BANFF, Alta. — The North American public avalanche danger scale is determined by the likelihood, size and distribution of avalanches.
Here's an explanation of each level:
Extreme: Avoid all avalanche terrain. Natural and human-triggered avalanches certain. Large to very large avalanches in many areas.
High: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Natural avalanches likely; human-triggered avalanches very likely. Large avalanches in many areas, or very large avalanches in specific areas.
Considerable: Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential. Natural avalanches possible; human-triggered avalanches likely. Small avalanches in many areas, or large avalanches in specific areas, or very large avalanches in isolated areas.
Moderate: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Natural avalanches unlikely; human-triggered avalanches possible. Small avalanches in specific areas, or large avalanches in isolated areas.
Low: Generally safe conditions. Watch for unstable snow on isolated terrain features. Natural and human-triggered avalanches unlikely. Small avalanches in isolated areas or extreme terrain.