Churfirsten and Rhine Valley
Flumserberg
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
On shady slopes above approximately 2400 m and in the Areas above approximately 3000 m (particularly glaciated areas).EAWS glossary in general, there are faceted 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 the west, these are heavily overlaid and therefore only triggered occasionally. In the other regions, they are closer to the surface. However, the overlying layers have since undergone a structural transformation and have become softer. For this reason, only isolated fractures have been reported here as well.
In many places, there is some loose fresh snow lying on the surface from the last 3 days and some Transparent, frequently flat crystals forming on the snowpack when moist air settles on the surface. It forms most often during cold, clear, humid nights. Once it is blanketed by fresh fallen snow, surface hoar is one of the most critical weak layer. See also: www.snowcrystals.itEAWS glossary (hoar frost). These will be transported on Saturday during the course of the day.
Weather review for Friday
During the night, a little snow fell above approximately 900 m. During the day, it became quite sunny in the south and generally in the Areas above approximately 3000 m (particularly glaciated areas).EAWS glossary; elsewhere it remained mostly cloudy.
Fresh snow
10 cm in some localities in Grisons, less elsewhere
Temperature
At midday at 2000 m, between -4 °C in the north and -2 °C in the south
Wind
Light to moderate from northerly directions
Weather forecast to Saturday
In the south, on the Main Alpine Ridge and in Grisons it will be quite sunny, while elsewhere it will be mostly cloudy but mainly dry.
Fresh snow
-
Temperature
At midday at 2000 m, around +1 °C
Wind
There will be a westerly wind that will be:
- Mostly light overnight
- Increasingly strong during the day in the north and in the Areas above approximately 3000 m (particularly glaciated areas).EAWS glossary of Valais
Outlook until Monday
It will be very cloudy and precipitation will fall during the night. The snowfall level will rise from 1500 m to 2300 m. In the north and Valais, 20 to 40 cm of snow will fall at high altitudes, and up to 50 cm will fall from the Bernese Oberland to central Switzerland. Less snow will fall in Grisons and it will remain dry in the far south. There will be a westerly wind, which will be strong in the north but moderate elsewhere. On Monday, it will be sunny and mild and the wind will ease.
On Sunday, the danger of dry avalanches will increase at high altitudes. Below approximately 2300 m, the danger of wet and gliding avalanches will increase with the rain. In the west and north, danger level 3 (considerable) will be reached in many places over the course of Sunday. On Monday, the avalanche danger will decrease below approximately 2300 m, but will not change significantly at higher altitudes.