Jaun

There is appreciably less snow than usual at this time of year in most regions and snow conditions for ski touring are very poor in many places. Only in northern Lower Valais are snow depths approaching average. On southern slopes and in general below 2400 m, the snowpackSnow deposited on the ground in a multiplicity of layers.EAWS glossary has mostly frozen solid. On wind-protected northern slopes above approximately 2400 m, the surface of the snowpack is widely faceted.

On the Main Alpine Ridge in Valais and in western Ticino, the small volumes of fresh snow which have fallen in the last few days are lying on a thin but weak old snowpackSnow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary of faceted crystalsSnow grains, solid, with multiple flat glassy faces and sharp edges. Developed from faceting metamorphism, usually poorly bonded to one another (fewer contact points), a critical factor in avalanches if a faceted layer is covered with bonded snow. Typical grain size: 0.5 to 3 mm See also: www.snowcrystals.itEAWS glossary. With the expected arrival of fresh snow, the avalanche danger will increase rapidly in these regions. In the inneralpine regions of Valais, on the southern flank of the Alps and throughout Grisons, there are 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 of faceted crystals or surface hoarTransparent, frequently flat crystals forming on the snowpack when moist air settles on the surface. It forms most often during cold, clear, humid nights. Once it is blanketed by fresh fallen snow, surface hoar is one of the most critical weak layer. See also: www.snowcrystals.itEAWS glossary in the snowpackSnow deposited on the ground in a multiplicity of layers.EAWS glossary on shady slopes above approximately 2400 m. Although these weak layers could be triggered in stability tests, it was very rare for avalanches to be triggered. Further north, the structure of the snowpack is more favourable.

In the north, it was overcast with high stratus cloud up to around 2500 m with light snowfall down to low altitudes. Above that, it was sunny. In the south, it was still quite sunny in the morning, then increasingly cloudy, and snow began to fall in the afternoon.

Fresh snow

A few centimetres locally

Temperature

At midday at 2000 m, around -8 °C in the north, -3 °C in the south and -1 °C in the west

Wind

• Strong Bise wind in the Jura and the northern Prealps
• Otherwise mostly light easterly winds

In the south, it will be very cloudy, and snow will fall down to low altitudes. In the north, it will be sunny in the mountains.

Fresh snow

The following amounts of snow will fall above 1000 m by Thursday afternoon:

• Monte Rosa, upper Saas Valley, Simplon region, Binntal: 20 to 40 cm
• Rest of the Main Alpine Ridge directly along the border with Italy, Bedretto and Valle Maggia: 10 to 20 cm
• Northern neighbouring regions, Aletsch region, rest of Ticino, Moesano, Val Bregaglia and Bernina region: 5 to 10 cm

Temperature

At midday at 2000 m, between 0 °C in the north and -4 °C in the south

Wind

• Southeasterly winds, strong during the night, stormy in the high alpine regionsAreas above approximately 3000 m (particularly glaciated areas).EAWS glossary
• Easing significantly during the day

On Friday morning, the snowfall will end in the south and it will then be widely sunny in the mountains. It will become increasingly mild.

The avalanche danger will decrease only slowly in areas with new fallen snow, otherwise it will remain largely unchanged.