Snow conditions 15.12.2021

General danger level - Wednesday, 15 December 2021
Danger is 3rd degree on the European five-level scale - CONSIDERABLE.
Main problem: wind slab, wet snow
Danger pattern: Cooling after warm weather / warming after frost

Risk assessment
Avalanche danger is mainly above the treeline still CONSIDERABLE, 3rd degree, lower down, even below 1000 m above sea level, MODERATE, 2nd degree. Particularly dangerous are places with wind-blown snow, mainly on south-facing slopes above the treeline. Under the top layer of snow there are also old slabs, so the danger is hard to recognise. Even with minor loading, you can trigger a slab avalanche especially at such places. Up to an altitude of around 1500 m, the temperature is above zero, so wet snow sloughing can also be expected. This applies especially to sunny grassy slopes, but individual slabs may also release. Snow avalanches from steep slopes are also expected in the pre-alpine region; in northern Primorska, Škofja Loka hills and Polhov Grad hills, and in Zasavje.

Snow conditions
With the warming, on Tuesday the temperature rose above zero even a little above 2000 m above sea level. This and the sunny weather soaked the snow cover mainly on sun-facing slopes, while in the shade the snow remained mostly dry; today, due to rising cloud cover and thus increased humidity, it has also become somewhat soaked in gullies even at altitudes where the cloud layer is. The snow cover began to settle and transform more quickly, but at the same time it temporarily became less well bonded. Today above 1500 m it has already cooled and the snow has stabilised somewhat higher up, with a crust forming. Lower down the snow is still southerly and wet and slowly melting. Wind-exposed places are scoured, sometimes to the old or bare ground, where there is a risk of slipping. There are still quite a few slabs that are potentially unstable, especially in the high mountains on south-oriented slopes.

Forecast weather development
Today in the mid-mountains it will be mostly cloudy and foggy, with the cloud top mostly between 1400 and 1900 m above sea level. In the western Julians and in the high mountains it will be mostly clear, but there will occasionally be more cumulus clouds. A weak to moderate northerly wind will blow. The zero will be at an altitude between 1300 and 1700 m. Tomorrow it will be mostly clear. A weak to moderate northerly wind will blow. The height of the zero isotherm will fluctuate during the day. It will be warmer in the morning than in the afternoon, and on Thursday night it will temporarily warm up again. On Friday it will be mostly clear. During the day it will gradually cool slightly. A moderate, strengthened in the high mountains, northerly wind will blow. Dry but somewhat colder on Saturday, on Sunday it will warm up again.

Tendency of snow conditions
Due to the changing temperature, the snow cover will settle and transform and gradually stabilise. The relatively rapid change between warmer and colder phases will have a favourable effect. The crust will strengthen. However, the snow will remain poorly transformed in shady locations, especially in the high mountains. Avalanche danger will decrease somewhat, but in sun-facing locations, with sunny weather and warming during the day, the snow may become somewhat unstable again. Particularly dangerous will be steeper north-facing slopes where the snow is wind-blown, especially in gullies, and during the day south-facing steep slopes where the base is grassy or covered with leaves. Slabs will also be more dangerous. Spontaneous sloughing is not expected in the coming days, except perhaps some slab avalanches on steep sun-facing grassy slopes. The next avalanche bulletin will be published on Friday, 17 December 2021.

Next publication: Friday, 17 December 2021

Source: ARSO