Considerable danger of dry and wet avalanches will be encountered in some regions
Edition: 8.5.2021, 17:00 / Next update: 9.5.2021, 18:00
Snowpack
The great amounts of fresh snow which fell in the northern and western regions on Friday have by and large stabilised. The layers of fresh snow and freshly generated snowdrifts are still prone to triggering on high-altitude, steep north-facing slopes more than anywhere else. There, as the consequence of strong-velocity southerly winds, additional snowdrift accumulations are still being generated. In the south and in Grisons the snowdrift accumulations are relatively small.
Beneath the fresh snow and snowdrifts of this week, the old snow is thoroughly wet below approximately 3000 m on east-facing, south-facing and west-facing slopes, and below 2200 to 2500 m on north-facing slopes. As a result of higher daytime temperatures, the stabilising crusts on the snowpack surface as well as inside the snow cover tend to soften up. During the course of the day, naturally triggered wet-snow avalanches can be expected. These releases can sweep along the entire snow cover with them, particularly on north-facing slopes below approximately 2500 m.
Observed weather on Saturday, 08.05.2021
Following a night of clear skies it was predominantly sunny. During the course of the day it became significantly warmer.
Fresh snow
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Temperature
At midday at 2000 m, between +5 °C in the western regions, +1 °C in the eastern regions and +3 °C in the southern regions. Temperatures tended to rise further during the afternoon.
Wind
Winds were blowing at light-to-moderate strength from southerly to southwesterly directions.
Weather forecast through Sunday, 09.05.2021
Following a night of predominantly clear skies it will be sunny to start with. During the course of the day, clouds will move in, initially in southern regions, during the afternoon also in western regions.
Fresh snow
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Temperature
At midday at 2000 m, between +12 °C in the northern regions and +8 °C in the southern regions. Zero-degree level at 3800 m.
Wind
  • Winds in early morning will still be blowing at moderate strength, intensifying to strong-to-storm strength during the course of the day, from southwesterly directions;
  • in the Alpine valleys of the north, a strong foehn wind will prevail.
Outlook through Tuesday, 11.05.2021
In the southern regions skies will be heavily overcast. On Monday, precipitation is anticipated, to start with in the Valais sector of the Main Alpine Ridge and in western Ticino. On Tuesday, snowfall is expected which will be intensive on the Main Alpine Ridge and southwards therefrom. The snowfall level on Monday will still lie at 2600 m, subsequently it will descend to 2000 m by Tuesday evening. In the northern regions, foehn-induced bright intervals are expected on Monday. On Tuesday, snowfall is expected, including in the northern regions above approximately 2000 m.
On Monday, a storm-strength southerly wind will be blowing in all regions of Switzerland. On Monday night, the wind will incrementally slacken off, to start with in the western regions, subsequently also in the eastern regions.
In the southern regions the danger of dry-snow avalanches will increase significantly at elevated altitudes. On Tuesday it is currently assumed that Danger Level 4 (High) will be reached. Above approximately 2500 m, naturally triggered dry-snow avalanches can be expected as a result of the fresh snow and strong-to-storm strength winds; and wet-snow avalanches below 2500 m, as a result of the intensive rainfall. In the northern regions, the avalanche danger levels are not expected to change significantly on Monday; on Tuesday danger levels will increase as a result of the fresh snow.