Churfirsten and Rhine Valley
Appenzeller Alpen
Stable day. Low, with only wind slab named — visible where it sits, and easy to go round.
Day Risk Profile
Avalanche Problems
Wind slab
1
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
The number of places where avalanches can be triggered in near-surface snow layers has decreased. Isolated avalanches are repeatedly being triggered in near-ground 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 in the inneralpine and southern parts of Grisons, and these may still become large. In other regions, although there are still weak layers 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 on shady slopes, they are mostly so thickly covered that they are very unlikely to be triggered.
With the storm-force westerly to northwesterly wind, at first any old snow that is still loose will be transported and, once snowfall has set in, the fresh snow will also be transported to a great extent. New and drifted snow will be deposited on various surfaces, some of which are unfavourable: on north-facing slopes, especially in sheltered locations, onto snow which is still very loose, whereas up to high altitudes on south-facing slopes often onto a Layer of hard-compacted snow resulting from a melt-freeze process or wind.EAWS glossary. In many cases, the surface of the Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary has also been profiled by the wind and is irregular.
Weather review for Tuesday
After a mainly clear night, Tuesday saw mostly sunny conditions.
Fresh snow
-
Temperature
At midday at 2000 m, around 0 °C in general and around -3 °C in eastern Grisons
Wind
Northerly:
- often moderate at high altitudes in the morning
- otherwise light
Weather forecast to Wednesday
After a partly clear night into Wednesday, cloud cover will increase from the west in the morning. Conditions will remain very sunny into the afternoon in the east and south in particular. In the west and north, precipitation will set in during the afternoon.
Fresh snow
The snowfall level on the northern flank of the Alps will fall rapidly from around 1400 m to around 1000 m. By Wednesday afternoon the following amounts of snow will have fallen above 1500 m:
- westernmost Lower Valais and the northern flank of the Alps: 5 to 15 cm
- rest of Lower Valais and Prättigau: around 5 cm
- further south: less or mostly dry
Temperature
- Falling noticeably as the day progresses
- At midday at 2000 m, between -3 °C in the north and +2 °C in the south and in Grisons
Wind
- Overnight still mainly light southwesterly
- From early morning in the west and north, increasing significantly to strong to storm-force westerly to northwesterly
- In the south and in Grisons, increasing to moderate to strong westerly at high altitudes over the course of the day
Outlook
Thursday
Overnight to Thursday and during the day, there will be widespread snowfall down to low altitudes in the north, and this will be persistent especially in Lower Valais and on the northern flank of the Alps. In these areas, by late afternoon 40 to 60 cm of snow will have fallen at high altitudes. The heaviest precipitation is expected during the night to Thursday. In the mountains, the precipitation will be accompanied by storm-force northwesterly winds. In central Ticino and Sotto Ceneri, conditions will be very sunny with a strong northerly foehn wind. Avalanche danger will increase generally, and significantly so in Lower Valais, on the northern flank of the Alps and in northern Grisons.
Friday
Snow will continue to fall overnight to Friday. As the day progresses, the snowfall will end and bright spells will spread increasingly from west to east. The southern flank of the Alps will be sunny. The northwesterly wind will start to ease slightly only as the day progresses. Temperatures will remain wintry, with the north seeing midday temperatures of -12 °C and the south -5 °C. Avalanche danger may continue to increase somewhat, especially on the northern flank of the Alps.