Bernese Oberland
Brienz-Interlaken
Avalanche Problems
New snow + Persistent weak layers
3=
Field notes
New snow
Easy to spot - the snow is fresh. Look at recent avalanche activity in similar terrain, and pay attention to how much new snow has fallen in the last three days. Critical loading depends on temperature, wind, and what was on the surface before the storm. SLF advises waiting until the Snow deposited on the ground in a multiplicity of layers.EAWS glossary has had time to bond before committing to steep terrain in fresh snow.
Persistent weak layers
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
With new fallen snow and sometimes strong north to northeasterly winds, snowdrift accumulations are forming that are prone to triggering. In the north, where the most snow is falling, these are large. In the other regions, they are up to medium-sized. Deeper in the Snow deposited on the ground in a multiplicity of layers.EAWS glossary, there are faceted 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 prone to triggering, especially on shady slopes above approximately 2400 m and generally in the Areas above approximately 3000 m (particularly glaciated areas).EAWS glossary. Avalanches may also be triggered in these deeper layers at times, and isolated, naturally triggered avalanches are possible.
Outlook
A little snow will fall in the north during the night into Saturday. During the day, it will be partly cloudy in the north and east, and sunny in the west and in Ticino. There will be moderate northerly to northeasterly winds, strong in the west. It will be cold with around -10 °C at 2000 m. Clouds will gather rapidly in the west on Sunday, while it will remain sunny for longer in the east. The wind will shift to the west and will be strong in the north and west, moderate in the south.
The avalanche danger will decrease only slowly. Changing winds will create snowdrift accumulations that are prone to triggering. In addition, avalanches may be triggered in deeper layers of the Snow deposited on the ground in a multiplicity of layers.EAWS glossary, especially on north-facing slopes above 2400 m and in the Areas above approximately 3000 m (particularly glaciated areas).EAWS glossary.