Upper Engadine and Silvretta
Zuoz
Day Risk Profile
Avalanche Problems
Persistent weak layers
3=
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
Last week's fresh and drifted snow is lying on a weak Snow deposited on the ground in a multiplicity of layers.EAWS glossary on the Main Alpine Ridge and south of there and also in the Engadine. In these regions, medium-sized and even large avalanches may still easily be triggered by human activity in the Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary in many places. Remotely triggered avalanches are to be expected. Avalanches may also be triggered deeper in the snowpack in southern Valais and in the inneralpine regions of Grisons, especially on northern and eastern slopes. Here, too, some avalanches may become large.
Snow deposited on the ground in a multiplicity of layers.EAWS glossary structure is somewhat more favourable on the northern flank of the Alps and in northern Valais, but there are 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 deeper in the snowpack in these regions too. These may still be triggered in some places, especially where there is little snow and at transitions from a deep to shallow snowpack.
Snowdrift accumulations prone to triggering can develop in southerly winds later in the day.
Weather review for Sunday
Conditions were mostly very sunny in the mountains.
Fresh snow
-
Temperature
At midday at 2000 m, around -4°C
Wind
Moderate northerly winds during the night in the south, otherwise mostly light
Weather forecast to Monday
In the west and south, there will be sunny intervals while elsewhere it will be mostly sunny.
Fresh snow
-
Temperature
At midday at 2000 m, between 0°C in the north and -6°C in the south
Wind
Southwesterly winds will rise to moderate to strong at high altitudes over the course of the day
Outlook to Wednesday
On the central part of the Main Alpine Ridge and south of there, there will be often heavy cloud cover on Tuesday and Wednesday, with snow falling down to low altitudes. The largest volumes of snow will fall on the central part of the southern flank of the Alps and from the Lukmanier Pass to the Bernina Pass. By Wednesday afternoon, 20 to 30 cm of fresh snow is expected to have fallen in these regions. There will be a strong southerly wind at high altitudes on Tuesday. Significant 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 mean that danger level 4 may be reached in these regions despite the modest amount of fresh snow. Naturally triggered avalanches, some large, are expected. The danger exists primarily in alpine snow sports terrain. Avalanches capable of reaching valley bottoms are unlikely.
In the north, there will be sunny intervals on both days with strong to storm-force southerly winds at high altitudes, especially on Tuesday, while there will be a strong foehn wind in the Alpine valleys of the north. The strong winds mean that avalanche risk will increase somewhat in some regions. The avalanche situation remains critical, particularly in the inneralpine regions of Valais and Grisons.