Waadtländer Voralpen

Wind slabs and weakly bonded old snow require caution.

As a consequence of a strong northwesterly wind, wind slabs will form during the night. The fresh and older wind slabs are to be evaluated with care and prudence in steep terrain. They are mostly small but in some cases prone to triggering. Avalanches can additionally in isolated cases be released in deeper layers also. These can in some cases reach medium size. Such avalanche prone locations are to be found in particular at transitions from a shallow to a deep snowpack. Apart from the danger of being buried, restraint should be exercised in particular in view of the danger of avalanches sweeping people along and giving rise to falls.

Snowpack From southern Valais through the Gotthard region to Grisons, numerous soft faceted layers exist in the snowpack between compacted layers and crusts. These faceted layers are especially prevalent in places with shallow snow cover, where the snowpack can be penetrated down to the ground by skis. On the northern flank of the Alps the base of the snowpack is well bonded in many instances, but multiple faceted layers exist nearer the surface. The bonding of the snowpack is most favourable in the extreme west of Lower Valais and in northern Lower Valais. On wind-protected slopes in all regions, the near-surface layers of the snowpack are increasingly faceted and loosely packed. A layer of surface hoar has formed on the snowpack in some places. A strong to storm force northwesterly wind and some fresh snow in the central and western parts of the northern flank of the Alps will give rise to extensive snow drift accumulations on Monday night. The drifting snow will be deposited on the old snow surface, which is faceted in many places, and therefore be prone to triggering. Where the wind has exerted an influence adjacent to ridgelines and in pass areas, the fresh snow drift accumulations are less prone to triggering. Observed weather review Monday, 30.01.2023 After a clear night, it was quite sunny at first before becoming increasingly cloudy from the northwest in the afternoon. Fresh snow - Temperature At midday at 2000 m: about -5 °C in the north and 0 °C in the south Wind From the northwest

• Moderate to strong during the day, but strong to storm force on the main Alpine ridge and generally at elevated altitudes
• In the south in the afternoon, north foehn

Weather forecast through Tuesday, 31.01.2023 In the north, light snowfall will commence on Monday evening and cease during Monday night. The north and east will be sunny for a time once the residual cloud disperses, before becoming increasingly cloudy again in the afternoon. The south will be mostly sunny. Fresh snow In the period from Monday evening until Tuesday morning, approximately 5 cm of snow, locally as much as 10 cm, will fall in the central and eastern parts of the northern flank of the Alps and in northern Grisons and northern Lower Engadine. Temperature At midday at 2000 m: about -4 °C in the north and 0 °C in the south Wind During the night

• Moderate, sometimes strong, from westerly directions
• At elevated altitudes and in the south, strong to storm force from northerly directions

During the day

• Light to moderate from westerly directions
• At elevated altitudes, moderate, on the main Alpine ridge and in the east, strong, from the northwest

Outlook through Thursday, 02.02.2023 Wednesday On Wednesday the weather will be changeable. In the northeast a little snow will fall above 600 m during the night and the daytime. As the day progresses, cloud will build up from the north; sunny weather with persist longer in the inneralpine regions and the south. At elevated altitudes there will be a moderate to strong wind, becoming sometimes storm force in the evening, from northwesterly directions. The avalanche danger will not change significantly. Thursday On Wednesday night, snowfall will arrive from the northwest. During the day, snow will fall over a wide area and in some cases persistently. The snowfall level will be approximately 700 m. By the evening, 20 to 40 cm will fall in the Bernese Oberland, in the central and eastern parts of the northern flank of the Alps and in northern Grisons. Elsewhere 5 to 15 cm of snow will fall over a wide area, but it will remain dry in the far south. A strong, sometimes storm force northwesterly wind will persist. As a consequence of fresh snow, wind and the unfavourable old snow surfaces, the avalanche danger will increase significantly in the north as the day progresses. In the south it will not change significantly.