Altschneeproblem

In South Tyrol, East Tyrol and Upper Carinthia, there are currently some easily triggerable weak layers in the snowpack at certain altitudes and exposures. We take a look at two current profiles from East Tyrol.

On December 15, a medium-sized slab avalanche was triggered on the Pirchkogel in the Stubai Alps. No one involved came to any harm. The skiers hit an area with a thin layer of fresh snow and were thus able to initiate the break, which ultimately spread over a large area in the weak layer.

Roughly speaking, there is now an accident-prone old snow problem in Tyrol, especially north of the Inn, as the weaker snowfall means that there is now a perfect slab above the weak layers. Further south, however, the weak layers have not disappeared, but there are far fewer places where slab avalanches can be triggered due to the thicker layers.

The influence of low pressure will remain until the weekend. It will continue to flake here and there, but the extreme snowfall - more on this in the current alert - will come to an end. This is a good thing for the core areas of the southern congestion.

The marmot greets us daily with sunshine and a mostly cloudless sky. Especially near the surface, there is a massive temperature gradient of just a few centimetres in the snow cover - often despite plus temperatures up to high altitudes.

After a brilliant start to the season in September and October, November brings us back down to earth with the autumnal high pressure - as reported by the WeatherBlog. On the sunny side, the snow cover bubbled out again right up to the top, while on the shady side, faceted weak layers formed in this constellation of settled but thin old snow cover and persistent fine weather.

Peter Höller, avalanche expert at the BFW in Innsbruck, has analyzed accident statistics from the Austrian Board of Trustees for Alpine Safety. He found that fatal avalanches in the variant area close to ski resorts are often due to new and drift snow problems, while there are proportionately more fatal accidents on classic ski tours with old snow problems.

Hazard pattern 4 - cold on warm, warm on cold - occurs when there is a large temperature difference (more than 5°C) during the snowing process or between the snow surface and the fresh snow. As the name suggests, it can occur in both temperature directions, regardless of whether it snows cold on a warm surface or vice versa.

The warm temperatures continue in February. Where it is more like spring in the valley, the touring conditions at altitude are still good, even if the snow depth in Kühtai is slightly below average for mid-February.

The Euregio Avalanche Report has brought some innovations to the world of avalanche warnings since 2018/19. These include the function of highlighting or dimming areas with a certain avalanche problem - perfect for getting a quick overview of weak layers in old snow.

Tour planning proved to be rather difficult last week, as an old snow problem in the terrain is not easily recognizable. This makes it all the more important to use your head when planning at home and choose a suitable tour carefully.

A built-up, loose snow cover from the ground to the snow surface is a product of prolonged periods of fine weather in early and mid-winter. This snow, known as nap powder, forms a weak layer that must be taken seriously as soon as it has been snowed in. This is currently the case in wind-protected and little-traveled W-N-E slopes at high altitudes.