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
Snow depths are above average in the west and north, where there is a widespread 150 to 200% of the usual amount of snow. In other regions, there is a widespread 50 to 100%, of the usual amount of snow and less than 50% on the southern flank of the Alps.
Especially on shady slopes above approximately 2400 m and generally in the Areas above approximately 3000 m (particularly glaciated areas).EAWS glossary, there are faceted, long-lasting 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 deep in the Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary. In many places in western and northern regions with heavy snow, these layers are overlaid with deep fresh snow and so can no longer be easily triggered by winter sport participants. However, any avalanches that are triggered in these deep layers can still become large, as has been clear from the avalanches in recent days. In regions with little fresh snow, avalanches can more easily be triggered in deep layers of old snow and will usually be of medium size.
Small to medium gliding avalanches are still to be expected in the west and north.
Weather review for Sunday
Conditions were cloudy but mostly dry on Sunday
Fresh snow
-
Temperature
At midday at 2000 m in the east around +1°C
Wind
Winds were mostly light and occasionally moderate from the south.
Weather forecast to Monday
There will be little snowfall overnight to Monday, except in the very south. The snowfall level will drop from 1500 m to 800 m. Some clouds will remain along the Prealps and in the east during the day. Conditions will be sunny in the west and generally at high altitude. Clouds will gather in the south as the day progresses.
Fresh snow
From Sunday afternoon to Monday morning above approximately 1600 m:
- northern flank of the Alps: 5 to 10 cm
- other regions less or dry
Temperature
At midday at 2000 m, around -2°C
Wind
Mostly light from southerly directions
Outlook
On Tuesday and Wednesday there will be low stratus cloud in the north with only occasional sunny spells due to the broken, higher altitude cloud cover. Most of the sunshine will be in the east with a slight tendency towards foehn winds. Conditions will be mainly cloudy on both days on the southern flank of the Alps. A few centimetres of snow may fall above approximately 1400 m on Wednesday. There will be a light to moderate southerly wind on both days.
Avalanche risk will continue to fall. Avalanches, possibly large, may still be triggered in the Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary, especially on steep shady slopes at high altitudes. Gliding avalanches are still possible in regions with deep snow in the west and north.