A computer-based system simulating snowpack structures as a tool for regional avalanche forecasting

This paper describes the current state of a complete automatic system of th ree numerical models that simulate snow-cover stratigraphy and avalanche ri sks for operational avalanche forecasting. The first model, SAFRAN, estimat es relevant meteorological parameters affecting snowpack evolution. The sec ond, Crocus, is a snow numerical model which simulates the physical process es inside the snowpack and its stratigraphy; The last model, MEPRA, is an e xpert system; based on an assessment of snowpack stability, it deduces natu ral and accidental avalanche risks. To describe the great variability of th e snowpack and the associated avalanche risks, this automatic system simula tes snow-cover evolution and its stability for many typical slopes, elevati ons and aspects representative of the different French massifs. To achieve this result, different kinds of validations have been carried out since win ter 1981; they are mainly based on comparisons with different sets of measu rements and on the opinion of users. Although the routinely obtained results do not yet take into account all sm all-scale effects such as wind transport, they have been considered as valu able information by avalanche forecasters since 1992-93 and used operationa lly since then.