Slopes in the lee of a ridge or of another wind obstacle accumulate more snow and are more likely to include pockets of deep snow, wind slabs, and cornices, all of which, when disturbed, may result in avalanche formation. Conversely, the snowpack on a windward slope is often much shallower than on a lee slope. Avalanches and avalanche paths share common elements: a start zone where the avalanche originates, a track along which the avalanche flows, and a runout zone where the avalanche comes to rest. The debris deposit is the accumulated mass of the avalanched snow once it has come to rest in the run-out zone. For the image at left, many small avalanches form in this avalanche path every year, but most of these avalanches do not run the full vertical or horizontal length of the path. The frequency with which avalanches form in a given area is known as the return period. The start zone of an avalanche must be steep enough to allow snow to accelerate once set in motion, additionally convex slopes are less stable than concave slopes, because of the disparity between the tensile strength of snow layers and their compressive strength. The composition and structure of the ground surface beneath the snowpack influences the stability of the snowpack, either being a source of strength or weakness. Avalanches are unlikely to form in very thick forests, but boulders and sparsely distributed vegetation can create weak areas deep within the snowpack through the formation of strong temperature gradients.
He was carried nearly 2,000 feet to the base of the mountain and was not successfully rescued. Classification
European avalanche risk
In Europe, the avalanche risk is widely rated on the following scale, which was adopted in April 1993 to replace the earlier non-standard national schemes. Descriptions were last updated in May 2003 to enhance uniformity.In France, most avalanche deaths occur at risk levels 3 and 4. In Switzerland most occur at levels 2 and 3. It is thought that this may be due to national differences of interpretation when assessing the risks. [1] Stability:

Generally described in more detail in the avalanche bulletin (regarding the altitude, aspect, type of terrain etc. )[2] additional load:

heavy: two or more skiers or boarders without spacing between them, a single hiker or climber, a grooming machine, avalanche blasting
light: a single skier or snowboarder smoothly linking turns and without falling, a group of skiers or snowboarders with a minimum 10 m gap between each person, a single person on snowshoesGradient:

gentle slopes: with an incline below about 30°
steep slopes: with an incline over 30°
very steep slopes: with an incline over 35°
extremely steep slopes: extreme in terms of the incline (over 40°), the terrain profile, proximity of the ridge, smoothness of underlying ground

European avalanche size table
Avalanche size:

North American Avalanche Danger Scale
In the United States and Canada, the following avalanche danger scale is used. Descriptors vary depending on country.