What Do Field Observations Tell Us About Avalanche Danger? (original) (raw)

The avalanche forecast regions in Canada range from 100 to 30,000 km 2 , far larger than the 10 km 2 covered in a typical backcountry day. This difference in scale could cause the danger a recreationist is exposed to, the local avalanche danger, to differ from the regional bulletin. This study examines the relationship between field observations (instability, snowpack, and weather factors), which do not require digging a snow profile, and the local avalanche danger. The results were grouped for analysis by the dominant avalanche character of the day: Loose Dry, Wet (loose and slab), Wind Slab, Storm Slab, Persistent Slab, and Deep Slab. Throughout the past 6 winters we have created a unique dataset of 28 field observations from 425 field days. Univariate and multivariate cross-validated classification trees were built to examine the predictive capability of the observations for the local danger. Storm, Persistent, and Wind Slab avalanche characters had the most field observations correlate significantly with the local danger, and Wet (loose and slab) had the least. Observations of Slab Avalanche Activity, New Snowfall, and Tree Bombing were applicable for the most avalanche characters. Univariate and multivariate classification trees can be useful to recreationists in interpreting critical observations and the combinations of these observations that indicate elevated danger.