Churfirsten and Rhine Valley
Appenzeller Alpen
Day Risk Profile
Avalanche Problems
Wind slab
3-
Field notes
Look for fresh snow deposits on Slope facing downwind/ wind sheltered aspect. Snow deposits can attain several times average snow depth.EAWS glossary, in Usually a steep, elongated, eroded trench; typically prone to snowdrift accumulation.EAWS glossary and Rounded or elongated concavity; typically tending to accumulate snowdrift.EAWS glossary, and behind ridgelines and abrupt changes in terrain — these are where the wind has loaded the snow into slabs that are easy to trigger. Recent avalanches, shooting cracks under your weight, and 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 are clear confirmations of the problem. The safest move is to avoid wind-loaded terrain entirely. NB wind signs alone don't always mean an avalanche problem exists, and the age of drifted snow is hard to judge.
Snowpack & Weather
Snowpack
With the fresh snow and storm force wind, extensive wind slabs form in the north and in Valais. The large amount of new and drifted snow is prone to triggering. Naturally triggered avalanches are to be expected. These can penetrate deeper layers of the Snow deposited on the ground in a multiplicity of layers.EAWS glossary and become very large, especially on the northern Alpine ridge and in Valais.
Slightly less snow falls in Ticino and Grisons. In these regions, new and drifted snow overlay an unstable Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary with pronounced 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. Naturally triggered avalanches are also to be expected here, which are likely to be mostly medium and large in size. Avalanches can very easily be triggered by human activity, even from larger distances.
Weather review for Sunday
During the night, a little snow fell in the north down to low altitudes. During the day it was quite sunny in the Alps. In the afternoon, clouds gathered from the west.
Fresh snow
From Saturday afternoon to Sunday afternoon:
- North of a line between the Rhône and the Rhine: 10 to 20 cm
- Elsewhere: a widespread 5 to 10 cm, dry in the south
Temperature
At midday at 2000 m, between -7 °C in the north and -2 °C in the south
Wind
- Moderate to strong northerly wind at high altitudes and in the south
- The wind shifted to a westerly in the afternoon and became increasingly moderate to strong in the north
Weather forecast to Monday
There will be heavy snowfall, mainly in the north and Valais. It will remain dry only in the far south. The snowfall level will rise temporarily to 1500 m in the northwest overnight to Monday and will be around 1000 m during the day. Particularly in Grisons, precipitation amounts are uncertain.
Fresh snow
From Sunday evening to Monday afternoon above approximately 1800 m and in the Jura on the highest peaks:
- Northern Alpine ridge, Valais: 50 to 70 cm, locally up to 80 cm on the northern Alpine ridge and in westernmost Lower Valais
- Western Jura, remaining northern flank of the Alps, remaining parts of northern Grisons, northern Lower Engadine: 30 to 50 cm
- Eastern Jura, northern Ticino, central Grisons, rest of Engadine, Val Müstair: 15 to 30 cm
- Elsewhere less, and mostly dry in Sotto Ceneri
Temperature
At midday at 2000 m -5 °C in the north and -3 °C in the south
Wind
There will be westerly to northwesterly winds:
- Strong to storm force in the north and in Valais
- Moderate to strong in Grisons and Ticino
Outlook to Wednesday
On Tuesday, another 30 to 50 cm of snow will fall on the northern Alpine ridge, in Lower Valais, Prättigau, Silvretta and Samnaun, with less expected elsewhere. In the far south, it will be dry and quite sunny. The snowfall level will be at low altitude. Winds will be strong to storm force from westerly to northwesterly directions.
The forecast for Wednesday is still uncertain. Some snow is expected to fall in the north and west overnight to Wednesday. During the day it will be dry and quite sunny, especially in the south. There will continue to be strong westerly winds at high altitudes.
On Tuesday, the avalanche danger will increase further but still remain within the current danger level 4 (high). Apart from the southern valleys, danger level 4 has also been reached in the rest of Grisons. Very large naturally triggered avalanches are to be expected, especially in western and northern Valais. Very large avalanches are also possible along the rest of the northern Alpine ridge and in the rest of Valais. In the affected areas of Grisons, many medium and large avalanches are to be expected due to the weak but thin Snow deposited on the ground in a multiplicity of layers.EAWS glossary. The avalanche situation is critical.
With the end of the intense precipitation on Tuesday evening, naturally triggered avalanche activity will be appreciably reduced. The avalanche danger will decrease slightly on Wednesday, but will remain high.