online avalanche course

Loose wet avalanches

Like loose dry avalanches, loose wet avalanches are usually confined to surface layers, and are therefore often small. However, because of their high density, loose wet avalanches contain greater mass and are much more difficult to fight against than loose dry avalanches. They contain cohesion-less wet slushy snow, and like loose dry avalanches, they start from a point and gather mass progressively in a fan-like shape. They are also sometimes called "point releases.”

Loose wet avalanches are most common in late winter or spring, and are caused by warm temperatures, strong solar radiation, rain, or some combination of these factors. In periods of significant, prolonged melt or rainfall loose wet avalanches can become large and destructive but this usually occurs in conditions where recreational activities are highly undesirable or impossible. They require sufficiently steep slopes to initiate, generally at least 35 degrees and typically 40 degrees or more, and are often in rocky terrain.

Loose wet avalanches often occur in diurnal cycles due to varying solar radiation rates and temperature fluctuations. The ease of triggering, size, and power of loose snow avalanches can often be assessed by observing current and recent avalanche activity. Slopes can be tested by applying a trigger such as a rock, small cornice, or even a snowball. Early signs of instability include pinwheeling and snowballing. A very firm, smooth layer, such as a crust, below the loose snow on the surface tends to increase the likelihood of wet loose avalanches.

View larger image Snowballing | Photo: C. Campbell
View larger image Loose wet avalanches | Photo: R. Siggers
View larger image Pinwheeling | Photo: B. Jamieson

Managing your risk

For more information on how loose wet avalanches can hurt you and how you can manage the problem see: Good Travel Habits - Reducing the Risk in the Field

Wet slab avalanches