Gotthard area
Uri Rot Stock
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.
Wet snow + Gliding snow
1
Field notes
Wet snow
Rolling snowballs, deep penetration when you step or ski, and small natural slides are clear signals that the Snow deposited on the ground in a multiplicity of layers.EAWS glossary is losing strength. After a clear, cold night the surface often freezes into a strong supporting Layer of hard-compacted snow resulting from a melt-freeze process or wind.EAWS glossary, and conditions are favourable in the early morning. After a warm, overcast night, the problem may be present from the start of the day. Plan early returns and watch the runout zones below you.
Gliding snow
Almost impossible to predict precisely, even when the warning signs are visible. A crack visible on the snowpack surface formed by snow-gliding on steep, and particularly grass-covered slopes. Areas below slopes with visible glide cracks should be avoided whenever possible due to threat of gliding sluffs or avalanches.EAWS glossary — gaps that open in the Snow deposited on the ground in a multiplicity of layers.EAWS glossary down to the ground — are often precursors to release, but they don't tell you when. A glide avalanche can release minutes after the cracks appear, or weeks later, or not at all. Some release without any visible warning. Avoid lingering anywhere near glide cracks: above them, alongside them, or below in the runout.
Snowpack & Weather
Snowpack
In many places, the fresh and drifted snow layers from last weekend and Monday are lying on weakly bonded old snow. 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 located in particular on northern and sometimes on eastern slopes above around 2400 m. On the northern flank of the Alps, they are sometimes directly beneath the new and drifted snow layers and sometimes also in the middle of the snowpack. In inneralpine regions and in northern Grisons, they are sometimes also in the lower part of the snowpack.
The Snow deposited on the ground in a multiplicity of layers.EAWS glossary has been moistened by rain below 2400 m and is saturated up to around 2100 m. Isolated Avalanche of wet snow masses. Flowing more slowly than dry avalanches; usually for shorter runout distances, however with greater impact on obstacles due to higher snow density.EAWS glossary are possible with the sunshine and rising temperatures during the daytime. Isolated gliding avalanches are still possible.
Weather review for Wednesday
After a clear night, conditions were sunny in the mountains during the day.
Fresh snow
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Temperature
At midday at 2000 m, around +4°C in the south and up to +6°C in the north
Wind
Light to moderate from southwesterly directions
Weather forecast to Thursday
The night will be partly cloudy. During the day it will be partly cloudy, becoming very sunny as the day progresses, especially in the inneralpine regions and in the south.
Fresh snow
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Temperature
At midday at 2000 m, around +3°C
Wind
Mainly light
Outlook
Skies will clear overnight to Friday and conditions will be sunny on Friday and Saturday. It will remain mild and winds will be mostly light.
The danger of dry avalanches will slowly decrease. Each day, the danger of wet avalanches will vary, becoming somewhat higher as the day progresses. Isolated gliding avalanches will be possible on steep grassy slopes.