Ticino Sopraceneri
Untere Maggiatäler
Avalanche Problems
New snow + Persistent weak layers
2+
Field notes
New snow
Easy to spot - the snow is fresh. Look at recent avalanche activity in similar terrain, and pay attention to how much new snow has fallen in the last three days. Critical loading depends on temperature, wind, and what was on the surface before the storm. SLF advises waiting until the Snow deposited on the ground in a multiplicity of layers.EAWS glossary has had time to bond before committing to steep terrain in fresh snow.
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
In westernmost and northern Lower Valais, there is somewhat more snow at high altitudes than is usual at this time of year. Elsewhere, snow depths are below average and in the south they are well below average. On south-facing slopes and generally below 2400 m, the Snow deposited on the ground in a multiplicity of layers.EAWS glossary is mostly wet or crusted.
On the Main Alpine Ridge and to the south of there, the last few days' fresh and drifted snow is lying at high altitudes on a thin but weak Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary 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.
North of the Main Alpine Ridge, there was little transportable snow so only small snowdrift accumulations have formed. However, where these are 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, they are still prone to triggering. In addition, in the inneralpine regions of Valais and throughout Grisons, there are some pronounced 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, especially on northern and eastern slopes above approximately 2400 m. However, hardly any avalanches have been triggered in these layers for some days.
Weather review for Thursday
Conditions were very cloudy in the south with a little snowfall above approximately 1600 m while they were sunny and mild in the inneralpine regions and in the north.
Fresh snow
Since Wednesday afternoon, 5 cm, and locally up to 10 cm, of snow have fallen on the Main Alpine Ridge from the Nufenen Pass to Bernina and south of there.
This means that, above approximately 2000 m, total snowfall since Tuesday has been:
- Valle Maggia: 30 cm
- rest of Ticino, Moesano, Bernina region: 15 to 20 cm
- rest of the Main Alpine Ridge: 5 to 15 cm
- elsewhere mainly dry
Temperature
At midday at 2000 m, between +3°C in the north and -1°C in the south
Wind
- Moderate from southerly directions
- In the afternoon, a foehn wind set in in the north
Weather forecast to Friday
Conditions will be sunny and clouds will gather in the west in the afternoon.
Fresh snow
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Temperature
At midday at 2000 m, between +3°C in the north and -1°C in the south
Wind
- Moderate southerly to southwesterly winds during the night in the north and at high altitudes, sometimes rising to strong in those regions exposed to the foehn wind
- Initially light winds during the day with moderate southwesterly winds in the afternoon in the west
Outlook to Sunday
On Saturday, there will be sunny intervals in the west and conditions will even be mainly sunny in the east. Temperatures will remain mild and winds will be light. A foehn wind will rise in the north on Sunday. In those northern and easternmost regions exposed to the foehn wind, conditions will be very sunny and mild, while they will be mainly cloudy, but substantially dry, elsewhere.
Avalanche risk will decrease, but only slowly, in Valais, Grisons and the south due to the weak Snow deposited on the ground in a multiplicity of layers.EAWS glossary structure.