Aigle-Leysin

As a consequence of new snow and a strong to storm force southerly wind, avalanche prone wind slabs formed. Avalanches can in some places be released by people and reach medium size. Fresh wind slabs are to be evaluated with care and prudence. Backcountry touring calls for careful route selection.

As a result of fresh fallen snow and winds, wide-ranging snowdrift accumulations are being generated at high altitudes in southern regions. These accumulations are prone to triggering in some places. The fresh snow is being deposited atop bare ground at high altitudes on south-facing slopes. On north-facing slopes the snow level prior to the snowfall lay at 2000 m. Previous to the current round of snowfall the snowpack evidenced pronounced effects of sunshine over widespread areas. Thus, the bonding to the layers of fresh fallen snow and freshly generated snowdrifts was relatively favourable. Only on north-facing slopes in the high alpine regions was the snowpack surface still loosely-packed in some places. There, the bonding of fresh snow to the old snowpack can be inadequate in some places. South-facing slopes are thoroughly wet far up into high alpine regions; west-facing and east-facing slopes are wet below approximately 3000 m; north-facing slopes below approximately 2400 m. In the major areas of precipitation it is possible that avalanches can fracture down into the entire thoroughly wet snowpack and sweep it along.

Nighttime skies on Friday were still somewhat clear to start with, subsequently they became heavily overcast. In the southern regions, precipitation set in. During the daytime on Saturday in the northeastern regions there were bright intervals, in the other regions of Switzerland skies remained predominantly overcast and in the southern regions there was further precipiation registered. The snowfall level lay at 2000 m Fresh snow: Between Friday evening and Saturday afternoon the following amounts of fresh snow were registered above approximately 2200 m:

• Temperature: At midday at 2000 m, +5 °C in the northern regions and 0° C in the southern regions. Wind:

Monday: In the western and the northern regions, snowfall is expected above approximately 1600 m. In the Lower Valais and on the northern flank of the Alps, approximately 15 to 30 cm of fresh snow is expected. In the southern regions the precipitation will slacken off and it will become partly sunny. The danger of dry-snow avalanches is expected to increase in the northern regions. In the southern regions the danger of dry-snow avalanches will decrease, there are nearly no further naturally triggered avalanches to be expected. As a consequence of solar radiation in the southern regions, however, moist-snow slides can be expected to release from the fresh fallen snow. Tuesday: In the western regions it will be rather sunny, in the southern regions partly sunny. In the northeastern regions skies will still be overcast, however only a small amount of snowfall is anticipated. At high altitudes more than anywhere else, strong-velocity westerly winds can generate fresh snowdrift accumulations. In the major areas of precipitation in the south, the danger of dry-snow avalanches is expected to diminish. As a consequence of solar radiation and daytime warming, wet-snow avalanches releasing from the fresh snow can be expected in the Valais and on the southern flank of the Alps more than anywhere else.