Snow avalanches are a danger that annually cause the highest average number of casualties in Slovenia. They are limited to a smaller part of the terrain in Slovenia, as they predominantly occur in high mountain regions. The factors that trigger snow avalanches are complex and often quite unpredictable. Nonetheless, it is important to understand the conditions of the snow cover that are more susceptible to triggering avalanches. Weather plays a crucial role. In the thesis, we focused on the occurrence of snow avalanches in January 2021 in Upper Posočje. Avalanches of such dimensions had not been witnessed in this region for seven decades. The studied period was characterized by above-average heavy snowfall, resulting in a record snow cover height. This was followed by strong thawing and warming with rain in the second half of January, creating suitable conditions for triggering large-scale snow avalanches. The avalanches were defined by a dense, viscous snow mass that rapidly gained both momentum and force as they moved. When comparing the snow avalanches of 2021 with those of February 1952, we can find that the weather conditions were similar and comparable. The physical geographic characteristics of the Upper Soča Valley significantly contribute to the occurrence of some of the most extensive avalanches in Slovenia. Deep valleys, substantial relief variations, and terrain jumps give the avalanche mass additional force and speed. The weather in this area, especially in the high mountain region, changes extremely rapidly. Some slopes are still bare and without vegetation due to historical extensive grazing. Understanding the conditions crucial for snow avalanche occurrence in this area could be a significant help in the future, particularly when talking about prevention.
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