Gotthard area
Uri Rot Stock
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
On the southern flank of the Alps and in Upper Engadine, this week's fresh and drifted snow has been deposited on a weak Snow deposited on the ground in a multiplicity of layers.EAWS glossary, resulting in numerous medium and even large naturally triggered avalanches and avalanches triggered by human activity. In these regions, avalanches can still be triggered very easily in the Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary in many areas, including remotely. Avalanches may also be triggered deeper in the snowpack in southern Valais and in the inneralpine regions of Grisons, especially on northern and eastern slopes.
The 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. In these regions too, there are 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 snowpack. These may still be triggered in some places, especially where there is little snow and at transitions from a deep to shallow snowpack.
Weather review for Friday
It was mostly cloudy in the north and west. Some snow fell at times above 800 m. In the late morning it was quite sunny in the east and south, then cloudy but mostly dry.
Fresh snow
- Western Jura, extreme west of Lower Valais, Vaud and Fribourg Alps: 5 to 10 cm
- elsewhere less or dry
Temperature
At midday at 2000 m, around -4 °C
Wind
In the west and north, moderate at times from the southwest, otherwise mostly light
Weather forecast to Saturday
After a partly clear night in the west, it will often be cloudy but dry. Otherwise it will be quite sunny, especially in the late morning, then increasingly cloudy.
Fresh snow
-
Temperature
At midday at 2000 m, around -4 °C
Wind
Mostly light from the south to southwest
Outlook to Sunday
On Sunday and Monday it will be quite sunny in the mountains with patches of cloud. On the southern flank of the Alps, it will be quite sunny on Sunday and mostly cloudy on Monday.
Winds will be mostly light, with occasionally moderate southwesterly winds in the northwest on Monday.
The avalanche danger will decrease, but only very slowly in the inneralpine regions and in the south due to the weak Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary. Avalanches triggered by human activity are still to be expected in these regions. Caution and restraint are required.