Avalanche Danger Beyond 'Extreme' in Cascades

PORTLAND -- Experts say the danger of avalanches is great in the Cascade Range from Central Oregon north to Mount Rainier.

They say extreme conditions expected Thursday in the mountainous backcountry are a result of an unusually weak snowpack, high winds and new snow.

"There's nothing beyond extreme in our lingo," said Mark Moore, director of the Northwest Avalanche Center in Seattle. "It is a recipe for a very dramatic increase in danger."

Early Tuesday, the center forecast "high risk" above 6,000 feet in the backcountry in the Mount Hood area, meaning travel along avalanche terrain would likely trigger slides.

The dangers decreased by late afternoon but were expected to rise again.

With another 2 to 3 feet of snow expected early Thursday in backcountry areas, conditions are ripe for slab avalanches of the kind that buried a group of 11 snowmobile riders over the weekend in British Columbia, killing all but three.

Snow slides in a slab avalanche when a stronger overlying layer of snow breaks loose from a weaker layer.

"We got so many feet of snow and multiple snowfalls in multiple layers, I'm not surprised that we're under an avalanche warning," said Peter Frenzen, spokesman for the Mount St. Helens National Volcanic Monument. "If something crosses the surface and sets one in motion, watch out."

During the last avalanche season, from November into April, 52 people died in avalanche-related deaths in the United States and Canada.

Moore called the 2007-08 total a "modern-day record."

"This season is shaping up in a similar way," he said. "This is not a trivial snowpack situation. It can be very brutal."