Upper Valais
Turtmanntal
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.
Snowpack & Weather
Snowpack
In Lower Valais, northern Valais and the Bernese Oberland, there is as much snow at high altitudes as usual for this time of year, but less in other regions. There is particularly little snow on the southern flank of the Alps and at intermediate altitudes on the eastern part of the northern flank of the Alps. 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 deposited on the ground in a multiplicity of layers.EAWS glossary are located in particular on northern and eastern slopes above approximately 2400 m. Hardly any avalanches have been triggered in the last four days, except in southern Lower Valais. Here, human activity has triggered isolated avalanches in the weak Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary.
Below approximately 2800 m, the surface of the Snow deposited on the ground in a multiplicity of layers.EAWS glossary is stable on very steep southern slopes, otherwise it is mostly brittle. Only on north-facing slopes sheltered from the wind is there still some loose, faceted snow at high altitudes. With increasing southerly winds, Monday will see small local snowdrift accumulations build up over the course of the day.
Isolated wet snow slides and gliding avalanches are possible with the sunshine and rising temperatures during the daytime.
Weather review for Sunday
Conditions were sunny and mild in the mountains.
Fresh snow
-
Temperature
At midday at 2000 m, around +5 °C in the north and +3 °C in the south
Wind
Mostly light southwesterly to westerly winds
Weather forecast to Monday
It will be mostly sunny in the mountains, with high broken cloud gathering in the afternoon in the south-west and south.
Fresh snow
-
Temperature
At midday at 2000 m, between +5 °C in the north and 0 °C in the south
Wind
- Light to moderate south to southwesterly, becoming moderate to strong as the day progresses
- Moderate to strong foehn wind from the south over the course of the day in the Alpine valleys on the northern flank of the Alps
Outlook
On Tuesday it will mostly be very cloudy with foehn-like bright spells in the east. Slight precipitation will set in on Tuesday morning on the main Alpine ridge in Valais and in the south and will continue until Wednesday morning. The snowfall level will rise from 1200 m on Tuesday to around 1600 m on Wednesday. Five to 10 cm of snowfall is expected, with up to 20 cm from Saas to the Simplon Pass and locally in north-western Ticino. There will be a moderate to strong southerly wind, with a moderate to strong foehn wind from the south in the Alpine valleys on the northern flank of the Alps. On Wednesday, conditions will be mostly sunny in the west and Valais and there will be sunny intervals in the east. It will be mostly very cloudy in the south. Winds will generally die down and be mostly light.
Avalanche danger will increase slightly on Tuesday with fresh snow in the south and Snow being lifted from the snow surface and transported by wind just above the snow surface (visibility not noticeably reduced).EAWS glossary in the north. The danger will not change significantly on Wednesday.