Middle Lys Valley

The wind slabs must be evaluated with care and prudence in all aspects above the tree line.

The wind slabs must be evaluated with care and prudence in all aspects above the tree line.

As a consequence of a strong wind from westerly directions, further wind slabs formed in the last few days in gullies and bowls and behind abrupt changes in the terrain. These are easy to recognise but in some cases prone to triggering. They can be released easily in some places in all aspects above the tree line. Mostly avalanches are medium-sized. The areas where the wind was most intense and long-lasting were those in the western and southern sectors, on the border with France and Piedmont respectively. On steep, little used shady slopes the avalanches can penetrate even deep layers and reach large size in isolated cases. Wind-loaded slopes where weaknesses exist in the old snowpack are especially unfavourable. Whumpfing sounds and the formation of shooting cracks when stepping on the snowpack are a clear indication of a weakly bonded snowpack.

The wind slabs of the last few days are lying on unfavourable layers in particular on steep shady slopes above approximately 2300 m. Above the tree line snow depths vary greatly, depending on the infuence of the wind. All types of snow are found on the surface: loose snow in shaded and sheltered areas, wind-compacted snow with increasingly harder accumulations as you climb higher, sastrugi, eroded areas, and melt-and-freeze crusts on sunny slopes and at lower altitudes. In steep terrain there is a danger of falling on the hard snow surface.

As a consequence of low temperatures the snowpack can not consolidate during the next few days. The wind slabs remain in some cases prone to triggering.