Natural Hazards and Earth System Science www.nat-hazards-earth-syst-sci.net 1561-8633 1684-9981 2 3/4 2002 10.5194/nhess-2-247-2002 http://www.nat-hazards-earth-syst-sci.net/2/247/2002/ http://www.nat-hazards-earth-syst-sci.net/2/247/2002/nhess-2-247-2002.html http://www.nat-hazards-earth-syst-sci.net/2/247/2002/nhess-2-247-2002.pdf 247 253 0000-00-00 Nearest neighbour models for local and regional avalanche forecasting M. Gassner B. Brabec WSL, Swiss Federal Institute for Snow and Avalanche Research, SLF Flüelastr. 11, CH-7260 Davos, Switzerland This paper presents two avalanche forecasting applications NXD2000 and NXD-REG which were developed at the Swiss Federal Institute for Snow and Avalanche Re-search (SLF). Even both are based on the nearest neighbour method they are targeted to different scales. NXD2000 is used to forecast avalanches on a local scale. It is operated by avalanche forecasters responsible for snow safety at snow sport areas, villages or cross country roads. The area covered ranges from 10 km² up to 100 km² depending on the climatological homogeneity. It provides the forecaster with ten most similar days to a given situation. The observed avalanches of these days are an indication of the actual avalanche danger. NXD-REG is used operationally by the Swiss avalanche warning service for regional avalanche forecasting. The Nearest Neighbour approach is applied to the data sets of 60 observer stations. The results of each station are then compiled into a map of current and future avalanche hazard. Evaluation of the model by cross-validation has shown that the model can reproduce the official SLF avalanche forecasts in about 52% of the days.