Persistent weak layers
- All elevations
At elevated altitudes a considerable avalanche danger will be encountered in some regions.
In some places avalanches can be released in deep layers and reach dangerously large size. These avalanche prone locations are to be found in particular in areas where the snow cover is rather shallow. Fresh and somewhat older wind slabs are in some cases prone to triggering. These avalanche prone locations are to be found in gullies and bowls, and behind abrupt changes in the terrain and adjacent to ridgelines. The number and size of avalanche prone locations will increase with altitude. Backcountry touring calls for careful route selection.
Individual gliding avalanches and moist snow slides are possible. This applies below approximately 2200 m.
Snowpack The mostly strong westerly wind will transport fresh and loosely bonded old snow on north facing slopes. On north facing slopes in particular, where the snow drift accumulations form on a loosely bonded snow surface, they will be prone to triggering. In particular on west, north and east facing slopes above approximately 2200 m, weak layers exist relatively deep in the snowpack. On east and west facing slopes, during the mild periods in March these layers became partly or thoroughly moist up to high altitudes. During the colder period at the start of April, they froze at least to some extent and have therefore become more stable. In particular in Grisons and southern Valais, avalanches can still be triggered in deeper weak layers of the snowpack, as repeatedly demonstrated by a small number of avalanches. This applies in particular in areas where the snow cover is shallow and above approximately 2600 m. In addition, a weak layer still exists in the near-surface layers of the snowpack in some places. In Lower Valais and on the northern Alpine ridge, the snow depths are slightly below average to average. In the other regions they are well below average for the time of year, including in the high Alpine regions. Observed weather review Tuesday, 11.04.2023 It was mostly overcast. Above 1500 to 1800 m snow fell at times, in particular in the north. Fresh snow From Monday evening until Tuesday afternoon above approximately 2000 m:
Temperature At midday at 2000 m: between -1 °C in the north and +2 °C in the south Wind From the west to southwest
Weather forecast through Wednesday, 12.04.2023 After overcast skies with a little precipitation on Tuesday night, in the morning the foehn will give rise to bright spells in the north; it will be quite sunny in Valais and overcast in the south. In the afternoon precipitation will return to all regions. Fresh snow The snowfall level will be approximately 1800 m in the west and south, and approximately 1500 m in the east. From Tuesday evening until Wednesday afternoon the following amounts of snow will fall:
Temperature At midday at 2000 m: between +4 °C in the north and 0 °C in the south Wind From the west to southwest
Outlook through Friday, 14.04.2023 Thursday The north will be very cloudy with further, mostly showery precipitation. The snowfall level will be below 1000 m. 15 to 30 cm of snow will fall in the west, and 20 to 40 cm will fall in the east. In the central part of the southern flank of the Alps it will be fairly sunny. At elevated altitudes there will be a moderate and sometimes strong northwesterly wind. The avalanche danger will increase in the north over a wide area. Friday The precipitation will die away as the day progresses. It will be partly sunny for a while. In the afternoon it will become duller again from the west. The cold weather will persist for the time being, and at elevated altitudes the northerly wind will be moderate to strong at times. The avalanche danger will not change significantly.
Bulletin data: WSL Institute for Snow and Avalanche Research SLF (CC BY 4.0)