Central Prealps
Gersau
Avalanche Problems
Wind slab
2-
Field notes
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.
Snowpack & Weather
Snowpack
Suhday's new and drifted snow is mostly quite well bonded to the old snow surface. In the regions exposed to the most precipitation, avalanches can be triggered, mainly within the new and drifted snow. Isolated avalanches can also be triggered in the near-ground Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary. This is particularly the case on northern slopes above approximately 2800 m and in the Areas above approximately 3000 m (particularly glaciated areas).EAWS glossary in general.
As a result of sunshine and warming temperatures during the day, gliding avalanches and loose snow avalanches are to be expected.
Weather review for Sunday
There was widespread precipitation. The snowfall level in the south was around 2400 m, while in the north it dropped from 2400 m to around 2000 m.
Fresh snow
From Saturday evening to Sunday midday above approximately 2800 m:
- extreme west of Lower Valais, northern Lower Valais, central part of the southern flank of the Alps, Avers, Val Bregaglia to the Bernina region: 10 to 20 cm, locally up to 30 cm
- elsewhere a widespread 5 to 10 cm
Temperature
Falling; at midday at 2000 m between 0 °C in the northwest and +5 °C in the south
Wind
Mostly moderate southwesterly
Weather forecast to Monday
Widespread precipitation will continue into the night to Monday. The snowfall level will drop to around 1500 m in the north and around 2000 m in the south. It will be increasingly sunny during the day.
Fresh snow
From Sunday midday to Monday morning, in the north above approximately 2500 m and in the south above approximately 2800 m:
- northern Alpine ridge east of the Grimsel Pass, Grisons, Val Blenio: 15 to 30 cm
- elsewhere a widespread 5 to 15 cm
Temperature
At midday at 2000 m, around -1 °C in the north and +4 °C in the south
Wind
Strong during the night to Monday in the south and generally at high altitudes, elsewhere light to moderate northwesterly
Outlook
Tuesday and Wednesday will be mostly sunny and very mild. The zero-degree level will be at 3800 m. The danger of dry avalanches will decrease. On Tuesday in particular, loose snow avalanches and gliding avalanches are to be expected in regions where fresh snow has fallen.