These factors include terrain, weather and the local snowpack conditions. The most likely terrain for avalanche occurrence is generally on open slopes with an angle between about 30 and 45 degrees. Under very unstable snow conditions avalanches can also occur on lower angled slopes. Statistically, the greatest number of avalanche fatalities has occurred on slopes of about 38 degrees. Another key terrain factor to consider includes the aspect of a particular slope relative to any recent strong winds.
Windward slopes tend to either be wind hardened or scoured of new snow by winds.
Another terrain factor includes the shape of the slope that may strongly influence the distribution of stresses within the snowpack. This is especially true when significant snowfall is accompanied by rapid rises in temperature or when snow changes to rain. Strong winds that often accompany snowfall may deposit heavy amounts of snow and build potential slab layers on lee slopes. Winds may also help build large cornices along ridges. These cornices can become unstable to the added weight of a single skier, snowboarder or snowmobile and may release naturally when warming occurs, causing avalanches on slopes below.