Persistent weak layers
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Considerable avalanche danger will be encountered over a wide area.
In some places avalanches can be triggered in the weakly bonded old snow and reach medium size in some cases. Fresh and somewhat older wind slabs are mostly small but prone to triggering. They are to be found in particular at elevated altitudes. Wind slabs are to be evaluated with care and prudence in steep terrain. In high Alpine regions the avalanche prone locations are more widespread and the danger is greater. Defensive route selection is recommended.
Below approximately 2200 m small and medium-sized gliding avalanches are possible.
Snowpack The huge amounts of snow which have fallen in the western and the northern regions since Thursday were deposited on top of soft layers of faceted crystals over widespread areas above approximately 2200 m. For that reason, fractures extending down to these deeply embedded layers are easily possible. In addition, the fresh fallen snow has been intensively transported by the strong to storm-strength westerly winds. Far-reaching snowdrift accumulations have been generated, including distant from ridgelines. The fresh fallen snow and freshly generated snowdrift accumulations tend to increase significantly with ascending altitude. Below 2200 m, the snow cover in the areas of precipitation is thoroughly wet from the rainfall, in the other regions of Switzerland the snowpack is moist up to approximately 2500 m due to the mild temperatures. Dry-snow avalanches which fracture and release at high altitudes can sweep away the entire thoroughly wet snowpack at altitudes below 2000 to 2500 m. The snow cover is only quite shallow, however. Observed weather review Saturday, 24.12.2022 During the nocturnal hours of Friday, intensive snowfall continued in the northern and the furthermost western regions. The snowfall level descended towards the end of this period of precipitation to nearly 1800 m in the western regions, to nearly 1500 m in the eastern regions. During the daytime hours on Saturday there was only a small amount of precipitation, but skies remained heavily overcast. In the furthermost southern regions it was predominantly sunny and dry. Fresh snow Between Friday afternoon and Saturday midday the following amounts of fresh snow were registered above approximately 2500 :
All in all since the onset of this period of precipitation on Thursday afternoon until Saturday midday, the following amounts of fresh snow have been registered above approximately 2500 m:
Temperature At midday at 2000 m, between +3 °C in the southwestern regions and 0 °C in the northeastern regions. Wind Winds in the northern regions and in general at elevated altitudes were blowing at strong velocity from the west. Weather forecast through Sunday, 25.12.2022 It will be predominantly sunny and mild. The zero-degree level is expected to ascend to 3000 m. Fresh snow - Temperature At midday at 2000 m, between +7 °C in the northern regions and +3 °C in the southern regions. Wind Winds will be blowing at moderate to strong velocity, in some high alpine regions at storm-strength, from westerly directions. Outlook through Tuesday, 27.12.2022 Monday On Boxing Day it will be quite sunny to begin with. During the course of the day, cloud cover will increase from the northwest and in northern regions precipitation will set in during the afternoon. The snowfall level will descend from approximately 2000 m down to nearly 1600 m by evening. In the southern regions it is expected to remain dry and rather sunny. At elevated altitudes, a moderate to strong-velocity westerly wind will be blowing. The avalanche danger levels are expected to decrease slightly. Nevertheless, for winter sports enthusiasts in outlying terrain away from secured ski runs, the avalanche situation remains treacherous. Tuesday During Monday night in the western regions above 2000 m, and in the eastern regions above 1600 m, a small amount of snowfall is expected. On Tuesday morning the precipitation will come to an end and it will become rather sunny. Temperatures will drop somewhat, the zero-degree level will lie at 1700 m. Avalanche danger levels are not expected to change significantly
Bulletin data: WSL Institute for Snow and Avalanche Research SLF (CC BY 4.0)