Churfirsten and Rhine Valley
Appenzeller Alpen
Manageable day. Moderate, with wind slab at the surface — the evidence is there to read before you commit to a slope.
Day Risk Profile
Avalanche Problems
Wind slab
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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
In the north, the storm-force northerly winds are transporting the large volumes of fresh snow and, towards the south in particular, also the Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary. This is resulting in all regions in snowdrift accumulations that are prone to triggering; in the north these accumulations are becoming large. Fresh and drifted snow is being deposited on variable surfaces: on north-facing slopes, especially in sheltered locations, onto very loose snow, whereas up to high altitudes on south-facing slopes often onto a Layer of hard-compacted snow resulting from a melt-freeze process or wind.EAWS glossary. In many cases, the surface of the old snowpack has also been profiled by the wind and is irregular.
In the inneralpine regions of Valais and Grisons in particular, 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 remain in near-ground layers of the Snow deposited on the ground in a multiplicity of layers.EAWS glossary. In addition, near-surface layers in locations sheltered from the wind contain snow-covered 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, in which avalanches have repeatedly been triggered over the last week Avalanches are likely to triggered with increasing frequency in the Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary in these regions.
Weather review for Wednesday
After a mainly clear night, the morning was mostly sunny. From midday, heavy cloud gathered from the northwest, with precipitation setting in in the afternoon. The snowfall level dropped from 1500 m to around 1000 m.
Fresh snow
A few centimetres on the northern flank of the Alps
Temperature
At midday at 2000 m, around 0 °C in the northwest, elsewhere around +3 °C
Wind
- Moderate southwesterly during the night
- Increasingly strong, locally storm-force westerly during the day in the west and north
Weather forecast to Thursday
There will be widespread snowfall down to low altitudes, and this will be heavy in the night in the north. The south will be mostly dry with sunny intervals.
Fresh snow
From Wednesday afternoon to Thursday afternoon, above 1000 m:
- northern Alpine ridge: 40 to 60 cm, from the Grimsel Pass to the Glarus Alps up to 70 cm
- rest of the northern flank of the Alps, rest of Lower Valais, rest of the Gotthard region, rest of northern Grisons and Lower Engadine north of the Inn: 20 to 40 cm
- Jura, rest of Valais, rest of central Grisons, Upper Engadine north of the Inn: 10 to 20 cm
- elsewhere less, mostly dry in the south
Temperature
Cold, at midday at 2000 m between -10 °C in the north and -6 °C in the south
Wind
Storm-force northwesterly to northerly
Outlook
Friday
Overnight to Friday snow will continue to fall in the north down to low altitudes. A further 15 to 30 cm of snow is expected on the northern Alpine ridge, elsewhere less. Precipitation will come to an end in the morning and conditions will become increasingly sunny from the west. The south will be dry and mostly sunny. During the night the wind will be a strong to storm-force northerly, veering northeasterly and easing somewhat over the course of the day.
Overnight the danger of dry avalanches will continue to increase somewhat in the north, but will not change significantly during the day and in the south. With solar radiation, moist snow slides from the fresh snow are to be expected in the afternoon.
Saturday
The night to Saturday will be mostly clear. The day will start mostly sunny, but cloud will move in from the northwest in the afternoon. The wind will be a light to moderate northeasterly. Temperatures will become somewhat milder, with the zero degree level rising in the north to around 1200m and in the south to around 2000 m.
The danger of dry avalanches will decrease in all regions. With solar radiation, moist snow slides from the fresh snow are to be expected.