WENATCHEE — One major mountain pass in Washington was completely shut down Tuesday, and part of another. The reason: Avalanches, brought on by fast accumulations of new mountain snow.

“We literally went from almost no avalanche danger to now, in a very short amount of time, having an avalanche warning,” says Kenny Kramer, an avalanche meteorologist with the Northwest Avalanche Center in Seattle. “So that’s how quickly things can change.”

The Northwest Avalanche Center in Seattle tracks avalanche danger throughout the region, and on Tuesday, that danger was high throughout most of the Cascade range and foothills.

Snowfall collects in layers, and their consistency changes depending on temperature and other factors. Kramer says the layers underneath this new snowfall aren’t strong enough to support it, and that can easily lead to avalanches.

“Prior to this storm cycle, we had some very warm weather with very high freezing levels, and once that froze, that left a hard crust layer,” Kramer says. “And then we had some weak, very cold snow, fall on that, and that cold snow on that crust is now being loaded by two to four feet of storm snow. And that whole package is really what’s leading to the high danger right now.”

The state Department of Transportation closed Snoqualmie Pass on Monday evening from North Bend to Ellensburg, citing multiple accidents and snowslides, and snow accumulation of 53 inches in 48 hours. On Highway 2 outside Leavenworth, a pair of slides closed a 15-mile section of the highway about 11:40 p.m. Monday, and rerouted traffic to the Chumstick Highway. DOT spokesman Jeff Adamson says crews were using heavy equipment to clear those obstacles.

“Because of, frankly, the nature of that canyon, we’re not allowed by Labor and Industries to even attempt any avalanche control activity in the canyon except in daylight hours,” Adamson says. “So all we could do when that happened early this morning was pull the gates closed at both ends, and tell the trucks to turn around.”

Until this year, DOT posted former Army tanks along the passes to shoot ordnance and trigger preemptive slides in the avalanche zones. Those tanks were taken out of service and returned to the Army after last winter; to shoot charges, DOT now uses howitzers, like these shown operating on the North Cascades Highway. Crewmembers also deliver explosives by helicopter, snowmobile and skis.

Jefferson Robbins: 679-7013 

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