Wet snow (loose snow avalanches)

Characteristics

• The avalanche problem is related to wetting and weakening of the snowpack due to the presence of liquid water. Water infiltrates the snowpack due to melt or rain.
• The problem can occur due to rain, sun, warm temperatures or lack of refreezing of the snowpack at night.
• Avalanches is formed lika a drop, can vary in size from small to large. Runout length can be very long with high water content.

Spatial distribution

• When sun is the main cause, distribution of the problem is mostly depending on aspect and elevation.
• All aspects are affected in the event of rain on snow.
• Releases most often in terrain steeper than 40 degrees, often close to rocks/cliffs.

Trigger mechanisms

• Warming leads to melting and loss of cohesion between snow particles.

Duration

• Hours to days, depending on temperature, precipitation and radiation.
• Rapid loss of stability possible.
• If sun is the cause (typical spring conditions) - the danger increases during the day, most avalanches occur in afternoon when the temperature is higher.
• If rain is the cause, the danger increases when the rain starts.

Identification of the problem

• Usually easy to recognize, the snow surface is wet.
• Wet and soft snow surface, onset of rain, snowballing, pin wheeling and recent loose wet avalanches are signs of instablity.
• Deep foot-penetration is another sign of increased wetting.