Lower Valais
Montana
Day Risk Profile
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.
Snowpack & Weather
Snowpack
In the south, the weekend’s fresh and drifted snow is lying on a weak Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary, especially on shady slopes. Avalanches can be easily triggered at the transition from fresh and drifted snow to old snow. In the north, Monday’s westerly winds and the small amount of fresh snow have resulted in the development of some mostly small snowdrift accumulations, which are nonetheless prone to triggering.
There are distinct 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 deeper 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 wind-protected shady slopes. Such places are particularly common south of a line from the Rhone to the Rhine. In these weak layers, medium-sized and occasionally large avalanches can still be triggered in the old snow by human activity. North of a line from the Rhone to the Rhine, the deeper layers of the Snow deposited on the ground in a multiplicity of layers.EAWS glossary are somewhat less prone to triggering and hazardous zones are less common.
Weather review for Monday
During the night, a little snow fell in the north down to low altitudes, while during the day, conditions brightened gradually from the west. In the south, conditions were very sunny.
Fresh snow
From Sunday evening to Monday morning above approximately 800 m:
- north of a line from the Rhone to the Rhine, Prättigau, Silvretta, Samnaun: 5 to 15 cm
- otherwise a widespread few centimetres
Temperature
At midday at 2000 m, around -6°C
Wind
Mostly light at night, moderate during the day from westerly directions
Weather forecast to Tuesday
Conditions will initially be very sunny in the east and south. Otherwise, clouds will rapidly gather from the west. In the afternoon, a light scattering of snow will fall in the Jura above approximately 1500 m.
Fresh snow
-
Temperature
At midday at 2000 m, between +2°C in the north and -5°C in the south
Wind
- Initially moderate, but becoming increasingly strong from the southwest over the course of the day
- A sometimes strong foehn wind in the Alpine valleys of the north
Outlook
Wednesday
Precipitation will set in from the west and south overnight to Wednesday. During the day the north will also see occasional snowfall. The snowfall level will drop rapidly to low altitudes. Western Jura and the extreme west of Lower Valais, the Main Alpine Ridge and south of there can expect a widespread 10 to 20 cm of snow, with up to 40 cm in Val Moesa, Val Bregaglia and the Bernina region. Otherwise, a widespread 5 to 10 cm of snow is forecast. There will be strong southerly winds at night, with a strong foehn wind in the Alpine valleys. During the day, the wind will drop significantly. Avalanche risk will increase in many areas, especially significantly along the Main Alpine Ridge and south of there.
Thursday
On Thursday morning, some snow will continue to fall down to low altitudes in the east. During the day brighter periods will increasingly move in from the west and south. There will continue to be a strong westerly wind in the north during the night. During the day the wind will ease significantly and become a light to moderate westerly to northerly. Avalanche risk will barely change compared to the previous day.