Appenzeller Alpen

After this week's snowfall, the snow depths in the north and west are well above average for the time of year. The fresh and drifted snow has been deposited on a sometimes unfavourable old snow surface. In addition, deeper in the snowpackSnow deposited on the ground in a multiplicity of layers.EAWS glossary there are faceted weak layersSnowpack layer in which the crystals are poorly bonded and the layer has the potential to fail. Typical crystals in dry weak layers causing avalanches are : precipitation particles; surface hoar; faceted crystals; hollow crystals; graupel. Generally >1mm in size, loose grains with few bonds Wet weak layers can be formed by all snow crystal/grain types.EAWS glossary that are prone to triggering, especially on shady slopes above approximately 2400 m and generally in the high Alpine regionsAreas above approximately 3000 m (particularly glaciated areas).EAWS glossary. In the regions exposed to heavier precipitation in the west, these layers have in some cases been thickly overlaid and in these places the snowpack is becoming increasingly stabilized. In regions which have seen less fresh snowfall, avalanches in these weak layers can still be triggered by human activity.

With northerly winds, Wednesday saw the formation of snowdrift accumulations which are prone to triggering, especially on the Main Alpine Ridge and in the south.

In the north, conditions were very cloudy with showers. The snowfall level was between 500 and 700 m, there were clear intervals in the inneralpine regions and the southern flanks of the Alps were sunny with northerly winds.

Fresh snow

From Tuesday evening to Wednesday afternoon, above approximately 1000 m:

• northern flank of the Alps, northern Lower Valais: 20 to 40 cm
• eastern Jura, rest of Lower Valais, northern and central Grisons: 10 to 20 cm
• elsewhere a few centimetres, dry in the south.

In total, the following amounts of fresh snow fell above approximately 2000 m between Sunday evening and Tuesday afternoon:

• extreme west and northern Lower Valais: 90 to 120 cm, with up to 150 cm on the border with France
• neighbouring western Lower Valais, Vaud Alps, northern flank of the Alps from the western Bernese Alps to Titlis: 60 to 90 cm
• Jura, rest of Lower Valais, northern Upper Valais, northern flank of the Alps east of Titlis: 40 to 60 cm
• southern Upper Valais without southern Visp valleys and without southern Simplon area, and over a widespread area of Grisons: 20 to 40 cm
• southern Visp valleys, southern flank of the Alps: 5 to 20 cm

Temperature

At midday at 2000 m, between -7 °C in the north and -4 °C in the south

Wind

• On the main Alpine ridge and in the south during the night to Wednesday moderate to strong, during the day moderate northwesterly to northerly
• Otherwise light to moderate from the north

During the night to Thursday, there will be some further snow showers on the northern flank of the Alps and in Grisons down to low altitudes. Some clouds will remain in the east in the morning, otherwise it will be sunny in the mountains during the day.

Fresh snow

Northern flank of the Alps, Grisons: 1 to 10 cm

Temperature

At midday at 2000 m, around -5 °C in the north and -2 °C in the south

Wind

• On the main Alpine ridge and south of there during the night to Thursday, sometimes moderate to strong, otherwise light to moderate north-northeasterly
• Moderate Bise wind in the western Jura

On Friday conditions will be mostly sunny in the mountains. In the afternoon, cloud will gather from the north-west. The zero-degree level will rise to 2000 m, and the wind will be light to moderate from the north-east. During the night to Saturday, there will be a little precipitation in the north, falling as snow above approximately 1500 m. On Saturday there will be variable cloud, and conditions will be sunny in the south. Winds will be light to moderate west-northwesterly.

The risk of dry avalanches will continue to decrease, while the possibility of gliding avalanches will increase in the west and north on steep sunny slopes.