New snow (slab avalanches)

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.
• Critical snow amount is often 30-50 cm but how critical the loading is depends on various factors such as temperature or characteristics of the old snow surface.
• The slab is often soft and easy to trigger.
• Avalanche size is often underestimated, varies in size from medium to very large.

Spatial distribution

• Generally widely present and often in all aspects.
• Releases typically in terrains from 30 degrees and steeper.
• Can release in all types of terrain, but most often above the treeline.

Release characteristics

• Bonding processes in the new snow leads to formation of a soft slab (radiation, vind, temperature).
• Additional load due to snowfall eads to failure in existing or newly created weak layers.

Location of weak layer in the snowpack

The weak layer is sually at or close to the interface to the old snow surface. If the weakest layer is in the old snowpack another avalanche problem wil be chosen, i.e. Persistent weak layer.

Possible weak layers

1. Buried weak layer of new snow
2. Poor bonding between crust and overlying snow

Duration

• Typically during snowfall and up to a few days after.
• Stabilizes often fast, depending on temperature and radiation.

Identification of the problem

• The new snow problem is fairly easy to recognize.
• Watch out for new snow amounts and recent avalanche activity.
• Be aware of slight weather changes affecting new snow conditions.
• Danger signs:
• The new snow bonds into a soft slab
• Cracking
• Recent avalanches