Valais Chablais
Monthey-Val d'Illiez
Hard-to-read day. Moderate all day, with persistent weak layers and wet snow across the two halves — the level holds; what changes is what sits under it.
Day Risk Profile
Problem type changes as the day progresses
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
2
Field notes
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.
Snowpack & Weather
Snowpack
In Areas above approximately 3000 m (particularly glaciated areas).EAWS glossary, last week's fresh and drifted snow is lying primarily on steep north-facing slopes on 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 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. Avalanche reports from recent days confirm that these weak layers are in some cases prone to triggering.
Further saturation of the Snow deposited on the ground in a multiplicity of layers.EAWS glossary is currently scarcely progressing. Avalanche of wet snow masses. Flowing more slowly than dry avalanches; usually for shorter runout distances, however with greater impact on obstacles due to higher snow density.EAWS glossary that can sweep away the entire snowpack are therefore relatively rare. The most critical areas are north-facing slopes between 2200 and 2600 m.
Weather review for Saturday
Overnight to Saturday, some heavy showers and storms passed through in the north, but in southern Valais, Grisons and Ticino, the night sky was often clear. During the day, conditions were very sunny with some denser patches of cloud, especially in the east.
Fresh snow
A few centimetres on the northern Alpine ridge in Areas above approximately 3000 m (particularly glaciated areas).EAWS glossary
Temperature
At midday at 2000 m, around +8 °C
Wind
Light southerly, sometimes moderate overnight
Weather forecast to Sunday
There will be mostly cloudy skies overnight to Sunday. In the morning, there will be precipitation especially in the south, but also in the west during the day. The snowfall level will be around 2400 m. The east will remain mostly dry with brighter intervals.
Fresh snow
On the main Alpine ridge and south of there above 2800 m, up to 10 cm, elsewhere less or dry
Temperature
At midday at 2000 m, +6 °C in the west, +4 °C in the south and +8 °C in the east
Wind
Increasingly moderate southwesterly wind during the day
Outlook to Tuesday
There will be widespread precipitation until Tuesday morning. The snowfall level on Monday will be around 2100 m, dropping during the night to Tuesday to 1800 m, and as low as 1400 m in the northeast. On the northern Alpine ridge and in westernmost Lower Valais, a total of 20 to 40 cm of snow will fall at high altitudes, with 15 to 30 cm in Grisons. During the daytime on Tuesday conditions will be very sunny in the south and in Valais, while elsewhere cloudy intervals will continue. On Monday, there will be a moderate westerly wind, which will become increasingly strong from the afternoon onwards, reaching storm-force at times in Areas above approximately 3000 m (particularly glaciated areas).EAWS glossary. On Tuesday the wind will ease off as the day progresses.
The fresh snow and strong winds will create snowdrift accumulations that are prone to triggering. The danger of dry avalanches will increase, especially in Areas above approximately 3000 m (particularly glaciated areas).EAWS glossary. In addition, with the sunshine on Tuesday the fresh snow is expected to produce loose snow avalanches and wet snow slides.