The following signs of instability indicate an elevated risk of triggering avalanches:
- Recent avalanche activity, particularly slab avalanches that have occurred in the last 48 hours.
- Remote-triggered avalanches. This is where an avalanche occurs on a slope some distance from where it was triggered. Often, remote-triggered avalanches are triggered from flatter terrain adjacent to avalanche slopes, such as ridge crests, benches or areas immediately below avalanche paths.
- Whumpfs are the collapsing of a weak layer in the snowpack. It often has an accompanying loud 'whumpf' sound.
- Shooting cracks that appear in the snow from under your sled, skis, board, snowshoes or feet.
- Hollow or drum-like sounds caused by moving over the snow surface.
- Snow shedding naturally from trees, which suggests the snowpack is warming rapidly.
- Snow pinwheeling or snowballing down slopes, which are other signs of a warming snowpack.
These signs of instability indicate the snowpack structure is primed for human-triggering. The weight of a person or machine moving over the snow could be sufficient to release an avalanche. If you notice any of these signs, the safest course of action is to avoid exposure to avalanche terrain. Stick to low angled, simple terrain, or routes that stay within densely forested terrain.
The absence of signs of instability does not indicate the absence of avalanche danger.