Bernese Oberland
Lenk
Avalanche Problems
Wind slab + Persistent weak layers
2+
Field notes
Wind slab
Look for fresh snow deposits on Slope facing downwind/ wind sheltered aspect. Snow deposits can attain several times average snow depth.EAWS glossary, in Usually a steep, elongated, eroded trench; typically prone to snowdrift accumulation.EAWS glossary and Rounded or elongated concavity; typically tending to accumulate snowdrift.EAWS glossary, and behind ridgelines and abrupt changes in terrain — these are where the wind has loaded the snow into slabs that are easy to trigger. Recent avalanches, shooting cracks under your weight, and 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 are clear confirmations of the problem. The safest move is to avoid wind-loaded terrain entirely. NB wind signs alone don't always mean an avalanche problem exists, and the age of drifted snow is hard to judge.
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.
Gliding snow
2+
Field notes
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
Snow depths are well above average in the west and north, with more than twice as much snow as usual for this time of year in places. In other regions, there is a widespread 50 to 100% of the usual amount of snow and only 30 to 60% on the southern flank of the Alps.
Deep layers of the Snow deposited on the ground in a multiplicity of layers.EAWS glossary are faceted and weak, especially on shady slopes above approximately 2400 m and generally in Areas above approximately 3000 m (particularly glaciated areas).EAWS glossary. In regions with deep snow in the west and north, these 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 now thickly overlaid and are therefore no longer so easily triggered by winter sports participants. However, any avalanches triggered in these deep layers can still become large. In regions with little fresh snow, avalanches are easier to trigger in deep layers of old snow and will usually be of medium size.
Small to medium gliding avalanches are still expected in the west and north.
Weather review for Saturday
Overnight to Saturday, a few centimetres of snow fell in the east above approximately 1500 m. During the day, conditions were sunny in the west and south and increasingly sunny in the east.
Fresh snow
A few centimetres in the east, otherwise dry
Temperature
Around 0°C at midday at 2000 m in the east and +3°C in the west and south
Wind
Mostly light from westerly directions
Weather forecast to Sunday
Clouds will rapidly gather overnight to Sunday. There will be brighter intervals during the day, especially in northern and central Grisons and Lower Engadine. Elsewhere it will be mostly cloudy. In the afternoon, light snowfall will set in in the north-west above approximately 1400 m.
Fresh snow
A few centimetres in the west on Sunday afternoon
Temperature
At midday at 2000 m, around 0°C
Wind
The southwesterly wind will be moderate in the west, otherwise mostly light. In the Jura, there will be a strong westerly wind at times in the afternoon.
Outlook
Around 5 cm of snow will fall in the north overnight to Monday. The snowfall level will drop to 900 m. Some clouds will remain during the day along the Prealps and in the east while conditions will be mostly sunny in the mountains. On Tuesday, conditions will often be cloudy on the southern flank of the Alps but elsewhere mostly sunny. The zero-degree level will be around 2000 m. There will be a light southerly wind on both days.
Avalanche risk will continue to fall. Gliding avalanches are still possible in regions with deep snow in the west and north.