Avalanches may release spontaneously on a few steep slopes. Avalanches can get large enough to bury a large truck or destroy several houses (size 4).
Avalanches may release spontaneously on some steep slopes. Avalanches can get large enough to bury a car or destroy a small house (size 3).
Avalanches may release spontaneously on some steep slopes. Avalanches can get large enough to bury or even kill you (size 2).