Considerable avalanche danger will be encountered in some regions
Edition: 13.12.2021, 17:00 / Next update: 14.12.2021, 18:00
Snowpack
The weekend’s snow drift accumulations are still prone to triggering in some places.
On west, north and east facing slopes above approximately 2200 m in practically all regions, weak layers with faceted crystals exist near the base of the snowpack. In western Lower Valais and on the northern flank of the Alps the weak old snow is mostly embedded deep, so that the probability of avalanches releasing in this weak base layer is small. From central Valais through Ticino to Grisons and generally in places with shallow snow cover, the bonding of the snowpack is least favourable and the probability of avalanches releasing in the old snow is highest.
As a consequence of significant warming and radiation as the day progressed, the surface of the snowpack became moist both below approximately 1500 m and, at higher altitudes, on steep sunny slopes in particular. Mostly clear skies on Monday night will give rise to a brittle melt-freeze crust on the surface of the snowpack.
Gliding avalanche activity has increased as a consequence of the warming, and gliding avalanches are to be expected in the coming days as well. In the western and northern regions with a lot of snow, these can reach a large size in some cases.
Observed weather on Monday, 13.12.2021
Sunday night was mostly overcast in the east, and a few snowflakes fell in some localities. Otherwise the night skies were mostly clear. During the day, the weather in the mountains was mostly sunny; the east was partly sunny with cloudbanks. With the zero degree level at 3000 m in the west and south, and 2400 m in the east, it was very mild for the time of year.
Fresh snow
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Temperature
At midday at 2000 m: between +5 °C in the west and +2 °C in the east, and about +6 °C in the south
Wind
  • In the central and eastern parts of the main Alpine ridge, moderate to strong, easing in the afternoon, otherwise light to moderate, from the north to northeast
  • At elevated altitudes in the Jura, a moderate to strong bise
Weather forecast through Tuesday, 14.12.2021
Tuesday will be fairly sunny in the mountains, but occasionally relatively dense cloudbanks will pass over. It will remain mild.
Fresh snow
-
Temperature
At midday at 2000 m: between +6 °C in the west and south, and +4 °C in the east
Wind
Light to moderate, veering from northeasterly to northwesterly, becoming moderate on the main Alpine ridge as the day progresses
Outlook through Thursday, 16.12.2021
In the mountains the coming days will be mostly sunny. It will remain mild. The wind will be light to moderate from the north to northeast.
The danger of dry avalanches will decrease, but in the regions from central Valais through northern Ticino to Grisons only slowly on shady slopes. The danger of moist avalanches will increase during each of the coming days. Gliding avalanches are still to be expected. In the regions with a lot of snow, these can reach a large size.