Central Grisons and Anterior Rhine
Domleschg - Lenzerheide
Day Risk Profile
Avalanche Problems
Persistent weak layers
2+
Field notes
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.
Snowpack & Weather
Snowpack
There are 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 in the middle and lower part of the Snow deposited on the ground in a multiplicity of layers.EAWS glossary, particularly on wind-protected shady slopes. Such places are particularly common south of a line from the Rhone to the Rhine. In these weak layers, medium-sized and, in isolated cases, large avalanches can still be triggered by people. The snowpack on northern and eastern slopes in central Valais, as well as in northern Grisons, is most prone to triggering while north of a line from the Rhone to the Rhine, the snowpack structure is somewhat more stable and there are fewer hazardous zones.
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 has formed in many places over the past few days and where it has not been blown away, it has been covered by a layer of fresh snow, especially on the southern flank of the Alps.
Weather review for Friday
Conditions on the central and eastern parts of the northern flank of the Alps were mainly sunny due to the foehn wind, but elsewhere in the north there was mainly heavy cloud cover with sunny spells. Skies were overcast on the southern flank of the Alps.
Fresh snow
-
Temperature
At midday at 2000 m, between +2°C in the north and -5°C in the south
Wind
Moderate from southerly directions, occasionally strong during the day
Weather forecast to Saturday
In the north, conditions will initially remain fairly sunny in the mountains. Clouds will thicken from the west over the course of the day. There will be heavy cloud cover on the southern flank of the Alps.
Fresh snow
There will be snowfall down to low altitudes:
- on the Main Alpine Ridge and south of there as well as in the Jura: mostly 5 to 10 cm
- elsewhere less or mostly dry
Temperature
At midday at 2000 m, between -2°C in the north and -4°C in the south
Wind
South to southwesterly
- moderate to strong, dropping briefly in the first half of the day on Saturday
- moderate foehn wind in the north
Outlook to Monday
Sunday
In the north, there will be broken cloud cover with occasional light precipitation. The southern flank of the Alps will be overcast and 10 to 20 cm of snow will fall down to low altitudes. There will be a moderate wind from southerly directions at high altitudes.
Avalanche risk will increase in the south, but there will be no significant change elsewhere.
Monday
In the north, there will be broken to heavy cloud cover with very little precipitation falling as snow down to low altitudes. In the inneralpine regions, there will be some sunny intervals over the course of the day, while conditions will be mainly sunny on the southern flank of the Alps with moderate northerly winds. There will be no significant change in avalanche risk.