Persistent weak layers
- All elevations
Considerable danger of dry and wet avalanches will be encountered in some regions.
The avalanche prone locations for dry avalanches are to be found in particular on steep north and east facing slopes above approximately 2400 m. Single snow sport participants can release avalanches. Avalanches can be released in the weakly bonded old snow and reach large size in isolated cases. Such avalanche prone locations are barely recognisable, even to the trained eye. The avalanche prone locations for wet avalanches are to be found in particular on steep east and west facing slopes below approximately 2600 m. Already in the early morning medium-sized to large wet avalanches are possible. Backcountry touring calls for experience in the assessment of avalanche danger and careful route selection.
Snowpack On north-facing slopes above approximately 2200 m more than anywhere else, there are expansively metamorphosed (faceted) weak layers deeply embedded inside the snowpack over widespread areas. In the Valais and on the northern flank of the Alps these weak layers are for the most part blanketed over by thick layers of fresher snow. Avalanches in those places can be triggered in these expansively metamorphosed (faceted) layers only in some places, in particular where the snow on the ground is relatively shallow. Particularly in Grisons, such avalanche triggerings are still relatively easy in some places. The places where avalanches can be triggered by persons are incrementally decreasing in frequency, nevertheless large-sized avalanche triggerings are still possible. South-facing slopes are thoroughly wet extending up to over 3000 m. Also on west-facing slopes the snowpack has become thoroughly wet up to nearly 3000 m. On east-facing slopes the process of the snowpack becoming thoroughly wet up to 2400 to 2800 m is proceeding apace, on north-facing slopes to between 1500 and 1800 m. Wet-snow avalanches can trigger naturally in the weak layers of the old snowpack or also be triggered by persons. As a consequence of rainfall, wet-snow avalanches can also be expected on north-facing slopes. Observed weather review Thursday, 23.03.2023 Nocturnal skies were partly cloudy and in the Valais there was a small amount of precipitation. During the daytime hours it was partly sunny in the southern regions and in Grisons, in other regions of Switzerland skies were heavily overcast. Fresh snow In the Valais at high altitudes, only a few centimetres of fresh snow was registered. Temperature At midday at 2000 m, +6 °C. Wind Winds were blowing predominantly at light to moderate strength from southwesterly directions. Weather forecast through Friday, 24.03.2023 On Thursday night, precipitation is expected to set in from the west. During the daytime hours on Friday, precipitation is anticipated over widespread areas. The snowfall level will decend from 2400 m down to nearly 2000 m during the course of the day. Fresh snow Between Thursday evening and Friday afternoon, the following amounts of snowfall are anticipated above 2600 m:
Temperature Temperatures are expected to drop. At midday at 2000 m, approximately +3 °C. Wind Winds in the northern regions and in general at elevated altitudes will be blowing at strong velocity, in some places at storm strength, from southwesterly directions. Outlook through Sunday, 26.03.2023 On both days, precipitation is anticipated over far-reaching areas. The snowfall level will descend on Friday night from 2000 m down to approximately 1200 to 1400 m. Between Saturday afternoon and Saturday night, a brief interim in precipiation is anticipated. All in all, on both days the following amounts of precipitation are anticipated: in the furthermost western part of Lower Valais: 40 to 60 cm of fresh snow; in the other regions of Switzerland 15 to 30 cm; in the southern and the inneralpine regions of Grisons, less. In the south it is expected to be partly sunny on Saturday. The winds will frequently be blowing at strong velocity from westerly directions. The danger of dry-snow avlanches is expected to increase significantly in the major areas of precipitation. The danger of wet-snow avalanches will incrementally decrease as temperatures drop.
Bulletin data: WSL Institute for Snow and Avalanche Research SLF (CC BY 4.0)