Bernese Oberland
Brienz-Interlaken
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.
Wet snow + Gliding snow
2
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 the regions situated north of a line Rhône-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 and are hardly triggerable by human activity.
In the regions situated south of a line Rhône-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. However, the number of avalanche-prone locations has decreased significantly. Reports of avalanches and alarm signs indicate that the situation in Grisons remains the most precarious.
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 lower part of the Snow deposited on the ground in a multiplicity of layers.EAWS glossary are being weakened as they become moistened for the first time. Wet The abrupt release of a slab of snow on a mountain slope. After crack initiation and crack propagation in a weak layer the released slab comprises 3 elements: The weak layer, the gliding horizon and the slab. If the slope angle is steep enough, the slab will glide down. If the slope is not steep enough, the slab will settle down on the failed weak layer. Possibly a whumpf sound will follow due to air pressed out of the weak layer. The fracture line will be sharp edged.EAWS glossary are possible as the day progresses. These can occur naturally but can also be triggered by winter sports participants, at present mainly on sunny slopes below approximately 2800 m.
Weather review for Thursday
After a clear night, it was mostly sunny and mild. The sky was somewhat obscured by Sahara dust, especially in the west.
Fresh snow
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Temperature
At midday at 2000 m, between +7 °C in the northwest and +2 °C in the south
Wind
Mainly light, sometimes moderate from the south at high altitudes and in the foehn valleys
Weather forecast to Friday
The outgoing longwave radiation during the night will be reduced somewhat by high clouds. It will be quite sunny during the day, especially in the east. However, there will be sometimes denser medium and high cloud cover and visibility will be obscured by Sahara dust.
Fresh snow
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Temperature
At midday at 2000 m, around +5 °C in the north and +2 °C in the south
Wind
Mainly light from the south to southeast
Outlook to Sunday
The nights will be partly clear. However, the cloud cover is uncertain due to the Sahara dust. On Saturday, it will be quite sunny despite cirrostratus clouds and obscured visibility due to Sahara dust. On Sunday, it will be increasingly cloudy in the south. There will be cumulus clouds in the Jura and along the Prealps. Otherwise it will remain quite sunny. On Saturday, the zero-degree level will be around 2700 m in the north and 2200 m in the south. On Sunday, it will drop by around 200 m. The winds will be mainly light.
The danger of dry avalanches will continue to decrease, but only slowly in Grisons due to the weak Snow deposited on the ground in a multiplicity of layers.EAWS glossary structure. Each day, the danger of wet avalanches will increase as the day progresses. Where outgoing longwave radiation has reduced during the night, the danger will increase in the morning. Touring and off-piste descents should be completed in good time.