North American Public Avalanche Danger Scale

Avalanche danger is determined by the likelihood, size and distribution of avalanches.

Extreme

Travel Advice: Avoid all avalanche terrain.

Likelihood of Avalanches: Natural and human triggered avalanches certain.

Avalanche Size and Distribution: Large to very large avalanches in many areas.

High

Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

Likelihood of Avalanches: Natural avalanches likely; human-triggered avalanches very likely.

Avalanche Size and Distribution: Large avalanches in many areas; or very large avalanches in specific areas.

Considerable

Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

Likelihood of Avalanches: Natural avalanches possible; human-triggered avalanches likely.

Avalanche Size and Distribution: Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Moderate

Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Likelihood of Avalanches: Natural avalanches unlikely; human-triggered avalanches possible

Avalanche Size and Distribution: Small avalanches in specific areas; or large avalanches in isolated areas.

Low

Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Likelihood of Avalanches: Natural and human-triggered avalanches unlikely.

Avalanche Size and Distribution: Small avalanches in isolated areas or extreme terrain.

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