Churfirsten and Rhine Valley
Appenzeller Alpen
Hard-to-read day. Moderate, with wind slab and gliding snow in play — part of it readable at the surface, part of it buried and silent.
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.
Gliding snow
1
Field notes
Almost impossible to predict precisely, even when the warning signs are visible. A crack visible on the snowpack surface formed by snow-gliding on steep, and particularly grass-covered slopes. Areas below slopes with visible glide cracks should be avoided whenever possible due to threat of gliding sluffs or avalanches.EAWS glossary — gaps that open in the Snow deposited on the ground in a multiplicity of layers.EAWS glossary down to the ground — are often precursors to release, but they don't tell you when. A glide avalanche can release minutes after the cracks appear, or weeks later, or not at all. Some release without any visible warning. Avoid lingering anywhere near glide cracks: above them, alongside them, or below in the runout.
Snowpack & Weather
Snowpack
On wind-protected shady slopes, the weekend’s fresh snow is lying on 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 in some places. Loose fresh snow is additionally being transported by strong winds from variable directions resulting in the formation of snowdrift accumulations that are prone to triggering. Further small-scale snowdrift accumulations will form in Wednesday's strong southerly winds.
In the inneralpine regions of Valais and Grisons, the layers of fresh and drifted snow are also lying on a weak Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary with pronounced 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. Avalanches can sometimes propagate into these deep weak layers or be triggered there directly in isolated cases. In other regions, weak layers in old near-ground Snow deposited on the ground in a multiplicity of layers.EAWS glossary still remain in places on shady slopes but are now mainly so thickly covered that they are largely insensitive to triggering.
Weather review for Tuesday
Overnight to Tuesday, there was broken cloud in the east with a little snow falling above 1200 m. Elsewhere the night was mainly clear. During the day, conditions were mainly sunny while the east became increasingly sunny once any remaining cloud had broken up.
Fresh snow
Central and eastern parts of the northern flank of the Alps, northern Grisons: 2 to 5 cm
Temperature
At midday at 2000 m, around +1 °C in the west and south and -4 °C in the east.
Wind
- At high altitudes, moderate to strong, mostly moderate from northerly directions during the day
- Moderate to strong northerly foehn wind in the Alpine valleys of the south overnight to Tuesday
- Moderate to strong bise wind in the Jura
Weather forecast to Wednesday
Skies will mainly be clear overnight to Wednesday with broken cloud over central and southern Ticino. Conditions will mainly be sunny during the day and increasingly sunny as the day progresses in the far south.
Fresh snow
-
Temperature
At midday at 2000 m, around 0 °C in the north and -2 °C in the south
Wind
- Mainly moderate northerly to northeasterly overnight to Wednesday
- Moderate to strong easterly to southeasterly during the day
- Moderate southerly foehn wind during the day in the upper foehn valleys of the north.
- Strong bise wind in the Jura
Outlook to Friday
After clear nights in the mountains, conditions will mainly be sunny on Thursday and Friday with broken cloud cover developing on Friday especially in the south. There will be a light to moderate northeasterly to easterly wind. The zero-degree level will be about 2000 m around midday on both days.
The danger of dry avalanches will decrease, but only slowly on shady slopes. With solar radiation and daytime warming, the danger of wet avalanches will increase somewhat on steep sunny slopes over the course of each day. Isolated gliding avalanches will be possible.