In alpine environments, snow cover is the predominant seasonal effect. Snow cover normally develops from a series of winter storms and is modified by the action of rain, wind and melting. Thus, to show seasonal effects not present in the original orthoimagery, we need to simulate effects such as snow accumulation, snow ablation and melt. In mountainous areas, the amount of snow present at any given location is highly variable. This is particularly noticeable in late spring and early summer, as southern and western aspects melt out exposing the underlying ground, while north facing slopes are still covered in deep snow.