Avalanche Risk Scale
Every modern ski resort will issue notices (bulletins) indicating the level of Avalanche Risk for each day. These risk levels are generally quoted from a five-point scale of increasing risk (of avalanche).
If you plan to ski or snowboard off-piste it is essential that you understand the Avalanche Risk Level for each local area and plan your skiing accordingly.
Five Levels of Avalanche Risk
The following Table summarises the five levels of Avalanche Risk. Note the absence of a Level Zero - there is NEVER zero risk of avalanche; except when there is no snow at all. We use the term "skier" below to indicate anyone on the snow - skier, snowboarder, climber or walker. Avalanches don't choose.
| Avalanche Risk Level | French Flag | U.S. Color Code | Snowpack Stability | Avalanche probability | |
|---|---|---|---|---|---|
| 1 | Low Risk |  |
 |
Generally well bonded and stable. | Triggering is possible by groups of skiers on a few very steep extreme slopes. Small natural avalanches (sluffs) are possible. |
| 2 | Moderate | |
 |
Less well bonded on some steep slopes, otherwise generally well bonded. | Triggering is possible by groups of skiers, particularly on steep slopes. Large natural avalanches may occur but are not likely. |
| 3 | Considerable |  |
 |
Moderately to weakly bonded on many steep slopes. | Triggering is possible, even by individual skiers. The bulletin may indicate many slopes which are particularly affected. Medium and occasionally large natural avalanches may occur. |
| 4 | High | |
 |
Weakly bonded in most places. | Triggering is likely, even with single skiers, on many steep slopes. Frequent medium or large sized avalanches are likely. |
| 5 | Very High (Extreme) |
 |
 |
Weakly bonded and largely unstable. | Numerous large natural avalanches are likely, even on moderately steep terrain. |
The What, Where and What to do
The following are taken from the U.S. Avalanche Danger Descriptors and give a useful summary of each level - and how you should adapt your off-piste route planning accordingly.
| Danger Level | Avalanche Probability and Avalanche Trigger | Degree and Distribution of Avalanche Danger | Recommended Action in the back country | |
|---|---|---|---|---|
| WHAT | WHY | WHERE | WHAT TO DO | |
| 1 | Low Risk | Natural avalanches very unlikely. Skier-triggered avalanches unlikely. | Generally stable snow. Isolated areas of instability. | Travel is generally safe. Normal caution advised. |
| 2 | Moderate | Natural avalanches unlikely. Skier-triggered avalanches possible. | Unstable slabs possible on steep terrain. | Use caution in steeper terrain on certain aspects (defined in accompanying statement). |
| 3 | Considerable | Natural avalanches possible. Skier-triggered avalanches probable. | Unstable slabs probable on steep terrain. | Be increasingly cautious in steeper terrain. |
| 4 | High | Natural and human triggered avalanches likely. | Unstable slabs likely on a variety of aspects and slope angles. | Travel in avalanche terrain is not recommended. Safest travel on windward ridges of lower angle slopes without steeper terrain above. |
| 5 | Very High (Extreme) |
Widespread natural or human triggered avalanches certain. | Extremely unstable slabs certain on most aspects and slope angles. Large destructive avalanches possible. | Travel in avalanche terrain should be avoided and travel confined to low angle terrain well away from avalanche path run-outs. |