Wind slab
- Above 2,600 m
Snowpack
With increasing westerly winds and the onset of snowfall, small snowdrift accumulations formed on Tuesday in the west and north at altitude. With snowfall intensifying and the strong to stormy westerly wind, these will continue to grow overnight to Wednesday and become large.
Before the current snowfall, an extensive, cohesive snowpack was present, mainly on north-facing slopes above 2800 m and generally in high Alpine regions. Lower and medium elevations were snow-free. At high altitudes, there was little snow in particular on shady slopes, with terrain roughness often not yet leveled out. The snow surface is angular in places on shady slopes, making it an unfavourable base for the sometimes abundant amounts of fresh snow and the fresh snowdrift accumulations.
Weather forecast to Wednesday, 20.11.2024
During the night to Wednesday, there will be intense precipitation in the west and north, which will lessen slightly during the course of the day. Over the course of the night, the snow line will drop from 1800 m to 1000 m, and then to lower levels during the day. South of the main Alpine ridge, it will be mainly sunny with a northerly wind.
Fresh snow
From Tuesday evening to Wednesday afternoon, the following amounts of fresh snow are expected above approximately 2200 m:
- western Lower Valais, northern Alpine ridge from Les Diablerets to the Glarus Alps: 50 to 70 cm, and up to 80 cm on the border with France;
- remaining north slope of the Alps and Lower Valais: 30 to 50 cm;
- southern Upper Valais, remaining Gotthard area: 15 to 30 cm;
- otherwise 5 to 15 cm, largely dry in Sottoceneri
Temperature
Temperatures will fall, reaching between -8 °C in the north and -4 °C in the south at midday at 2000 m.
Wind
- Strong to stormy from the west during the night to Wednesday
- During the day in the north, strong northwesterly to northerly and dying down to a degree, in the south moderate to strong north wind
Weather review for Tuesday, 19.11.2024
In the west and north, it was cloudy and precipitation began on Tuesday morning. The snow line was at 1500 m and rose to 1800 m over the course of the day. It was partly sunny in the south.
Fresh snow
The following amounts of fresh snow were recorded above approximately 2200 m:
- westernmost and northern Lower Valais: 10 to 15 cm, in the far west 20 cm
- elsewhere: a few centimetres, or dry
Temperature
At midday at 2000 m, around 0 °C.
Wind
Westerly to southwesterly:
- moderate to strong in the west and north
- otherwise, light to moderate.
TrendThursday
Widespread heavy cloud, with some snow falling even in low-lying areas. In the afternoon, the precipitation will intensify and the snow line will briefly rise to around 2000 m. In the west and north, an estimated 15 to 30 cm of snow is expected to fall at altitude, with up to 40 cm in the far west. In the afternoon, a strong to stormy southwesterly wind is expected.
The risk of spontaneous dry avalanches will initially decrease but may increase again in the afternoon at altitude. Individuals will still be able to trigger avalanches, even major ones. In addition, rain will mean wet slides and gliding snow avalanches are possible in the afternoon at low and medium altitudes.
Friday
The precipitation will initially still be intense during the night to Friday, and the snow line will once again reach low-lying areas. Snowfall will ease in the morning. In the Lower Valais, on the northern slopes of the Alps, another 20 to 50 cm of snow is possible, with less elsewhere. The forecast is still uncertain. There will be a strong westerly to northwesterly wind.
The avalanche risk may rise again to level 4 (major) in the main precipitation areas at altitude, but otherwise it will not change significantly.
Bulletin data: WSL Institute for Snow and Avalanche Research SLF (CC BY 4.0)