Warning: critical avalanche situation in large parts of the Alps

meteomorris

Peak season started in the Alps and lots of Europeans will go skiing and snowboarding the next couple of weeks (the last week of February will be extremely busy). For most of the tourists it will be the first time they'll go skiing or snowboarding this winter. Most parts of the Alps were still green during Christmas, but now they're covered in snow. But there's less snow than normal. The snow cover in large parts of the Alps is (much) thinner than normal. The combination of a thin snow cover, crowds in the Alps and trends such as ski touring, split boarding and the desire of many skiers to experience authentic adventures in the backcountry could bring some troubles.

Troubles? Why?

The start of the season was exceptionally dry in the Alps. With the exception of early November almost no snow came down in the Alps. The snow that came down early November disappeared on many slopes due to the sun. But the sun wasn't powerful enough to melt the snow on north-facing slopes above 2,200 meters in that period of the year. Therefore, there is a layer with old snow in the snow cover on northern slopes. New snow fell on top of that layer in the beginning of January.

Thin snow cover in the Arlberg region mid december

So why is that a problem? Well, the snow in that old layer turned into facets. Those facets have absolutely no cohesion with each other. They're basicly lying around like single snow flakes. If another layer of snow falls on top of this layer with faceted snow, the two layers doesn't bond. So, there's a massive layer of snow on top of a layer with faceted snow, that functions as ball bearings. Put some pressure on it, and chances are that the top layer will break. Add a slope that's steep enough to this lethal cocktail and you trigger an avalanche.

Faceted snow (source: data.avalanches.org)

Normally (as in: when there's more snow in the Alps), this old layer isn't much of a problem, simply because it's deeper in the snow cover and there's little chance that you hit that old layer while skiing or snowboarding. But that's different this winter. The pressure of a single skier or snowboarder is enough to trigger an avalanche. Expect for the Italian Piedmont, the snow cover is much thinner than normal in large parts of the Alps. Unfortunately, that weak layer is also present in the Piedmont.

Is it still a problem?

Yes, it is. Avalanches in the Alps already claimed the lives of 31 people this season and at least a third of those fatal accidents happened because of this old layer. We've received reports from Austria, Switzerland and France where avalanches came down last weekend.

Avalanche in the Aravis (source: data.avalanches.org)

Avalanche in Valfréjus close to Piste Le Jeu (source: data.avalanches.org)

How long will it remain a problem?

This layer will remain a problem as long as the snow cover is too thin. So we need much more snow. And because there won't be any precipitation coming down in the Alps the next couple of days, this warning is very useful. We definitely need at least two big dumps.

Where can we find this old layer?

This old snow layer can be found especially on shaded slopes above the tree line (that's above 1900 to 2200 meters). It's situated deep in the snow cover on north faces, but also on steep east and west faces. Always check the local avalanche forecast, because it'll be mentioned if it's there.

How do you recognize this old layer?

Well you don't. It's hidden deep in the snow cover and is not visible with the naked eye. The snow cover looks nice, but carries a potential danger. Our human brain won't be triggered that there's a danger (simply because it's invisible). You have to dig a snow pit to actually see the old layer of snow.

What can you do about it?

If you don't have the right knowledge, you shouldn't ski or snowboard off-piste. Simple as that. Even with the right knowledge you should ride very conservative lines the next couple of weeks. Don't ride any steeper than the risk reduction methods tell us. With avalanche danger level 3 (Considerable) you shouldn't ride steeper than 35 degrees and maybe even less steep. Another good thing to do is not to ski off-piste above the treeline. There's plenty of snow below the treeline in lots of regions in the Alps and the problem with the old snow layer is not that significant below the treeline.

So pay attention and keep asking yourself the following questions:

  • Do you have the right knowledge?
  • Do you (and the other riders in your group) have the gear (avalanche beacon, shovel and probe)?
  • Have you read the local avalanche forecast?
  • Do you know which parts of the mountain you have to avoid that particular day to minimize the risk?

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