In mountain snow basins, a change in climate will likely cause a change in the basin snow cover extent. A procedure for evaluating whether a given climate change scenario will speed up or slow down the seasonal decrease of snow covered area is outlined with hypothetical examples for a simple basin. This procedure has two main purposes. First, it can be used to generate snow covered area data in a new climate for input to runoff models such as the Snowmelt-Runoff Model (SRM). Second, it could potentially be used to provide input to climate models that require knowledge of the land area covered by snow at a given time. A computer program is now operational for use on real basins and is demonstrated on the Rio Grande basin in Colorado and the Illecillewaet River basin in British Columbia.