Key takeaways
- A wet avalanche is a slide of wet, water-saturated snow weakened by liquid water.
- Triggers: warming, rain, or snowmelt percolating into the snowpack.
- Slower-moving than dry slides but dense, heavy, and very destructive — hard to escape.
- Warning signs: rollerballs/pinwheels, slushy snow, and daytime warming or rain.
This is general educational information, not avalanche-safety training. Avalanches are deadly — get formal avalanche education, carry rescue gear, and check the local forecast.
What a wet avalanche is
A wet avalanche is an avalanche of wet, water-saturated snow, triggered when liquid water — from warming, rain, or melt — percolates into the snowpack and weakens the bonds between snow grains. Unlike dry slides of cold, light snow, wet avalanches are dense, heavy, and concrete-like.
What causes them
Liquid water in the snowpack: spring warming and strong daytime heating, rain on snow, and rapid melt. As water percolates down, it lubricates and weakens the bonds between grains and at weak layers until the saturated snow loses cohesion and slides — often later in the day as warming peaks.
On a warm spring morning, a ski tourer notices rollerballs spinning down a sunny slope and their skis punching into slushy, unsupportable snow — clear wet-avalanche warning signs — so they cut their tour short and descend before the midday heat destabilizes the slopes further.
Warning signs
- Rollerballs / pinwheels — small balls of wet snow rolling downhill.
- Slushy, unsupportable snow — you sink in deeply.
- Water running on or in the snow; recent rain on snow.
- Rapid daytime warming with little overnight refreeze.
When these appear, get off and out from under steep slopes — often by descending earlier in the day. Wet slides are one avalanche type alongside the slab and loose-snow avalanche.
The bottom line
A wet avalanche is a slide of heavy, water-saturated snow, triggered when warming, rain, or melt weakens the snowpack. Slower than dry slides but dense and very destructive, it's hard to escape. Watch for rollerballs, slushy unsupportable snow, and rapid daytime warming — and get off and out from under steep slopes before the snow heats up, often by descending early in the day.
Frequently asked questions
What is a wet avalanche?
A wet avalanche is an avalanche made up of wet, water-saturated snow. It happens when liquid water — from warming temperatures, rain, or melting — gets into the snowpack and weakens the bonds holding the snow together, causing the wet snow to release and slide. Unlike dry avalanches of cold, light snow, wet avalanches involve heavy, dense, sodden snow.
What causes wet avalanches?
Liquid water in the snowpack. The main triggers are spring warming and strong daytime heating (especially the first hot, sunny days of spring), rain falling on snow, and rapid melt. As water percolates down through the snow, it lubricates and weakens the bonds between grains and at weak layers, until the saturated snow loses cohesion and avalanches. They often happen later in the day as warming peaks.
What are the warning signs of wet avalanche danger?
Key signs include rollerballs or 'pinwheels' (small balls of wet snow rolling down slopes), snow becoming slushy and unsupportable (you sink in deeply), water running on or in the snow, recent rain on snow, and rapid daytime warming with little overnight refreeze. When the snow turns wet and mushy and natural rollerballs appear, wet avalanche danger is rising — a cue to get off and out from under steep slopes, often by descending earlier in the day before the snow heats up.
Sources
- Avalanche types & safety — American Avalanche Association
- Avalanche awareness — Utah Avalanche Center