Vaud Alps
Aigle-Leysin
Stable day. Low, with wet snow and gliding snow named together — one of them visible at the surface, the other buried.
Day Risk Profile
Avalanche Problems
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
Despite the high air temperature, the dry air means that the surface of the Snow deposited on the ground in a multiplicity of layers.EAWS glossary will freeze during the clear night into Saturday to become capable of bearing loads. Sunshine will cause it to soften quickly.
Moisture penetration into the Snow deposited on the ground in a multiplicity of layers.EAWS glossary is well advanced. The most precarious areas are slopes where 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 layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary are becoming wet for the first time. At present, this mainly affects north-facing slopes between approximately 2200 and 2500 m, and east- and west-facing slopes between approximately 2500 and 2800 m. On south-facing slopes, moisture penetration into the snowpack extends as far as the Areas above approximately 3000 m (particularly glaciated areas).EAWS glossary. In Grisons, the weak layers in the old snowpack are the least deeply buried, which means that 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 can also be triggered by human activity in some places.
Higher up, the Snow deposited on the ground in a multiplicity of layers.EAWS glossary is still dry. There are still 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 layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary.
In general, hardly any avalanches have been reported in recent days.
Weather review for Friday
After a clear night, conditions were sunny and mild.
Fresh snow
-
Temperature
At midday at 2000 m, between +7 °C in the north and +11 °C in the south
The zero-degree level was between 3300 m and 3500 m.
Wind
Light to moderate northeasterly
Weather forecast to Saturday
After a clear night, it will be sunny, with a few cumulus clouds developing during the course of the day. With the zero-degree level at around 3000 m, it will remain mild.
Fresh snow
-
Temperature
At midday at 2000 m, between +7 °C in the north and +9 °C in the south
Wind
Light to moderate from north to northwest
Outlook to Monday
The night into Sunday will be mostly clear, and it will be sunny during the day with high cloud cover at times. The night into Monday will be mostly clear in the north, and only partly clear in the south. On Monday it will be mostly sunny in the north and partly sunny in the south with increasing high cloud cover. A few cumulus clouds will develop during the course of each day. In the far south, isolated showers are possible during the course of Monday. The zero-degree level will be around 3000 m. The winds will be light, at times rising to moderate from northerly directions as the day progresses.
After a clear night, touring conditions will be favourable in the early morning. The danger of wet avalanches will increase appreciably as each day progresses; where there is reduced outgoing longwave radiation during the night, this will occur in the early morning. Tours and hut ascents should therefore be started early and finished in good time.