Location and extent of avalanche starting zones are of crucial importance to correctly estimate the potential danger that avalanches pose to roads, railways or other infrastructure. Presently, release area assessment is based on terrain analysis combined with expert judgment. Tools for the automatic definition of release areas are scarce and exclusively based on parameters derived from summer topography, such as slope and curvature. This leads to several limitations concerning the performance of such algorithms. Foremost, they neglect the smoothing effect of the snow cover on terrain morphology. Winter terrain often considerably deviates from its underlying summer terrain, thus changing potential release area size and location of surface slab avalanches. Hence, we present a new GIS based tool which estimates potential release areas by association of traditional contributory variables, such as slope and forest cover with variables particularly related to snow cover influence on topography. We introduce a scale dependent roughness parameter and a wind shelter parameter accounting for varying winter topography and snow deposition patterns with increasing snow depth. Further, uncertainty in the definition of the parameters is accounted for by using a fuzzy logic classification approach. This approach is especially useful for defining release area scenarios e.g. depending on snow depth, which is not possible with existing tools.