Valais Chablais
Vouvry
Avalanche Problems
New snow + Persistent weak layers
3=
Field notes
New snow
Easy to spot - the snow is fresh. Look at recent avalanche activity in similar terrain, and pay attention to how much new snow has fallen in the last three days. Critical loading depends on temperature, wind, and what was on the surface before the storm. SLF advises waiting until the Snow deposited on the ground in a multiplicity of layers.EAWS glossary has had time to bond before committing to steep terrain in fresh snow.
Persistent weak layers
Persistent Snowpack 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 are very challenging to recognise. Distinctive noise (resembling a “whumpf” sound) occurring when a weak layer beneath a slab collapses. The air of the weak layer is forced outside the snowpack, with the resulting whumpf sound being heard. The sound usually indicates an unstable situation and can be accompanied by surface cracking. A whumpf is a clear avalanche alert.EAWS glossary sounds and shooting cracks are typical when present, but you can have a serious weak layer with no warning signs at the surface. Knowledge of how the Snow deposited on the ground in a multiplicity of layers.EAWS glossary has evolved is essential. SLF's travel advice is direct: travel conservatively, avoid terrain where the consequences of being caught are large, and treat the history of weather and snow as more important than what you can see today. Read the full bulletin.
Wet snow + Gliding snow
3=
Field notes
Wet snow
Rolling snowballs, deep penetration when you step or ski, and small natural slides are clear signals that the Snow deposited on the ground in a multiplicity of layers.EAWS glossary is losing strength. After a clear, cold night the surface often freezes into a strong supporting Layer of hard-compacted snow resulting from a melt-freeze process or wind.EAWS glossary, and conditions are favourable in the early morning. After a warm, overcast night, the problem may be present from the start of the day. Plan early returns and watch the runout zones below you.
Gliding snow
Almost impossible to predict precisely, even when the warning signs are visible. A crack visible on the snowpack surface formed by snow-gliding on steep, and particularly grass-covered slopes. Areas below slopes with visible glide cracks should be avoided whenever possible due to threat of gliding sluffs or avalanches.EAWS glossary — gaps that open in the Snow deposited on the ground in a multiplicity of layers.EAWS glossary down to the ground — are often precursors to release, but they don't tell you when. A glide avalanche can release minutes after the cracks appear, or weeks later, or not at all. Some release without any visible warning. Avoid lingering anywhere near glide cracks: above them, alongside them, or below in the runout.
Snowpack & Weather
Snowpack
The fresh snow and wind slabs are lying on soft layers, especially on slopes that are protected from the wind, and in some places Transparent, 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 has also covered by snow. Overnight to Monday, the wind slabs will continue to grow in size, especially on the central and eastern parts of the northern flank of the Alps. In addition, the rain has caused the Snow deposited on the ground in a multiplicity of layers.EAWS glossary to become wet and also weakened it up to 2400 m. With the partly cloudy night and the sun on Monday, more wet and gliding avalanches are to be expected.
On shady slopes above approximately 2400 m and in the Areas above approximately 3000 m (particularly glaciated areas).EAWS glossary in general, there are faceted Snowpack 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 deep in the Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary. With the new and drifted snow, fractures are again possible in isolated cases. Avalanches may then become large.
Weather review for Sunday
It was very cloudy with light precipitation at first, which became heavier in the afternoon from the west. The snowfall level was around 1500 m and rose to 2200 m in the west.
Fresh snow
From Saturday night to Sunday afternoon, the following amounts fell above approximately 2400 m in the west and 1800 m in the east:
- Northern flank of the Alps west of the Reuss, Valais: 20 to 30 cm.
- Northern flank of the Alps east of the Reuss, rest of the Gotthard region: 10 to 20 cm
- Grisons, Ticino not including the Gotthard region: less than 10 cm, dry in the very south
Temperature
At midday at 2000 m, around +1 °C
Wind
Southwesterly:
- Strong in the north and at high altitudes in general, storm force at times in the west
- Light to moderate in Grisons
Weather forecast to Monday
Intense precipitation will fall in the north on Sunday evening. The snowfall level will rise to around 2200 m. In the west, the precipitation will end during the night and it will be mostly sunny during the day. The last precipitation will fall in the late morning in the east, then it will remain partly cloudy. It will be dry and fairly sunny in the south.
Fresh snow
From Sunday afternoon to Monday morning, the following amounts are expected to fall above approximately 2400 m:
- Northern flank of the Alps east of the Kandertal, as well as Prättigau, Silvretta, Samnaun: 20 to 30 cm.
- Rest of northern flank of the Alps, rest of northern Grisons: 10 to 20 cm
- Elsewhere less than 10 cm across a wide area, dry in the very south
Temperature
At midday at 2000 m, around +4 °C
Wind
From the west:
- Strong during the night in the north and generally at high altitudes, storm force at times
- Mostly moderate during the day, easing off as the day progresses
Outlook
Tuesday and Wednesday will be fairly sunny and mild. The zero-degree level will be around 3400 m. There will be a light to moderate southwesterly wind.
The risk of dry avalanches will decrease. Gliding avalanches are still possible on steep grassy slopes. In addition, moist snow slides are also possible during the day at high altitudes on steep sunny slopes.