SEATTLE -- Wet, heavy snow toppled trees, cut power and delayed classes at a number of school districts Monday in the latest winter assault on the region.

Get the complete list of school delays and closures here.

Up to 4 inches of snow -- wetter and heavier than December's snowfall -- caused trees and branches to come crashing down onto power lines. It hit especially hard in Burien and the southwest part of Seattle.

Seattle used salt on streets for the first time in about a decade under a new policy adopted after complaints about slow snow removal in December.

Seattle City Light said 19,000 of its customers were in the dark at one point, but power was restored to all but about 100 of them by midday Monday.

Near Seattle's Volunteer Park, work crews cut up a tree that fell onto Metro trolley lines, blocking the street for hours. Nearby, another tree fell in chunks onto a road.

VIDEO: Branches Fall On House During Heavy Snow

Metro said most of its buses were on regular routes, but some had chains on.

In Everett, reporter Jeff Dubois said there was snow on the ground, with slush underneath. At one point Sunday night, snow was falling there at the rate of an inch an hour.

VIDEO: Commuters Surprised By Blast Of Snow

In the North Highline neighborhood west of Boeing Field in Seattle, reporter Rick Price said there's more snow than any other neighborhood he saw during an overnight tour that included Issaquah and other parts of Seattle.

"It is very slick," he said, with several inches of snow on the ground in the southern part of the city, especially on side streets.

Sea-Tac Airport was operating normally Monday after snow caused delays Sunday night.

Sea-Tac officials said only one runway was open while they plowed the other two during the snow. KIRO 7 Eyewitness News anchor Steve Raible was supposed to land at Sea-Tac Sunday night but his plane was rerouted to Spokane.

Some other planes were rerouted to Bellingham.

Eastbound Interstate 90 at Snoqualmie Pass reopened Monday afternoon after both directions were closed by heavy snow and avalanche danger at 11 p.m. on Sunday.

Westbound I-90 remains closed between North Bend and Ellensburg. The Transportation Department said it will reopen the pass when it has the avalanche danger under control.

A winter storm warning is in effect for the west slopes of the north and central Cascades above 2,500 feet until 6 a.m. Tuesday.

Forecasters said another 6 to 12 inches is likely by late Monday night, bringing the storm total to 1 to 2 feet.

In addition, avalanche watches and warnings are in effect for areas of the mountains through Monday morning.

"Natural or human triggered avalanches should become likely by early Monday morning and travel in avalanche terrain is not recommended Monday," said a statement from the National Weather Service.