Central Grisons and Anterior Rhine
Rheinwald
Updated off-schedule
The provider reissued this bulletin at 20 Oct 15:00 UTC, outside the normal publication cycle.
Hard-to-read day. Considerable, with new snow and persistent weak layers in play — you can read the surface problem; the buried one sets the consequence.
Day Risk Profile
Avalanche Problems
New snow + Persistent weak layers
3=
Field notes
New snow
Easy to spot - the snow is fresh. Look at recent avalanche activity in similar terrain, and pay attention to how much new snow has fallen in the last three days. Critical loading depends on temperature, wind, and what was on the surface before the storm. SLF advises waiting until the Snow deposited on the ground in a multiplicity of layers.EAWS glossary has had time to bond before committing to steep terrain in fresh snow.
Persistent weak layers
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
Snow deposited on the ground in a multiplicity of layers.EAWS glossary
Over the past two weeks, some snow fell in the high mountains, with the largest amounts along the main Alpine ridge from the Monte Rosa region to the Bernina region. This snow has partly undergone faceting. Further snowfall is expected on Wednesday. On shady slopes in the high mountains, the fresh snow will fall on a partly continuous Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary. In these areas, fractures may occur at the interface between the old and fresh snow, particularly on glaciers. Elsewhere, the snow will generally fall on bare ground. In these areas, 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 most likely to occur within the fresh snow and wind slabs.
Outlook
Thursday
During the night to Thursday, some precipitation will persist in the north. During the day, it will be mostly sunny, but remain cloudy in the east. The wind will be moderate to strong from the northwest.
The danger of dry avalanches will gradually decrease. Wet loose snow avalanches are to be expected on steep sun-exposed slopes in the high mountains.
Friday
On Friday, it will be variably cloudy with occasional precipitation, especially in the west. In the east, it will remain dry with sunny intervals. The snowfall level will be around 1500 m. The southwesterly wind will strengthen, reaching storm force, with a southerly foehn in the Alpine valleys.
The southwesterly wind may give rise to wind slabs that are prone to triggering. In the high mountains, people can still trigger avalanches, particularly on steep north-facing slopes.