Upper Engadine and Silvretta
Sur Tasna
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
In the regions south of a line from the Rhône to the Rhine, the 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 that have been a feature since the beginning of January are still present. The number of places where avalanches can be triggered by human activity in the weak layers of the Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary are continuing to decrease. However, any avalanches may still become large.
In the regions north of a line from the Rhône to the Rhine and in the extreme west of Lower Valais, 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 Snow deposited on the ground in a multiplicity of layers.EAWS glossary are mostly thickly covered. Triggering by human activity is unlikely.
As a consequence of the falling temperatures, the continued moistening of the Snow deposited on the ground in a multiplicity of layers.EAWS glossary and deeper 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 is slowing down. Gliding avalanche activity is continuing to decrease. Gliding avalanches can however become large, especially in the snowier west.
Weather review for Tuesday
Monday night into Tuesday was partly cloudy in the north and very cloudy in the south with little precipitation. During the day, it was mostly very cloudy on the western part of the northern flank of the Alps, in Valais and on the southern flank of the Alps, while elsewhere it was mostly sunny.
Fresh snow
A few centimetres above 1500 m on the Main Alpine Ridge between Zermatt and the Bernina Pass
Temperature
At midday at 2000 m, between +3 °C in the north and -1 °C in the south
Wind
From the south: generally light, but increasing to moderate in the regions exposed to the foehn wind in the north as the day progresses
Weather forecast to Wednesday
Tuesday night into Wednesday will be partly cloudy with bright spells. There will be a little precipitation on the northern and southern flanks of the Alps, falling as snow above approximately 1600 m. During the day, it will be mostly sunny in the inneralpine regions of Valais and Grisons. On the northern flank of the Alps it will be partly sunny, whereas on the southern flank of the Alps, it will be very cloudy.
Fresh snow
Along the Prealps and on the southern flank of the Alps: a few centimetres above approximately 1600 m
Temperature
At midday at 2000 m, between +1 °C in the north and -1 °C in the south
Wind
From the southwest: initially mostly light, becoming increasingly moderate to strong in the Jura and along the Prealps as the day progresses
Outlook to Friday
Overnight to Thursday, it will be mostly cloudy and there will be widespread light snowfall above approximately 1400 m in the north. During the day, it will gradually clear up in the west and south, but it will only be partly sunny on the central and eastern parts of the northern flank of the Alps and in northern Grisons. The wind will be mostly light and shift from a southerly to a northerly. Thursday night into Friday will be mostly clear. During the day it will be mostly sunny in the north and partly sunny in the south. The southwesterly wind will pick up as the day progresses. It will be appreciably milder in the north.
The danger of dry avalanches will increase slightly on Thursday, especially on the northern flank of the Alps. Elsewhere, it will not change significantly. The danger of wet and gliding avalanches will increase a little during the course of the day, especially in the north on Friday. Touring and off-piste descents should be completed in good time.