Bernese Oberland
Hohgant
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.
Snowpack & Weather
Snowpack
Tuesday’s strong to storm-force southerly winds have formed widespread snowdrift accumulations. Ridgelines and broad ridges have often been blown away. In the south, the fresh snow was additionally deposited on top of a weak Snow deposited on the ground in a multiplicity of layers.EAWS glossary. Fresh and drifted snow is often lying on an unfavourable old snow surface of Snow grains, solid, with multiple flat glassy faces and sharp edges. Developed from faceting metamorphism, usually poorly bonded to one another (fewer contact points), a critical factor in avalanches if a faceted layer is covered with bonded snow. Typical grain size: 0.5 to 3 mm See also: www.snowcrystals.itEAWS glossary or snow-covered 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 and is therefore still easily triggered.
In southern Valais, Ticino and Grisons, 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. The number of avalanches triggered by human activity has decreased over the course of the week, but many 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 still being reported. Snow deposited on the ground in a multiplicity of layers.EAWS glossary structure is somewhat more favourable on the northern flank of the Alps and in northern Valais, but there are weak layers deeper in the snowpack in these regions too. These may still be triggered, especially where there is little snow and at transitions from a deep to shallow snowpack.
Weather review for Wednesday
Conditions were often cloudy on Wednesday and a little snow fell in the south. There were brighter intervals in the afternoon in the west.
Fresh snow
From Monday evening to Wednesday evening, above approximately 1000 m:
- Main Alpine Ridge from the Simplon Pass to the Bernina region and south of there: 20 to 30 cm
- rest of the Main Alpine Ridge and rest of the Engadine: 5 to 15 cm; elsewhere less or dry.
Temperature
At midday at 2000 m, between -3°C in the north and -5°C in the south
Wind
From southerly directions:
- moderate to strong overnight
- subsiding during the day, mostly light in the afternoon
Weather forecast to Thursday
Overnight to Thursday, some snow will continue to fall in the south and east above approximately 1000 m. Conditions will be very sunny everywhere during the day, with clouds gathering from the south-west in the afternoon.
Fresh snow
A few centimetres on the central part of the Main Alpine Ridge and to the south and in central Grisons and the Engadine
Temperature
At midday at 2000 m, around -1°C
Wind
- Light to moderate from westerly directions
- Foehn winds will rise in the Alpine valleys of the north in the afternoon.
Outlook
Friday
Precipitation will set in from the west overnight to Friday. During the day, conditions will be very cloudy and there will be occasional precipitation, falling as snow above approximately 1300 m. Around 20 to 30 cm will fall in the extreme west of Lower Valais. There will be brighter intervals in the south during the day. The wind will increasingly become a moderate southwesterly.
Avalanche risk will increase in the west with the fresh snow, but will otherwise not change significantly.
Saturday
Precipitation will come to an end in the north overnight to Saturday. Conditions will be very sunny with light winds during the day.
Avalanche risk will decrease a little but only very slowly in southern Valais, Ticino and Grisons due to the distinct and 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.