Central Grisons and Anterior Rhine
Domleschg - Lenzerheide
Hard-to-read day. Moderate, with wind slab and persistent weak layers in play — part of it readable at the surface, part of it buried and silent.
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
With new snow and a northerly wind, additional wind slabs will form. These are medium-sized on the northern flank of the Alps and in northern Grisons, otherwise rather small. The new snow and wind slabs of the last few days are overlying an Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary whose upper part contains coarse-grained 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, especially on north- and east-facing slopes at high altitudes.
Weather review for Friday
Following a break during the night, intermittent snowfall resumed during the day. The snowfall level was around 1300 m.
Fresh snow
In the two days from Wednesday evening to Friday afternoon above approximately 2000 m:
- Extreme west of Lower Valais and between Davos, Val Müstair and Upper Engadine: 20 to 40 cm
- Elsewhere a widespread 10 to 20 cm, less in the Upper Valais and Ticino
Temperature
At midday at 2000 m, around -2 °C
Wind
Still moderate during the night, mostly light during the day from westerly directions
Weather forecast to Saturday
Snow will fall in the north. In the inneralpine regions, it will be partly cloudy with showers and longer sunny spells. The snowfall level will be 1200 m. It will be mostly sunny in the south.
Fresh snow
From Friday afternoon to Saturday afternoon, the following amounts of fresh snow are expected above approximately 2000 m:
- Northern Alpine ridge from the Wildstrubel to Liechtenstein, northern Grisons: 15 to 25 cm
- Remaining northern flank of the Alps, Lower Valais, remaining parts of Grisons: 5 to 15 cm
- Upper Valais and Ticino: less or no snow
Temperature
At midday at 2000 m, between -3 °C in the north and 0 °C in the south
Wind
Strong at times on the Main Alpine Ridge, elsewhere mostly moderate from the northwest
Outlook to Monday
After a mostly clear night, it will be quite sunny on Monday with cumulus clouds developing as the day progresses. The zero-degree level will be 2200 m in the north and 2500 m in the south. Winds will be mostly light. Sunday night into Monday will be partly overcast. In the late morning, there will still be some bright spells in the east, while elsewhere there will be showers and isolated thunderstorms. The snowfall level will be around 2000 m. The winds will be light to moderate from the west.
The danger of dry avalanches will decrease, but only slowly on very steep north-facing slopes in the Areas above approximately 3000 m (particularly glaciated areas).EAWS glossary. As a consequence of solar radiation and daytime warming, the danger of wet avalanches will increase somewhat as the day progresses. In particular, near-surface moist avalanches caused by the fresh snow of recent days are to be expected.