Persistent weak layers
- Toutes altitudes
Considerable avalanche danger will be encountered over a wide area. Wind slabs and weakly bonded old snow require caution.
In all aspects avalanches can be triggered in the weakly bonded old snow and reach a dangerous size. Single winter sport participants can release avalanches easily. Remotely triggered avalanches are possible in isolated cases. Whumpfing sounds can indicate the danger. In addition avalanche prone wind slabs will form in particular in gullies and bowls, and behind abrupt changes in the terrain during the night. They are to be evaluated with care and prudence in steep terrain. Backcountry touring and other off-piste activities call for experience in the assessment of avalanche danger.
Snowpack On Monday night, in particular on the northern flank of the Alps, the strong southerly wind will transport the still loosely bonded fresh snow of recent days and give rise to snow drift accumulations that are prone to triggering. Before last week’s snowfalls, the surface of the old snowpack was faceted and loosely bonded, in particular in wind-protected terrain at some distance from ridgelines. In consequence, avalanches are most likely to be triggered at the interface between the fresh and older wind slabs and the weak old snow. In particular from southern Valais through the Gotthard region to Grisons, the entire old snowpack was often faceted as well. In these regions, avalanches can also release the entire snowpack. The bonding of the snowpack is most favourable in the extreme west of Lower Valais and in northern Lower Valais, where hardly any distinct weak layers exist. Observed weather review Monday, 06.02.2023 During the first half of the night, a little snow fell down to low altitudes over a wide area. The skies then cleared. During the day it was quite sunny in the mountains despite low stratus-like cloud cover. Fresh snow From Sunday afternoon until Monday morning above approximately 1000 m:
Temperature At midday at 2000 m: between approximately -3 °C in the west and -7 °C in the east Wind
Weather forecast through Tuesday, 07.02.2023 On Monday night a little snow will fall in the south, even at low altitudes. During the day it will be mostly sunny in all regions. Fresh snow Main Alpine ridge in Valais, Gotthard region, central part of the southern flank of the Alps: up to 10 cm Temperature At midday at 2000 m: between -6 °C in the north and -8 °C in the south Wind
Outlook through Thursday, 09.02.2023 Wednesday and Thursday will be mostly sunny and cool. The wind will be sometimes moderate from easterly directions on Wednesday, otherwise it will be light. The avalanche danger will decrease slowly.
Bulletin data: WSL Institute for Snow and Avalanche Research SLF (CC BY 4.0)