Stoos

There is less snow than is usual at this time of year in most regions. Only in northern Lower Valais are snow depths about average. On southern slopes and generally below 2400 m, the snowpackSnow deposited on the ground in a multiplicity of layers.EAWS glossary is mostly wet or has frozen solid.

At high altitudes on the Main Alpine Ridge and to the south of there, last week’s fresh snow is 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.

Particularly in the inneralpine regions of Valais and throughout Grisons, there are sometimes pronounced 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 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 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, especially on northern and eastern slopes above approximately 2400 m. However, hardly any avalanches have been triggered in these layers for some days.

Further north, the structure of the snowpackSnow deposited on the ground in a multiplicity of layers.EAWS glossary is more favourable.

Conditions were cloudy in the south and there was some light snowfall. In the north, the dense patches of high-altitude cloud meant that there were only occasional sunny intervals.

Fresh snow

A few centimetres fell locally along the Main Alpine Ridge in Valais.

Temperature

At midday at 2000 m, between +3°C in the north and 0°C in the south

Wind

Southerly:

• strong to stormy during the night on the northern Alpine ridge, elsewhere moderate to strong
• moderate to strong during the day on the northern Alpine ridge, elsewhere often light to moderate

Cloudy in the south, elsewhere very sunny despite patches of high-altitude cloud. A little snow will fall on the Main Alpine Ridge in Valais above around 1500 m.

Fresh snow

Along the Main Alpine Ridge in Valais: up to 10 cm

Temperature

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

Wind

• Southerly, occasionally still moderate during the night, but mainly light during the day

On Wednesday afternoon, a little snow will fall in the south down to low altitudes. Elsewhere, conditions will often be cloudy with only Valais being really sunny. On Thursday, some snow will again fall in the south down to low altitudes. Along the Main Alpine Ridge in Upper Valais, 10 to 20 cm of fresh snow may fall, elsewhere less. Conditions will otherwise be sunny with a strong southerly wind.

There will be no significant change in avalanche risk on Wednesday while on Thursday it will increase where there is fresh snow, especially on the Main Alpine Ridge in Upper Valais.