Snow conditions 21. 3. 2025

General avalanche danger level - Friday, 21. 3. 2025
Danger level 2 on the European 5-level scale - MODERATE.
Main problem: weak layers, wind slab
Danger pattern: cooling after warm weather / warming after cold
Danger pattern: rain

Risk assessment
Danger is MODERATE, level 2. The snowpack is least stable where there is the most wind-blown snow, e.g. near ridges. There, an avalanche can be triggered by a small load. With precipitation on Saturday, transient thaw in the night to Sunday, and continuation of precipitation on Sunday, the probability of avalanche release will gradually increase!

Snow conditions
The surface of the snowpack on sun-exposed slopes has changed in recent days in typical spring daily cycles. Especially in the afternoon, small avalanches of non-cohesive snow have spontaneously released on very steep slopes. At night, the surface froze. On shade-exposed slopes, the snow on the surface is dry; on clear nights, faceting has occurred in the top layers of the snowpack. In places on shade-exposed slopes near the top of the snowpack, there are thin denser layers (crust) formed by wind; under load, these layers break crust-like and sink into the faceted layers, which can cause loss of balance. Such collapse of the weak layer does not propagate to the surroundings and therefore usually does not lead to the release of a slab avalanche. Higher probability of release is on very steep slopes near ridges, where there is more wind-blown snow.

Forecast weather development
On Saturday it will be cloudy and foggy, light precipitation will start to appear in the Julian Alps area, which will strengthen somewhat in the afternoon and spread to most other mountains. The snow line will initially be around 1500 m, rising to around 1800 m by evening. Moderate wind will blow, possibly strong southwesterly in the high mountains. Temperature at 1500 m around 4, at 2500 m around -2 °C. On Sunday, precipitation will intensify. The snow line will be around 2000 m or higher. Moderate to strong southerly to southwesterly wind will blow. Temperature at 1500 m around 5, at 2500 m around -2 °C. On Monday cloudy, foggy in the mountains.

Trend in snow conditions
On Saturday and especially Sunday, we expect a deterioration of conditions. On Saturday in the Western and Southern Julian Alps above 1800 m up to 20 cm of snow will fall by evening, the probability of avalanche release will increase mainly near ridges, where the strengthened southwesterly will build wind slabs. Elsewhere, much less precipitation. With transient thaw in the night to Saturday, larger snow avalanches will also spontaneously release below 2000 m. By Monday, more than 50 cm of snow will fall in the high mountains of the Western Julian Alps above around 2200 m. Elsewhere in the high mountains, less new snow, expected up to 30 cm. During snowfall, dry and wet non-cohesive snow avalanches will spontaneously release, up to Monday possibly also slab avalanches. Strengthened southwesterly will blow, transporting snow and building snow slabs in the high mountains. Slab avalanche will be possible to trigger mainly on steep slopes with small load.

Next issue: Monday, 24. 3. 2025

Source: ARSO