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Snowdrifts

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What?

Characteristics

The avalanche problem is related to wind‐drifted snow. Snow can be transported by wind with or without a concurrent snowfall.

Expected avalanche types

  • Dry‐snow slab avalanches
  • Natural and human triggered avalanches

Where?

Spatial distribution

Highly variable but typically on leeward sides in gullies, bowls, near distinct changes in slope angle, behind ridgelines or other wind‐sheltered locations. More common above treeline.

Position of weak layers in the snowpack

Usually at the transition to the old snow surface or within the windslab layer due to variation in wind speed and variation during storm cycle, but occasionally also deeper in the old snow cover.

Why?

Release characteristics

Wind‐drifted snow is an additional load on a weak layer and builds a slab which is particularly prone to support crack propagation.

When?

Duration

Wind‐drifted snow can evolve very quickly. The problem lasts typically during the snowdrift event, up to a few days at most, depending on snowpack evolution.

How to manage?

Identification of the problem in the field

If not hidden by new snow the wind‐drifted snow problem can be recognized with training and good visibility. Consider wind signs and locate deposits. Typical clues: snowdrift deposits, recent avalanche activity and sometimes shooting cracks or whumps. However, it is often hard to determine the age of wind signs and wind signs do not necessarily imply an avalanche problem (e.g., in absence of a weak layer).

Travel advice

Avoid snowdrift deposits in steep terrain, in particular in areas where the snow cover changes from thin to thick or from hard to soft.

Typical accident

Juferhorn, Avers (GR), 3 January 2012