Gotthard area
Uri Rot Stock
Day Risk Profile
Avalanche Problems
Wind slab + Persistent weak layers
2=
Field notes
Wind slab
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.
Persistent weak layers
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 are very challenging to recognise. 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 and shooting cracks are typical when present, but you can have a serious weak layer with no warning signs at the surface. Knowledge of how the Snow deposited on the ground in a multiplicity of layers.EAWS glossary has evolved is essential. SLF's travel advice is direct: travel conservatively, avoid terrain where the consequences of being caught are large, and treat the history of weather and snow as more important than what you can see today. Read the full bulletin.
Snowpack & Weather
Snowpack
Snow deposited on the ground in a multiplicity of layers.EAWS glossary structure is unfavourable in many locations in southern Valais, Ticino and Grisons, with 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 that are prone to triggering in the middle and lower part of the snowpack. 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 and avalanches triggered by human activity, often remotely, continue to be reported from these regions. Snowpack 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 Monday
Conditions were very cloudy in the south, with light snowfall above approximately 1400 m. Elsewhere, there were sunny intervals in the mountains, with cloud thickening from the west.
Fresh snow
On the central part of the southern flank of the Alps a few centimetres above 1400 m
Temperature
At midday at 2000 m, around -3°C
Wind
Moderate southeasterly winds at times on the Northern Alpine Ridge, otherwise mostly light
Weather forecast to Tuesday
In the north, conditions will range from cloudy with bright intervals to very cloudy, with the brighter intervals primarily occurring in the Visp valleys and Grisons. In the south, conditions will be very cloudy. Some precipitation is expected, especially in the west and south. The snowfall level will be between 1000 and 1500 m.
Fresh snow
- Jura, extreme west of Lower Valais, northern Valais, central part of the southern flank of the Alps: 5 to 15 cm
- otherwise a few centimetres, dry in central Grisons and the Engadine
Temperature
At midday at 2000 m, between -2°C in the north and -5°C in the south
Wind
Increasingly moderate southwesterly, strong in the west
Outlook for Wednesday and Thursday
On the southern flank of the Alps, both days will see cloudy skies with bright intervals and some precipitation. In the north, conditions will be very cloudy, with repeated precipitation, which will be centred in particular in the west and on the northern flank of the Alps. More than a metre of fresh snow is expected in westernmost and northern Lower Valais, otherwise 70 to 100 cm on the northern flank of the Alps west of the Reuss and in Lower Valais, 40 to 70 cm on the northern flank of the Alps east of the Reuss and in Upper Valais, elsewhere less. The snowfall level will drop from 1800 m to 1200 m in the north and will be at 1300 m in the south. The wind will often be strong to storm-force from westerly directions. Avalanche risk will increase rapidly and significantly to level 4 (high) on Wednesday in many areas on the western part of the northern flank of the Alps and in Valais. Avalanche risk will increase in other regions too, most notably on the rest of the northern flank of the Alps, in the Gotthard region and in northern Grisons.