Retrieval of wet snow extent with high temporal resolution over large areas that include topography requires use of wide swath SAR and radiometric terrain correction to enable backscatter comparisons across different orbital tracks. We report on springtime wet snow mapping using a time series of Envisat ASAR wide swath (WS) images covering the Swiss Alps. The ASAR observations were used to constrain a runoff model for a local catchment; performance was assessed with and without integration of the radar data. Our EOPI project began an unprecedentedly dense series of ASAR WS acquisitions over Switzerland in March 2012. Wet snow maps at the national scale were generated and integrated for the first time on an operational basis within the Swiss Institute for Snow and Avalanche Research SLF. Lessons learned from this initial operational integration test are discussed, with a view toward the monitoring possibilities coming soon with the Sentinel-1 radar satellites.