Avalanche Danger
What is the avalanche danger rating and what does it tell me?
Avalanche centers use the North American Public Avalanche Danger Scale to help communicate the potential for avalanches to cause harm or injury to backcountry travelers. The danger rating helps to set the tone for the day through the travel advice associated with the rating. It gives you and initial idea of what to expect and helps to track trends over time.
The avalanche danger combines the likelihood that an avalanche may be triggered with the destructive size of the avalanche as well as the distribution and extent of the avalanche problem across the terrain. In general, the higher the danger rating, the greater the likelihood of a larger, more destructive avalanche.
This danger scale is used by avalanche centers in the US and Canada that use it. It is the rating that is provided on overview maps on avalanche.org and avalanche.ca and is usually the first piece of hazard information presented in an avalanche center's forecast. If there is no rating, it does not mean there is no hazard, only that there is not enough information to provide a rating or that the avalanche center is not currently forecasting for that day or region.
Current statistics tell us that most North American fatal accidents occur when the danger is rated at Considerable, with the percentage of fatalities being similar for Moderate, Considerate, and High (Greene, et al., 2006). This suggests that messaging is effective when the avalanche danger is Low or Extreme. It also suggests that there is still a great deal of uncertainty associated with the Moderate, Considerable, and High danger ratings. This may be because of the terrain understanding, judgment, and decision-making skills required of a group. Danger scale descriptors (i.e. Moderate) alone are not enough to be a useful risk management tool. You also need to have an understanding of avalanche terrain, knowledge of the terrain in which you are traveling, and a high-performing group in order to make sound decisions together in avalanche terrain.
The most successful risk management strategy involves knowing where the problem terrain lies and ensuring your route plan avoids it. The daily danger rating from the advisory helps to quickly compare conditions with nearby regions. Monitoring the danger each day can reveal the trend, suggesting in a general sense whether conditions are improving, staying the same, or getting worse.
