Avalanche Problems due to new snow and/or wind

When the weather forecast calls for new snow and/or wind, or when backcountry reports and weather station data show prolonged wind or new snow, you can expect loose dry, storm slab, wind slab, and cornice avalanche problem types. Familiar with avalanche problem types? Skip ahead to check your understanding.

David Dellamora

Dry Loose Avalanche

Dry loose avalanches are the release of dry unconsolidated snow. These avalanches typically occur within layers of soft snow near the surface of the snowpack. Loose-dry avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs. Loose-dry avalanches can trigger slab avalanches that break into deeper snow layers.

Chris Meder

Storm Slab Avalanche

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Ben Pritchett

Wind Slab Avalanche

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near- surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Tom Carter

Cornice Fall

A Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

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For a quick reference summary of all the problem types bookmark this page: https://avalanche.org/avalanche-encyclopedia/#avalanche-character

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