The seasonal snowpack dynamics of the Siberian mountains and plains play a critical role in the freshwater fluxes of northern rivers into the Arctic Ocean. This study is part of a larger project seeking to quantify the freshwater discharge of the Ob River (Russia) to the Arctic, using satellite remote sensing and hydrologic modeling. Subareas of the Tom River watershed (a tributary to the Ob) are delineated using digital elevation and land cover data within a Geographical Information System (GIS). Daily satellite snow images for 1981 to 1985 are analyzed with the GIS to give time series of percent snow cover for each subarea. These time series are compared with model-generated snow cover visually and statistically, allowing spatially distributed evaluation of the model's snow sub-routines. This study will contribute to improved models and better understanding of important and climate-sensitive snow processes and freshwater supply in Arctic river basins.