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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