The “Comparative snow depth” map is published from 1 November to 30 June at around 7:00 a.m. It shows the current snow depth in comparison with the long-term mean (1991–2020) for the corresponding calendar day.
The relative snow depth maps are based on snow modelling by the SLF’s operational snow-hydrological service (OSHD). In this case, a simplified model variant is used, which is suitable for climatological applications and long time series. Snow depths from this model are calculated daily on a 1 km grid. Model input consists of temperature and precipitation grids based on measurement data from MeteoSwiss, as well as measured snow depths from 350 stations. The model provides both the reference dataset for the long-term means and the current assessment.
Because the temperature and precipitation grids are only available in the afternoon, the snow depth for the current day is first estimated in the morning based on the current ICON forecast and then updated at around 1:45 p.m. once the MeteoSwiss grid data become available.
Relative snow depths are not displayed where the long-term mean of the reference period is below 10 cm.