Snow conditions 19. 12. 2024

General danger level - Thursday, 19. 12. 2024
Danger is level 1 on the European five-point scale - LOW.
Main problem: favourable conditions, wind-blown snow
Danger pattern: Cold weather, poorly bonded fresh snow with wind
Danger pattern: Cooling after warm weather / warming after frost

Risk assessment
By Monday, two weather disturbances will pass us, which, except in the high mountains of the Western and Southern Julian Alps, will not bring much new snow. Avalanche threats will nevertheless appear mainly due to significant cooling and strong northerly winds. New snow deposits will form mainly on sun-exposed slopes where old frozen base is already present - there the probability of slab avalanches will increase. Therefore, the general avalanche danger level will be MODERATE, level 2, from Friday to Monday.

Snow conditions
Due to significant warming at altitude, a strong temperature reversal has occurred, with temperatures above freezing up to the highest peaks. The air in the mountains is very dry and warm, so the snow transforms distinctly differently on sun-exposed and shaded slopes. The existing snow softens and melts on sun-exposed slopes during the day, slightly refreezing at night. In shaded locations, it is mostly dry or frozen. There is little snow, mostly drifted into deposits. Especially in shaded locations, but everywhere in the morning hours, the base can be icy.

Forecast weather development
On the coastal side of the Dinaric-Alpine barrier, mid-mountain below 1500 m is already covered in low cloud, higher up and elsewhere in the mountains it is still mostly clear. Around midday, cloudiness will spread eastward, with light precipitation already appearing in the west. Snow will fall above 1800 m. With the strengthening southwesterly wind in the late afternoon, light precipitation will spread towards central Slovenia. In the middle of the night to Friday, with the arrival of the cold front from the north, precipitation will intensify and spread across the country. The snow line will drop below 1000 m, especially lower in the south. The most snow will fall in the Western and Southern Julian Alps, up to 50 cm of new snow above 1800 m, and up to 30 cm lower. Elsewhere, less precipitation, up to 30 cm of snow. On Friday morning, precipitation will ease, first in the north. It will remain cloudy, with strong northerly winds blowing, exceeding 100 km/h in exposed locations by evening. In the evening, it will clear from the northwest. Saturday will be sunny with some high cloudiness mainly in the morning. The northerly wind will ease somewhat by morning. It will be colder, with the zero isotherm around 1000 m. The night from Saturday to Sunday will be clear. On Sunday morning, the southwesterly will strengthen, cloudiness will gradually increase from the west during the day, temporarily somewhat warmer. In the evening, light precipitation will appear in the west, snow above 800 m. Precipitation will intensify slightly in the night to Monday and spread eastward. The snow line will likely drop to the lowlands, but precipitation will be light - a few cm of snow possible below 800 m. More precipitation on the Dinaric barrier and in the Western and Southern Julian Alps, up to 20 cm of new snow above 800 m. Moderate southwesterly during precipitation, strengthened northerly on Monday morning. Colder again.

Trend in snow conditions
New dry snow will fall on the old warm snowpack, which strong northerly winds will then abundantly redistribute during significant cooling. Wind-blown snow areas will form in leeward locations, mainly on the southern side of ridges. On sun-exposed slopes in the high mountains, old icy base is already present, to which new or wind-blown snow will not bond well. Especially there, the probability of slab avalanches, triggerable even with minor load, will increase. Wind-exposed spots will remain scoured, sometimes to the old icy base, requiring appropriate winter equipment for safe travel.

Next issue: Monday, 23. 12. 2024

Source: ARSO