Middle Lys Valley

Wind slabs represent the main danger. There is a danger of falling on the hard snow surface.

Wind slabs represent the main danger. There is a danger of falling on the hard snow surface.

As a consequence of a strong wind from westerly directions, clearly visible wind slabs formed in gullies and bowls and behind abrupt changes in the terrain. They can be released, especially by large additional loads, in all aspects above the tree line. 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. Wind-loaded slopes where weaknesses exist in the old snowpack are especially unfavourable. On steep, little used shady slopes the avalanches can be triggered in deep layers of the snowpack. Mostly avalanches are medium-sized.

The wind slabs of last week 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. In addition, only a small amount of snow is lying for the time of year in all altitude zones. 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. It is recommended to have crampons or ranpant.

The more recent wind slabs remain in some cases prone to triggering. As a consequence of new snow and strong wind there will be a gradual increase in the avalanche danger.