STEVENS PASS — Heavy snow at Stevens Pass is forecast to continue through Thursday and the National Weather Service in Seattle has issued a winter storm warning for the mountain passes.

As much as a foot of fresh snow could fall by tomorrow morning and another foot could accumulate by Thursday night, forecasters said.

People headed to the pass should plan for extra time and to drive carefully, officials said.

Drive east toward Stevens Pass and road conditions likely will change at every turn of U.S. 2.

On Tuesday, there was slush on the road near Gold Bar, snow and ice at Index and by Skyko­mish, it was a full-on blizzard.

The rapidly changing conditions require drivers to pay close attention and slow down, Washington State Patrol trooper Kirk Rudeen said.

“If they’re heading up to go skiing — the mountains aren’t going anywhere, the snow’s not going to melt before you get there — take a few extra minutes and slow down,” Rudeen said.

During bad winter weather, troopers often are busy going from accident to accident, he said.

Narrow and winding, U.S. 2 can be dangerous. Cars, sport utility vehicles and trucks can lose control and either end up in the path of oncoming traffic or in a ditch.

“There’s so little room for error, and it’s not very forgiving,” Rudeen said.

Four-wheel-drive cars and SUVs may help drivers get started, but they provide no help in stopping on snow and ice.

“Even if they have a four-wheel-drive vehicle, the laws of physics still apply,” Rudeen said.

All vehicles should carry chains. Even with traction tires and all-wheel drive, if it feels like chains are needed, put them on, he said.

As much as 2 feet of fresh snow is forecast to fall at Stevens Pass by this morning, said Dennis D’Amico, a meteorologist with the National Weather Service in Seattle.

More snow is expected in the Cascade Range as winter storms continue to pummel Western Washington, he said.

Snow fell all the way down to sea level Tuesday. A few inches accumulated in some lowland areas. Everett schools delayed opening and cancelled some kindergarten classes Tuesday.

Temperatures in the lowlands are forecast to rise into the 40s today and Thursday, D’Amico said.

“There’s no snow in the forecast for the next seven days” in the lowlands, he said.

Changing weather conditions and additional heavy, wet snow in the mountains are adding to an already unstable snow pack causing extremely dangerous avalanche conditions in the mountains, said Kenny Kramer, an avalanche forecaster with the Northwest Weather and Avalanche Center in Seattle.

Since December, three people from Snohomish County and nine people statewide have died in avalanches, making this year the deadliest in modern history, experts said.

On Friday, a 13-year-old Mukilteo girl died near Lake 22 off the Mountain Loop Highway. An Everett woman died snowmobiling New Year’s Day near Mount Baker and a Brier man died before Christmas while snowshoeing on Mount Rainier.

State Department of Transportation crews worked to keep mountain passes safe, using explosives to clear avalanche danger.

“They do a really good job on U.S. 2, but there are times when the weather moves in and they just can’t keep up,” Rudeen said. “It’s how quickly things can change up there.”

Reporter Jackson Holtz: 425-339-3437 or jholtz@heraldnet.com.