Waadtländer Voralpen

Moderate avalanche danger will be encountered over a wide area. Wind slabs and weakly bonded old snow require caution

Moderate avalanche danger will be encountered over a wide area. Wind slabs and weakly bonded old snow require caution

Fresh and somewhat older wind slabs are small but prone to triggering. As a consequence of new snow and strong wind they will increase in size appreciably in the afternoon. The wind slabs are to be evaluated with care and prudence in steep terrain. Avalanches can additionally in very isolated cases be released in deep layers, mostly by large additional loads. They can reach medium size. These avalanche prone locations are barely recognisable, even to the trained eye. Caution is to be exercised on little-used, rather lightly snow-covered shady slopes. On steep grassy slopes mostly small gliding avalanches are possible in particular at intermediate altitudes.

In the lower part of the snowpack, particularly on west-facing, north-facing and east-facing slopes above approximately 2200 to 2400 m, as well as on south-facing slopes above approximately 2800 m, there are weak layers evident. These can be triggered by persons in some places, more than anywhere else in central Valais over the Ticino as far as Grisons. In the furthermost western part of Lower Valais and on the northern flank of the Alps these weak layers are covered over by thick layers of fresher snow so that they can hardly be triggered by persons. On west-facing, north-facing and east-facing slopes more than anywhere else, the fresh fallen snow and freshly generated snowdrifts are being deposited on top of a weak old snowpack surface composed of expansively metamorphosed (faceted) snow crystals or surface hoar. On south-facing slopes the snowpack surface manifests pronounced effects from the sun, at intermediate altitudes also from rainfall in some places, which makes it more favourable. As a consequence of higher temperatures, increasingly frequent small-sized gliding avalanches have released at intermediate altitudes during the last few days.

On the Main Alpine Ridge and southwards therefrom it was sunny in some areas, in the other regions of Switzerland skies were overcast accompanied by a small amount of precipitation. The snowfall level in the furthermost northern regions lay at approximately 1600 m to start with, elsewhere at approximately 1200 m. Fresh snow: - northern flank of the Alps, northern Valais and the highest summits of the eastern part of the Jura region: 5 to 10 cm; in the other regions of Switzerland, less; - in the eastern part of the Jura region, approximately 20 mm of rainfall was registered during Saturday night. Temperature: At midday at 2000 m, -1 °C. Wind: Winds were westerly, blowing at light to moderate strength. During the night in northern regions, a few centimetres of snow will fall above approximately 1300 m. Subsequently skies will clear. In the early morning hours in the furthermost eastern regions there will be sunny intervals, elsewhere skies will be overcast everywhere, and during the afternoon precipitation is expected to set in from the west. In the furthermost western regions the snowfall level will ascend to approximately 1600 m. Fresh snow: Between Sunday afternoon and Monday afternoon, the following amounts of fresh snow are anticipated: - northern Alpine Ridge west of the Aare, furthermost western part of the Lower Valais, Jura region: 5 to 10 cm; - in the other regions of Switzerland, approximately 5 cm; in Grisons and the southern regions, less. Temperature: At midday at 2000 m, +1 °C in the northern regions and -4 °C in the southern regions. Wind: Winds will be westerly, blowing at moderate strength, at higher velocity in the western regions.

Tuesday: On Tuesday, skies will be heavily overcast. On the northern flank of the Alps, in the Valais and in the Jura region, 10 to 20 cm of fresh snow is anticipated; as much as 40 cm in the furthermost western part of Lower Valais along the French border. In Grisons there will be less precipitation. In the furthermost southern regions it will be dry and quite sunny. The snowfall level in the western regions will temporarily ascend to approximately 2000 m during the morning hours. In the other regions of Switzerland the snowfall level will lie at approximately 1500 m. The westerly winds will intensify: during the course of the day blowing at strong to storm strength in the northern regions and at high altitudes in general. The fresh fallen snow and to some extent also the loose old snow will be intensively transported. The danger of dry-snow avalanches is expected to increase over widespread areas, with the exception of the furthermost southern regions. In the western and the northern regions, Danger Level 3 (“considerable”) will be reached. In addition, as a consequence of the rainfall in western regions, wet-snow avalanches can be expected. Wednesday: On Wednesday in the northern regions and the Valais, heavy precipitation is expected. The snowfall level in the western regions will ascend from 1500 m to approximately 2800 m, in the eastern regions to approximately 2400 m. In the high alpine regions of the Valais and the northern regions, approximately 40 to 80 cm of fresh snow is anticipated, less in the southern regions and in Grisons. In the furthermost southern regions it will remain dry and predominantly sunny. Winds will be westerly to northwesterly, during the day blowing at strong velocity in the northern regions, elsewhere in Switzerland blowing at storm strength, and will intensively transport the fresh snow. Presumably, Danger Level 4 (“high”) will be reached in the Valais and in the northern regions over widespread areas. As a result of intensive, persistent rainfall, frequent and numerous wet-snow avalanches are anticipated. In addition, at high altitudes frequent large-sized dry-snow avalanches must also be expected. In Grisons and in the southern regions, avalanche danger levels are also expected to increase, but not as much.