Central Prealps
Melchtal
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
In the west and north, layers of fresh and drifted snow from the last two days are lying on the thick layers of fresh snow from the past week, which are increasingly consolidating. Below this, in these regions the central section of the Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary contains 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 places. Avalanches triggered in near-surface layers can sometimes take these deeper layers of old snowpack with them and can become very large at times. This applies in particular to the northern Alpine ridge.
In Ticino, Grisons and some regions of southern Valais, the layers of new and drifted snow from the past week are thinner than they are further north. They are lying on an unstable Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary with 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. In these regions, human activity can still trigger avalanches very easily in the old snowpack, even from great distances. Avalanches may currently also be triggered in the treeline area or in sparse forest.
Gliding avalanches are increasingly possible on steep grassy slopes below approximately 1800 m.
Weather review for Friday
It was overcast in the north. On Friday, it snowed until the early hours of the morning in particular, and especially on the northern flank of the Alps. The snowfall level was around 1000 m, and around 700 m on the eastern part of the northern flank of the Alps. In the south, it cleared up during the night and was quite sunny during the day.
Fresh snow
From Thursday afternoon to midday on Friday, above approximately 1200 m:
- Vaud Alps, northern Lower Valais: 30 to 50 cm
- Rest of Lower Valais, rest of the northern flank of the Alps, not including the Prealps, northern Prättigau, Silvretta, Samnaun: 20 to 40 cm
- Otherwise less, largely dry south of the Main Alpine Ridge
Temperature
At midday at 2000 m, between -4 °C in the north and +1 °C in the south
Wind
From the northwest
- Increasing during the night
- Strong to stormy during the day on the Main Alpine Ridge and on the northern Alpine ridge
- elsewhere mostly moderate at high altitudes
Weather forecast to Saturday
It will be very cloudy north of the Main Alpine Ridge. It will continue to snow. During the night there will be only light snowfall, mainly in the east. During the day, snowfall will be widespread, and intense on the central and eastern parts of the northern flank of the Alps and in northern Grisons. Conditions will be mostly sunny south of the Main Alpine Ridge.
Fresh snow
The snowfall level will rise from 1000 to 1600 m. The following amounts of fresh snow are expected from Friday afternoon to Saturday afternoon:
- Northern Alpine ridge from the Aletsch region to the Alpstein region, northern Grisons: 20 to 40 cm
- Rest of northern flank of the Alps, rest of Valais, central Grisons: 10 to 20 cm
- elsewhere less; mostly dry on the southern flank of the Alps
Temperature
Rising, at midday at 2000 m between -2 °C in the north and +2 °C in the south
Wind
Northwesterly wind, increasing again
- Strong to stormy during the day on the northern Alpine ridge and Main Alpine Ridge
- otherwise moderate to strong at altitude
- Mostly moderate northerly winds on the southern flank of the Alps down into the upper valleys
Outlook to Monday
On Sunday, it will be mostly sunny with denser clouds at times in the Jura, on the northern flank of the Alps and in northern Grisons. Winds will be light to moderate from westerly directions. On Monday, it will be mostly sunny on the southern flank of the Alps and in Valais. Otherwise, it will be generally very cloudy and some precipitation is possible, especially towards the east. The snowfall level will be around 1500 m. It will be appreciably warmer, especially in the south with +5 °C at midday at 2000 m. The avalanche danger will decrease, especially in western and northern regions with a lot of snow. Isolated naturally triggered avalanches are still possible on Sunday, especially on the central and eastern parts of the northern flank of the Alps and in northern Grisons. In southern Valais, northern Ticino and Grisons, the avalanche danger will decrease more slowly. Conditions for touring and off-piste skiing remain critical in many places here.