Upper Engadine and Silvretta
Östliche Silvretta
Day Risk Profile
Avalanche Problems
New snow + Persistent weak layers
3-
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
South of a line Rhône - Rhine, the fresh snow from the weekend is 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. In these regions, avalanches may be triggered in deep 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 addition, the fresh snow is being transported by the strong northerly wind and forming snowdrift accumulations that are prone to triggering. Avalanches are also expected to be triggered within the fresh and drifted snow, especially in the regions in the south that have seen heavy snowfall.
North of a line Rhône - Rhine, the 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 Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary are mostly thickly covered and may only be triggered in isolated cases. The main danger in these regions comes from the fresh and drifted snow from the weekend, which is lying partly 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 on wind-protected shady slopes.
Weather review for Sunday
It snowed widely during the night, and very heavily in the south. During the day, there was still some precipitation in the south, otherwise it was partly sunny. The snowfall level was at low altitudes in the north and between 800 m and 1200 m in the south.
Fresh snow
From Saturday afternoon to Sunday afternoon above 1000 m in the north and 1500 m in the south:
- Main Alpine Ridge from the Monte Rosa region to Obergoms, western Ticino: 60 to 80 cm
- Adjacent to the north, remaining central part of the southern flank of the Alps, Main Alpine Ridge from the Rheinwald region to the Bernina Pass, central Grisons, Upper Engadine: 30 to 60 cm
- Elsewhere, a widespread 15 to 30 cm, and a few centimetres in the Jura
In total, the following amounts of snow have fallen since the onset of precipitation on Friday evening:
- Main Alpine Ridge from the Monte Rosa region to Bedretto, western Ticino: 80 to 120 cm
- Rest of the Main Alpine Ridge from the Grand St. Bernard to the Bernina Pass: 50 to 70 cm
- On the western and central parts of the northern flank of the Alps, not including the Prealps: 30 to 50 cm
- Elsewhere, a widespread 15 to 30 cm, and a few centimetres in the Jura
Temperature
At midday at 2000 m, between -6 °C in the north and -2 °C in the south
Wind
- Moderate to strong northerly wind during the night
- Moderate southerly wind during the day, at times strong to stormy on the northern flank of the Alps
Weather forecast to Monday
There will be a little precipitation during the night into Monday, especially in the south. The snowfall level will be around 1500 m. During the day, it will be mostly sunny in the south and partly sunny in the north.
Fresh snow
A few centimetres in the south
Temperature
At midday at 2000 m, between -2 °C in the north and +2 °C in the south
Wind
- Mostly light winds during the night
- During the day, there will be increasingly strong northwesterly winds in the south and generally at high altitudes, and a strong northerly foehn wind in the Alpine valleys of the south
Outlook to Wednesday
The night into Tuesday will be partly cloudy in the north, otherwise clear. It will be mostly sunny on Tuesday and Wednesday. There will be strong northerly winds at high altitudes on Tuesday. During the night into Wednesday, the northerly wind will ease and shift to the east. Subsequently, there will be moderate to strong Bise winds in the Jura and the western Prealps.
The danger of dry avalanches will decrease in many places, but only slowly in some regions due to the sometimes strong winds. With the solar radiation and the daytime warming, the danger of wet avalanches will increase somewhat over the course of each day.