Nock Mountains

Combined wet and persistent weak layer problem

Combined wet and persistent weak layer problem

The avalanche risk is moderate. In a few places, spontaneous wet snow avalanches and those triggered by people can occur in all aspects, which usually remain medium-sized but can occasionally accumulate large amounts of wet snow. In addition, medium to large dry slab avalanches can be triggered by individuals in a few places, especially on shady slopes above the tree line. Danger areas are difficult to recognise away from obvious pillows of wind drifted snow, which is why a defensive choice of route is still advised. This applies in particular to the tree line. Loose snow slides can easily tear through the persistent weak layer and reach dangerous sizes. There is little sliding snow activity.

The snow surface is often soft and moist on the sunny slope. The upper part of the snowpack then consists of several slab-thick layers of felt and wind slab of varying hardness, which in turn rests on an unfavourable base of faceted crystals and deep rime. Fractures primarily occur between the last packets of drift snow, but can also break through to the old snow foundation, which is usually completely transformed.

The night will start clear at first, but clouds will increase from the west. There may be light showers in the second half of the night, snow from around 1800 metres. It will remain dry in Lungau. On Sunday, the sky will often be overcast and short showers may fall, from about 1700 m as snow. In Lungau it will remain dry and some sunshine is possible. The wind will remain weak. Around 0 degrees at 2000 metres.

The persistent weak layer problem continues to make the situation tense and difficult to calculate in the terrain. Outgoing longwave radiation on Monday night is severely limited.