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New snow

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What?

Characteristics

The avalanche problem is related to current or most recent snowfall. The amount of additional loading by new snow onto the existing snowpack is the crucial factor of the new snow problem. How critical the loading is depends on various factors such as air temperature, wind or characteristics of the old snow surface.

Expected avalanche types

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

Where?

Spatial distribution

In general, a widespread presence and often on all aspects.

Position of the weak layer in the snowpack

Usually between new snow and old snow, i.e. close to the interface to the old snow surface, sometimes in the new snow layers and occasionally slightly below in the old snowpack. In the latter case, the problem “persistent weak layers” additionally prevails.

Why?

Release characteristics

  • Dry-snow slab avalanches: Additional load due to snowfall on existing weak layers (old snow surface or below) or newly created weak layers (within the new snow)
  • Dry loose snow avalanches: Lack of cohesion between the new snow particles

When?

Duration

Typically during snowfall and up to a few days after.

How to manage?      

Identification of the problem in the field

The new snow problem is fairly easy to recognize since it affects most of the terrain. Consider critical amounts of new snow and recent avalanche activity.

Travel advice

  • Dry‐snow slab avalanches: Wait until the snowpack has stabilized and the weak layer has gained strength.
  • Dry loose snow avalanches: Danger of being carried by small releases is more important than danger of burial. Consider consequences in steep terrain.

Typical accident

Meierhofer Tälli, Davos (GR), 17 February 2012