Snowpack stability is a local property of the snowpack describing the propensity of a snow-covered slope to avalanche (Reuter and Schweizer, 2018). Snowpack stability is described using four classes: very poor, poor, fair, and good.
1. Depending on the avalanche type, snowpack stability is described by:
- Failure initiation, crack propagation and slab tensile support (slab avalanche) (Reuter and Schweizer, 2018)
- Loss of strength/bonding (loose-snow avalanche) (e.g., McClung and Schaerer, 2006)
- Loss of basal friction and slab tensile and/or compressive support (glide-snow avalanche) (e.g., Bartelt et al., 2012).
2. Snowpack stability is inversely related to the probability of avalanche release. Snowpack stability describes the snowpack to fail given a specific trigger (Statham et al., 2018), as for instance a person skiing a slope. Table 1 shows the relation between snowpack stability and how easy it is to trigger an avalanche.
3. The term local refers to a point which ranges in size from a potential trigger location or stability test to a starting zone.
4. All snowpack stability assessments may refer to either future (forecast) or present (nowcast) based on observations or models. E.g., if the snowpack in a release area is considered fair today, and until tomorrow a layer of new snow is expected, the stability of tomorrows snowpack including the new snow layer needs to be assessed. Likely, it has changed to poor or even very poor by that time.