts showed between 3 and 6 inches of snow falling in the South Sound lowlands through 4 p.m. Monday (Feb.6).
The snowfall is expected to increase in intensity and begin to stick Sunday evening, Weather Service meteorologist Johnny Burg said. It’s a product of a colder air mass interacting with the typically moist Northwest winter weather.
“Basically, we’re going to have air cold enough where we’re going to see snow, and there’s just enough moisture in the air, and so we’re going to see a bunch of it,” Burg said.
Low temperatures are expected to hover around freezing Sunday night and into Monday, where highs are forecast in the high 30s. Lows are expected to again drop below freezing Monday and Tuesday nights before warmer weather turns any lingering snowflakes back into rain.
The Cascade foothills are expected to see up to 8 inches of snow from the storm, Burg said. The Cascades are expected to see 20 to 30 inches of snow through Monday afternoon as the snow level, currently at 1,500 feet, is expected to fall below 1,000 feet.
A winter storm warning for the Cascades advises people to only travel Snoqualmie and White passes in an emergency.
Crashes closed Interstate 90 eastbound near Snoqualmie Pass for about two hours early Sunday, according to the Washington state Department of Transportation, then it closed again for a brief period about 1 p.m.
Snoqualmie Pass also had to be closed Saturday afternoon for avalanche control. The Northwest Avalanche Center raised the risk of human-caused avalanches to high Sunday.
An earlier winter weather advisory had only forecast 1 to 3 inches of snowfall after early Sunday rain transitioned to snow.
But snow was already falling in much of the South Sound by 9 a.m., prompting the Weather Service to upgrade the advisory to a winter storm warning.
“Roads and sidewalks will be snow-covered and slippery,” the Weather Service warning reads. “Travel will be very difficult … especially during the Monday morning commute. Delays may be significant.”
University of Washington meteorologist Cliff Mass wrote Sunday morning that other forecasting models paint an even whiter picture for the region than the Weather Service forecasts.
“I have studied Northwest snowstorms for years, and the situation is not optimal for a big snow event, but it is close enough and the models are now insistent enough that significant lowland snow from Seattle to Portland looks highly probable,” Mass wrote.
The European Center weather model, which Mass considers the best available, shows up to 10 inches falling in Tacoma through Monday night, with even more in Olympia and East Pierce County.
There is a lot of variance in the forecast, Mass wrote — with there being either a 25 percent chance of a dusting of snow or a foot of snow falling in Seattle.
“These are similar probabilities as were given for the election of President Trump — so they are not negligible,” he wrote.
Northwest Trek Wildlife Park near Eatonville closed Sunday due to icy conditions and is expected to reopen Friday, according to Metro Parks Tacoma.