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
In the north-west and north, last week's thick layers of fresh and drifted snow are settling and consolidating. Thin layers of fresh and drifted snow from Thursday are lying on these, and the underlying Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary has 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 places in the middle part of the Snow deposited on the ground in a multiplicity of layers.EAWS glossary. Avalanches triggered in near-surface layers can sometimes propagate into these deeper layers of old snow and occasionally become very large. This is particularly the case in the extreme west of Lower Valais and on the northern Alpine ridge.
The past week's layers of fresh and drifted snow are thinner in Ticino, Grisons and some regions in southern Valais than they are further north. They are lying on 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. People can still very easily trigger avalanches in the old snowpack in these regions, even over relatively large distances.
Weather review for Thursday
During the night to Thursday, a short break in precipitation was followed by fresh precipitation from the south-west. The snowfall level was between 800 m on the southern flank of the Alps and 1400 m on the western part of the northern flank of the Alps.
Fresh snow
From Wednesday afternoon to Thursday afternoon, above approximately 1600 m:
- Vaud and Fribourg Alps, northern and extreme west of Lower Valais, central and southern Ticino, Upper Engadine and neighbouring central Grisons, Val Poschiavo: 15 to 30 cm
- otherwise mostly 5 to 15 cm
Temperature
At midday at 2000 m, around -4 °C
Wind
- Overnight to Thursday moderate to strong from southerly directions
- During the day initially light to moderate, then moderate to strong from westerly directions
Weather forecast to Friday
North of the Main Alpine Ridge, conditions will be very cloudy with persistent snowfall at times. There will be less snowfall and brighter periods in the inneralpine regions. Conditions will be mostly sunny south of the Main Alpine Ridge.
Fresh snow
The snowfall level will be around 1000 m. The following amounts of snow will fall from Thursday afternoon to Friday afternoon:
- western Lower Valais, northern flank of the Alps, northern Grisons: 15 to 30 cm, with up to 40 cm in some places in the extreme west of Lower Valais and along the northern Alpine ridge
- western Jura, other parts of Lower Valais, northern Upper Valais, central Grisons: 5 to 15 cm
- elsewhere less; mostly dry on the southern flank of the Alps
Temperature
At midday at 2000 m, between -4 °C in the north and +1 °C in the south
Wind
Northwesterly:
- strong, storm-force at times on the northern and main Alpine ridges
- elsewhere mostly moderate at high altitudes
Moderate to strong northerly on the southern flank of the Alps, down into the valleys
Outlook to Sunday
Saturday
In the north, conditions will be mostly very cloudy with precipitation especially on the central and eastern parts of the northern flank of the Alps until midday. The snowfall level will rise from 1000 to 1400 m, in the west to 1600 m. In Valais, conditions will become increasingly sunny over the second half of the day, with brighter spells on the western part of the northern flank of the Alps. The southern flank of the Alps will be mostly sunny. The mountains will see a moderate to strong, occasionally storm-force northwesterly wind.
Avalanche danger will decrease slowly. In western and northern regions with a lot of snow, people may trigger avalanches, especially in the near-surface layers of the Snow deposited on the ground in a multiplicity of layers.EAWS glossary. In southern Valais, northern Ticino and Grisons, avalanche danger will decrease only very slowly due to the thinner snow cover on the very weak Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary. In these regions, conditions for touring and off-piste skiing will remain critical in many places.
Sunday
Conditions will be mostly sunny with extensive broken cloud, especially on the northern flank of the Alps, in northern Grisons and in the Lower Engadine. The westerly wind will ease significantly, and temperatures will become markedly warmer.
Avalanche danger will decrease. Especially in southern Valais, northern Ticino and Grisons, but conditions for touring and off-piste skiing will remain critical in many places.