Central Prealps
Gersau
Manageable day. Moderate, with wind slab and wet snow at the surface — the evidence is there to read before you commit to a slope.
Day Risk Profile
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.
Wet snow
1
Field notes
Rolling snowballs, deep penetration when you step or ski, and small natural slides are clear signals that the Snow deposited on the ground in a multiplicity of layers.EAWS glossary is losing strength. After a clear, cold night the surface often freezes into a strong supporting Layer of hard-compacted snow resulting from a melt-freeze process or wind.EAWS glossary, and conditions are favourable in the early morning. After a warm, overcast night, the problem may be present from the start of the day. Plan early returns and watch the runout zones below you.
Snowpack & Weather
Snowpack
The sometimes large amounts of new snow and wind-drifted snow in the extreme west of Lower Valais, in the north, and in large parts of Grisons are in some cases still prone to triggering. In the other regions, more recent snowdrift accumulations are in some cases still prone to triggering, but are mostly smaller. In addition, avalanches can be triggered in the upper layers of the underlying Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary, especially on north- and east-facing slopes.
As a consequence of solar radiation, numerous loose snow avalanches are to be expected from the new fallen snow, especially in the regions exposed to heavier precipitation.
Weather review for Saturday
In the north and in Grisons, snow fell above approximately 1300 m, increasingly in the form of showers during the day. In Valais, conditions were changeable with extended bright spells. In the south, conditions were very sunny.
Fresh snow
From Friday afternoon to Saturday afternoon, the following amounts of fresh snow fell above approximately 2000 m:
- Northern Alpine ridge from the Wildstrubel to the St. Gallen Alps: 20 to 30 cm
- Rest of the northern flank of the Alps, Lower Valais, northern Grisons, Engadine, Val Müstair: 10 to 20 cm, less elsewhere
Over the three days from Wednesday evening to Saturday afternoon, altitudes above approximately 2000 m thus saw the following snowfall:
- Extreme west of Lower Valais, northern Alpine ridge excluding the Alpstein-Alvier area and Liechtenstein, as well as northern Grisons, Engadine, Val Bregaglia, Val Poschiavo, Val Müstair: mostly 30 to 50 cm, with up to 70 cm in places in the Areas above approximately 3000 m (particularly glaciated areas).EAWS glossary
- Rest of the northern flank of the Alps, rest of Lower Valais: 15 to 30 cm
- Less elsewhere, no snow in the far south
Temperature
At midday at 2000 m, between -3 °C in the north and +2 °C in the south
Wind
Moderate to strong along the central and eastern Main Alpine Ridge, otherwise light to moderate from northerly directions
Weather forecast to Sunday
After a mostly clear night, it will be quite sunny. As the day progresses, there will be cumulus clouds and an increasing amount of high-level cloud cover.
Fresh snow
-
Temperature
At midday at 2000 m, between 0 °C in the north and +3 °C in the south
Wind
Shifting to southwesterly and mostly light
Outlook to Tuesday
Sunday night into Monday will be partly clear in the east, and cloudy elsewhere. In the morning, there will still be bright spells in the east; elsewhere, it will be mostly cloudy with showers, especially along the northern flank of the Alps. The snowfall level will be just below 2000 m. On Tuesday, it will initially be sunny in the west after a mostly clear night. As the day progresses, clouds will gather. In the east, after a cloudy night, some residual cloud will remain in the morning. After that, there will be brighter intervals. Conditions will be very sunny in the south. On both days, the wind will blow from westerly directions and will remain moderate at times in the north on Monday, and light on Tuesday. The zero-degree level will be 2200 m in the north and 2500 m in the south, gradually rising a little as the day progresses on Tuesday.
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. Wet avalanches are to be expected in the near-surface layers on very steep terrain, particularly as a consequence of solar radiation.