Bernese Oberland
Brienz-Interlaken
Day Risk Profile
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
The snowfall in the north will intensify overnight to Tuesday. The strong to storm force northerly wind will transport the new snow and in some places also the loose old snow. Snowdrift accumulations will be widespread, with large ones forming in the north. In places that are protected from the wind, the new snow will be deposited on the still loose snow from the weekend.
In the upper part of the Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary, there are some 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 and some snow-covered Transparent, frequently flat crystals forming on the snowpack when moist air settles on the surface. It forms most often during cold, clear, humid nights. Once it is blanketed by fresh fallen snow, surface hoar is one of the most critical weak layer. See also: www.snowcrystals.itEAWS glossary, particularly on shady slopes. At the weekend, avalanches were triggered in these weak layers by winter sports participants. These weak layers are still prone to triggering. In the inneralpine regions of Valais and particularly Grisons, weak layers deeper in the Snow deposited on the ground in a multiplicity of layers.EAWS glossary are still prone to triggering in places and it is also possible for isolated avalanches to be triggered in near-ground weak layers.
Weather review for Monday
Except in the far south, it was mostly heavily overcast and light snowfall began in the early morning, intensifying during the course of the day. The snowfall level was between 500 and 900 m. It was sunny in central and southern Ticino.
Fresh snow
- Northern flank of the Alps from the eastern part of the Bernese Alps to the Alpstein region, northern Grisons: 10 to 20 cm
- Elsewhere a few centimetres, dry in central and southern Ticino
Temperature
At midday at 2000 m, between -3 °C in the west and south and -6 °C in the east.
Wind
- During the night into Monday, moderate northerly winds at high altitudes
- Wind shifted from a westerly to northwesterly during the day and was moderate to strong; in the afternoon, it was strong to storm force at high altitudes
Weather forecast to Tuesday
In the north, it will be mostly very cloudy, and snow will fall down to low altitudes. In the areas of orographic lift on the northern flank of the Alps, the snowfall will be persistent and heavy until the late morning, becoming increasingly showery as the day progresses. Conditions will be mostly sunny south of the Main Alpine Ridge.
Fresh snow
- Northern flank of the Alps from Wildstrubel to the Glarus Alps excluding the Prealps: 40 to 60 cm
- Remaining areas on the northern flank of the Alps, Lower Valais, northern Upper Valais, southern Obergoms, southern Urseren, northern and central Grisons, northern Engadine: 20 to 30 cm, locally up to 40 cm
- Remaining southern Upper Valais, northern Ticino 10 to 20 cm
- Further south a few centimetres or dry
Temperature
At midday at 2000 m, around -8 °C in the north and -5 °C in the south
Wind
- Moderate to strong, becoming a strong to storm force northerly on the alpine ridgelines
- Moderate to strong foehn wind in the south
Outlook
Wednesday
In the north there will be broken cloud cover with showers. The snowfall level will be between 400 m and 700 m. On the northern flank of the Alps, a further 10 to 20 cm will fall, with 5 to 10 cm falling in the Jura and northern and central Grisons. It will be mostly sunny in Valais and the south. Overnight to Wednesday, the wind will still be moderate to strong from the northeast but ease off during the course of the day. In the Jura, there will be moderate to strong Bise winds as the day progresses.
The danger of dry avalanches will decrease and naturally triggered dry avalanches will be highly unlikely. However, the situation will remain critical for snow sports outside marked and open pistes. As a result of the solar radiation, moist loose snow avalanches are to be expected from the fresh snow. South of the Main Alpine Ridge, the avalanche danger will not change significantly.
Thursday
After a mostly clear night, conditions will be sunny in the mountains with patches of cloud. The zero-degree level will rise to around 1600 m in the north and 2200 m in the south, and the wind will be light to moderate from the north-east.
The danger of dry avalanches will decrease. During the course of the day, moist loose snow avalanches from the loose snow and increasingly also gliding avalanches are to be expected.