Wet avalanches

Most avalanche professionals make a hard separation between wet snow avalanches and dry snow avalanches, because they are so different. Much of their mechanics are different, they move differently, and it’s only natural for us to think of them as two altogether separate beasts. But really there’s a continuum between wet and dry avalanches.

Like dry snow avalanches, wet avalanches can occur as both sluffs and slabs. Wet avalanches usually occur when warm air temperatures, sun or rain cause water to percolate through the snowpack and decrease the strength of the snow, or in some cases, change the mechanical properties of the snow. Once initiated, wet snow tends to travel more slowly than dry snow—like a thousand concrete-carrying trucks dumping their loads at once, rather than the hovercraft-like movement of a dry avalanche.

A typical wet avalanche travels at 10 to 20 mph (15 to 30 km/h), but on steeper terrain they can go nearly as fast as a dry avalanche. Probably because not as many recreationists are out on wet snowy days, wet avalanches don’t account for nearly as many avalanche fatalities as dry snow avalanches. However, they still account for a sizeable percentage of avalanche fatalities in maritime climates (mountains bordering oceans), especially to climbers.