Churfirsten and Rhine Valley
Appenzeller Alpen
Stable day. Low, with only wind slab named — visible where it sits, and easy to go round.
Day Risk Profile
Avalanche Problems
Wind slab
1
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
The Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary contains coarse-grained 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 in many places. North of a line from the Rhône to the Rhine, these layers are thickly covered and triggering by human activity is no longer very likely. The main danger here stems from the fresh and drifted snow which, on northern slopes, has in places been deposited on 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. South of a line from the Rhône to the Rhine, breaks in the deeper weak layers are again expected with the sometimes large amounts of fresh snow over the weekend, and, as a result, avalanches in these areas may sometimes become very large.
Weather review for Friday
In the south there was broken cloud, but elsewhere conditions were sunny.
Fresh snow
-
Temperature
At midday at 2000 m, between +3 °C in the north and 0 °C in the south
Wind
Moderate southwesterly
Weather forecast to Saturday
Conditions will be very cloudy. There will be widespread precipitation, which will be heavy in the south during the day. The snowfall level will start at 1500 m and drop to 700 m in the north and 1300 m in the south.
Fresh snow
Until Saturday afternoon above approximately 1600 m:
- main Alpine ridge from the Monte Rosa area to the San Bernardino Pass and south of there: 30 to 50 cm, in western Ticino up to 60 cm
- western and central parts of the northern flank of the Alps, northern Valais, main Alpine ridge in Lower Valais, Val Bregaglia: 15 to 30 cm
- elsewhere less, largely dry in northern Grisons and Lower Engadine
Temperature
At midday at 2000 m, between -7 °C in the northwest and -2 °C in the southeast.
Wind
- Strong southerly during the night, foehn wind in the valleys of the north
- The sometimes strong southerly wind will continue during the day in the south and generally in the Areas above approximately 3000 m (particularly glaciated areas).EAWS glossary, while in the north at intermediate altitudes the wind will be a light to moderate northwesterly
Outlook
Sunday
Precipitation will continue to fall during the night and will be very heavy in the south. A little precipitation will continue during the day especially in the south, but elsewhere it will become increasingly sunny. From Saturday afternoon a further 40 to 70 cm of snow will fall on the main Alpine ridge from the Monte Rosa area to the San Bernardino Pass, and a widespread 20 to 40 cm elsewhere. The snowfall level will be at low altitudes in the north and at 1300 m in the south. There will be a moderate and locally strong easterly wind overnight, veering south at higher altitudes during the day.
Avalanche danger will increase significantly overnight in all regions.
In the regions exposed to heavier precipitation and in the southern parts of Grisons, breaks in the 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 deep in the Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary are expected with the increasing quantities of fresh snow. It is expected that danger level 4 (high) will be reached on the main Alpine ridge from Upper Valais to the San Bernardino Pass and south of there. Naturally triggered avalanches are expected, which may become very large especially in the case of north-facing starting zones. Exposed transportation routes will be increasingly at risk.
On the main Alpine ridge in Lower Valais, in the southern parts of central Grisons and in the Upper Engadine, many sometimes large naturally triggered avalanches are also expected due to the weak Snow deposited on the ground in a multiplicity of layers.EAWS glossary structure. Danger level 4 (high) may also be reached here, although it is mainly Alpine snow sports terrain that is at risk.
Monday
Conditions will be sunny in the south. Elsewhere it will be cloudy with bright intervals, with a little snow falling above approximately 1100 m in the afternoon. A moderate to strong westerly wind will rise in the north over the course of the day.
The danger of dry avalanches will decrease, but conditions will remain precarious for winter sports participants away from the pistes. Where there is sunshine, the fresh snow will also make moist avalanches likely.