Upper Engadine and Silvretta
Östliche Silvretta
Day Risk Profile
Avalanche Problems
Wind slab + Persistent weak layers
2+
Field notes
Wind slab
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.
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
Sunday's layers of new and drifted snow are becoming increasingly stable. The number of places where avalanches can be triggered in these layers is decreasing. Western Ticino and the western and central parts of the northern Alpine ridge have seen the largest volumes of new and drifted snow. The probability of triggering in buried 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, which is primarily present in southern Valais and in Grisons, is also decreasing.
Isolated avalanches are repeatedly being triggered in near-ground 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 inneralpine regions and southern parts of Grisons. These avalanches may still become large. In other regions, although there are still weak layers in the near-ground Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary on shady slopes, they are mostly so thickly covered that they are very unlikely to be triggered.
With warming and solar radiation on Tuesday, there may be loose snow slides originating from near-surface snow layers, especially in rocky terrain.
Weather review for Monday
Overnight to Monday and during the day there was a little snowfall, especially in the north above 1400 m. There were sunny spells in the west and south, but cloud cover was heavier towards the east.
New snow
-
Temperature
At midday at 2000 m, between -3 °C in the north and 0 °C in the south
Wind
Northerly:
- moderate at times on the northern Alpine ridge and on the main Alpine ridge
- elsewhere light
Weather forecast to Tuesday
After a mostly clear night, conditions will mainly be sunny during the day.
New snow
-
Temperature
Rising, reaching around 0 °C at midday at 2000 m
Wind
Mostly light from northerly directions
Outlook to Thursday
After a partly clear night into Wednesday, cloud cover will increase from the west in the morning. Conditions will initially remain mostly sunny, especially in the east and south. Later on, cloud cover will increase there as well while, in the north, precipitation will set in over the course of the afternoon. By the evening, 10 to 20 cm of snow will have fallen on the northern flank of the Alps; elsewhere less. The snowfall level will rapidly drop from 1200 m to low altitudes by the evening. Winds will rise appreciably in the morning, becoming strong to storm force in the north and west, while in the south and in Grisons they will be moderate to strong from westerly directions at high altitudes.
On Thursday, there will be widespread snowfall down to low altitudes in the north, and this will be persistent in Lower Valais and on the northern flank of the Alps where 30 to 50 cm of snow will fall above 2000 m; elsewhere less. There will be a storm-force northwesterly wind in the mountains. In the far south, conditions will be dry with sunny intervals in a strong northerly foehn wind.
Avalanche danger will increase, markedly so in the north over the course of the day from Wednesday onwards.