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Hidden avalanche danger remains and could get worse when spring melt settles in

Posted at 9:08 PM, Mar 21, 2019
and last updated 2019-03-22 13:17:56-04

DENVER -- Spring is not erasing the threat of avalanches and this time, the danger is hidden under layers of snow.

The Colorado Avalanche Information Center (CAIC) is warning about a problem created when a layer of weak snow is buried under a thick slab of hard snow that forms after a series of storms, like the significant snowfall earlier this month. The technical term is 'deep persistent slab' and although these avalanches can be difficult to trigger, they are usually deadly.

“We are moving away from these really big snowstorms that caused us all this trouble but the weak snow is still in the snowpack and it’s still possible to trigger avalanches there," said Ethan Greene, Director of the Colorado Avalanche Information Center.

Conditions were similar in April 2013, when a snowboarder triggered a slide on Ptarmigan Hill near Vail Pass. Greene says it's a classic example because stronger snow in the upper part of the snowpack was layered on top of weak snow. He said the snowpack was so thick the slide wasn't triggered right away.

"On that particular day we figured there were about 20 people that rode over that slope before one person hit the right spot and the whole thing avalanched in a very large slide that did a lot of damage to the forest, broke a lot of trees and unfortunately killed one person," said Greene.

As Greene explains, it's all about the layers of snow and where those layers exist in the terrain. He says the current situation is due in part to winter storms in early March and the progression of snow throughout the entire season.

"Somebody walking on the snow in the right place at the wrong time can trigger a catastrophic event," said Greene.

As the spring melt settles in, he says the danger won't go away and could actually get worse. He believes we could see a different type of problem when water is introduced into the snowpack.

"So just when the snow is starting to melt it can be unstable. We start to get water down into those deeper snowpack layers and we could see some very large wet avalanches this spring," said Greene.

Greene encourages everyone to check current avalanche conditions and plan your activities accordingly. He says conditions vary in different parts of the state and depending on the type of terrain. If you're looking for more information on 'deep persistent slabs', The Colorado Avalanche Information Center offers this explainer.