Snow conditions 19. 1. 2024

General avalanche danger level - Friday, 19. 1. 2024
The danger is 3rd degree on the European five-level scale - CONSIDERABLE.
Main problem: new snow, wind slab, wet snow
Danger pattern: Cooling after warm weather / warming after cold

Risk assessment
Avalanche danger is CONSIDERABLE, 3rd degree, across the country above the treeline, MODERATE, 2nd degree, below the treeline. Today's cold snow fell on a much warmer snow base, so faceting is occurring near the interface. This gradually weakens snowpack stability, and the northeast wind will deposit additional load mainly on south and southwest slopes until Saturday afternoon. In the forest, due to reduced wind speed and less snow transport, this threat is somewhat smaller. Sunday warming in the mountains will not significantly affect snowpack stability, but in the hills and lowlands the snowpack will be less stable mainly on Sunday and Monday due to daytime melt. There, wet loose snow avalanches can release especially on steep grassy slopes.

Snow conditions
In the second half of the night, light rain began, above 1500 m light snow. In the early morning hours, cold air started flowing from the east near the ground, and as it advanced toward the sea, precipitation intensified and the snow line quickly lowered. By mid-morning, snow was falling everywhere except in the Primorska lowlands. 20-40 cm of snow accumulated, even more in places in the Posavje, Škofjeloško and Cerkljansko hills. In most of the country, snow fell on warm bare ground. Almost all fresh snow is dry, as cooling was rapid. Most snow fell with moderate northerly wind, only in the high mountains of the Western Karawanks and Julian Alps it initially snowed with weak southwesterly wind. Already during snowfall, new wind slabs formed above the forest. On the most wind-exposed sites, the snow cover is scoured to the hard, icy base. Already during snowfall, faceting began near the interface between previous and today's snow due to temperature difference. Faceted layers markedly worsen snowpack stability by reducing inter-layer cohesion.

Forecast weather development
Overnight clearing everywhere, clear until Sunday afternoon when high clouds arrive from the northwest. Bora on Primorska will ease somewhat by morning, but Saturday morning NE wind in mountains will strengthen, gusting over 60 km/h. Wind calms Sunday night, little wind in mountains on Sunday. Warming - from Saturday morning to Monday morning by more than 10 °C. Sunday afternoon zero isotherm near 2000 m, Monday strengthened southwest wind lifts it to 3000 m.

Snow conditions tendency
Saturday sunny but cold and windy. Strengthened northeast wind will mainly above the forest continue transporting snow and building slabs especially on south and southwest slopes. At the same time, faceting continues in the snowpack; reduced layer cohesion from faceting and additional loading from wind slab will likely cause spontaneous slab avalanches in high mountains especially near ridges. Faceting this time also occurs in forest shelter, so avalanches can be triggered even in very steep forest. Saturday snow above 1000 m likely remains dry, Sunday midday sun will already wet it on pronounced sun-exposed slopes and overnight to Monday melt-freeze crust will form there. Monday daytime melt starts even earlier. Lower down snow wets already Saturday, Sunday and Monday daytime melt may trigger some wet loose snow avalanche.

Next issue: Monday, 22. 1. 2024

Source: ARSO