Snow conditions 20. 12. 2024

General danger level - Friday, 20. 12. 2024
The danger is 3rd degree on the European five-level scale - CONSIDERABLE.
Main problem: new snow, windslab
Danger pattern: Cold weather, poorly bonded fresh snow with wind
Danger pattern: Cooling after warm weather / warming after frost

Risk assessment
Up to Thursday morning, up to 40 cm of new snow fell in the mountains in the last 24 hours, in the area of southern and western Julian Alps possibly a little more, around 70 cm. In the area of southern and western Julian Alps above 1800 m the avalanche danger level is CONSIDERABLE, 3rd degree, elsewhere MODERATE, 2nd degree. The main dangers are new snow and windslab. With north wind, new snow drifts are forming mainly on sun-exposed slopes, where old frozen base layer is already present. There the probability of slab avalanche release is increased. Conditions in high mountains are demanding.

Snow conditions
During the last snowfall the snow line was initially high, between 1600 m and 1800 m. With the passage of the cold front the air cooled rapidly. New dry snow fell on older snowpack, which was scarce and icy in places. Strong wind builds drifts mainly on south sides of slopes and ridges. During recent snowfalls graupel may have formed in places between precipitation layers, acting as a potential weak layer.

Expected weather development
Today, Friday, initially cloudy and foggy, light snow still falling. By midday precipitation will stop, from north clearing will start in the evening. Strong, gusty north wind on exposed sites. Temperature at 1500 m around -4, at 2500 m around -9 °C. Saturday mostly clear. Mostly light north winds. Temperature at 1500 m around -3, at 2500 m around -8 °C. Sunday west and southwest wind will blow, cloudiness increasing during the day. Light snow will appear in the evening, slightly strengthening overnight to Monday, mainly in the south of the country. Amount of new snow in mountains presumably small. During precipitation moderate southwesterly, Monday morning strengthened northerly. Cooler again.

Trend of snow conditions
New dry snow fell on old snow cover, which was then abundantly redistributed by strong north wind during pronounced cooling. In lee positions, mainly on south side of ridges, areas of windslab are forming. On sun-exposed slopes in high mountains old icy base is already present, with which new or windslab snow will not bond well. Especially there the probability of slab avalanche release will increase, which can be triggered also by smaller load. Wind-exposed places will remain scoured, in places even to old icy base, which requires use of appropriate winter equipment for safe travel.

Next issue: Monday, 23. 12. 2024

Source: ARSO