Vaud Alps
Bex-Villars
Day Risk Profile
Avalanche Problems
New snow + Persistent weak layers
4=
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
2
Field notes
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.
Snowpack & Weather
Snowpack
There is appreciably less snow in all regions than is usual for the time of year, especially at low and intermediate altitudes. The large amounts of fresh snow expected in the west and north over the next few days will fall on a Snow deposited on the ground in a multiplicity of layers.EAWS glossary that is unfavourable in many areas, the surface of the snowpack being faceted and loose in many places. In addition, there are distinct 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 that are prone to triggering in the middle and lower parts of the snowpack, especially on western, northern and eastern slopes, particularly south of a line from the Rhone to the Rhine. North of this, the snowpack structure is somewhat more favourable, but even in these regions there are weak layers deeper in the Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary. Against this background, a rapid and significant increase in avalanche danger is in prospect, especially in the west and north.
Weather review for Tuesday
Conditions were overcast on Tuesday, with light precipitation in almost all regions and with snowfall levels of between 1000 and 1500 m.
Fresh snow
The following amounts fell up to Tuesday afternoon:
- Jura, extreme west of Lower Valais, northern Lower Valais, Ticino: 5 to 15 cm
- elsewhere less or dry
Temperature
At midday at 2000 m, between -2°C in the north and -4°C in the south
Wind
Rising west to southwesterly, which, in the afternoon, was:
- moderate to strong in the Jura and on the northern flank of the Alps
- elsewhere light to moderate
Weather forecast to Wednesday
In the north, conditions will be very cloudy with precipitation. This will be heaviest in northern and the extreme west of Lower Valais and in the Vaud Alps. The snowfall level will rise in the west overnight to Wednesday to 2000 m and then drop to 1300 m. In Valais, it will be lower at times. In the south, conditions will be very cloudy overnight to Wednesday with some precipitation, while daytime conditions will be quite sunny.
Fresh snow
Above 2200 m:
- northern and extreme west of Lower Valais, Vaud Alps: 50 to 80 cm
- remaining western and central parts of the northern flank of the Alps, rest of Valais: 30 to 50 cm
- eastern part of the northern flank of the Alps, southern Simplon region, northern Ticino, Surselva and Prättigau: 15 to 30 cm
- rest of Ticino and rest of Grisons: 5 to 15 cm
Temperature
At midday at 2000 m, between -2 °C in the north and 0 °C in the south
Wind
- Along the Prealps, strong to storm-force westerly to southwesterly in the west and north at high altitudes
- In Ticino and Grisons mostly moderate, initially from the southwest, then from the northwest
Outlook for Thursday and Friday
Thursday
In the north, conditions will continue to be very cloudy with persistent, heavy precipitation at times. The westerly wind will remain strong to storm-force, especially on the northern flank of the Alps and in the west. The amount of fresh snow is expected to be similar to that of the day before. The snowfall level will be between 1100 and 1300 m.
Avalanche danger will increase further generally, within level 4 in regions exposed to the most precipitation. An increased number of very large avalanches is expected in these regions, these being capable of descending right down into the valleys in the regular avalanche tracks and of endangering exposed transportation routes.
Friday
During the night to Friday, another 20 to 40 cm of snow will fall on the northern flank of the Alps, in Lower Valais and Prättigau, but less in the rest of Valais and Grisons. The snowfall level will be between 1000 and 1200 m. Conditions will be dry on the southern flank of the Alps. During the day, conditions will be cloudy with brighter intervals on the northern flank of the Alps and mostly sunny in Valais and the south. The westerly wind will subside significantly.
Avalanche danger will increase again somewhat overnight to Friday and may reach dangerlevel 4 even on the eastern part of the northern flank of the Alps and in northern Grisons. Very large avalanches are possible on the northern flank of the Alps, these being capable of descending right down into the valleys and endangering exposed transportation routes. In Grisons, on the other hand, the risk relates primarily to alpine snow sports terrain.