Gotthard area
Uri Rot Stock
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
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 can still be triggered very easily by people in many places in the Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary. Remote triggering is 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 can become large.
The 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 also 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. These may still be triggered in some places, especially where there is little snow and at transitions from a deep to shallow snowpack.
Weather review for Saturday
Conditions were sunny in the mountains. High clouds gathered in the west in the afternoon.
Fresh snow
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Temperature
At midday at 2000 m, around -4 °C
Wind
Mostly light from the south to southwest
Weather forecast to Sunday
It will be quite sunny in the mountains.
Fresh snow
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Temperature
At midday at 2000 m, around -4 °C
Wind
Winds will be mostly light from variable directions.
Outlook to Tuesday
In the north, it will be quite sunny in the mountains on Monday and Tuesday. It will be very cloudy on the southern flank of the Alps on both days. On Monday, precipitation will set in here as the day progresses and will continue until Tuesday afternoon. Above 1200 m, 10 to 20 cm of snow will fall on the Main Alpine Ridge and south of there. Up to 30 cm is possible from the Lukmanier Pass to the Bernina Pass. There will be moderate southwesterly winds at times on Monday. On Tuesday, there will be moderate to strong southwesterly winds in the regions exposed to the foehn wind in the north and generally at high altitudes.
The avalanche danger will continue to decrease slowly on Monday, but only very slowly in the inneralpine regions and in the south due to the weak Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary. With fresh snowfall and wind, the avalanche danger will increase again somewhat on Tuesday on the Main Alpine Ridge and south of there, otherwise it will remain largely unchanged. Naturally triggered avalanches and avalanches triggered by human activity are expected in areas with new fallen snow. Caution and restraint are still required, especially in these regions.