Prättigau and Davos
Südliches Prättigau
Day Risk Profile
Avalanche Problems
Persistent weak layers
2+
Field notes
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.
Wet snow
2
Field notes
Rolling snowballs, deep penetration when you step or ski, and small natural slides are clear signals that the Snow deposited on the ground in a multiplicity of layers.EAWS glossary is losing strength. After a clear, cold night the surface often freezes into a strong supporting Layer of hard-compacted snow resulting from a melt-freeze process or wind.EAWS glossary, and conditions are favourable in the early morning. After a warm, overcast night, the problem may be present from the start of the day. Plan early returns and watch the runout zones below you.
Snowpack & Weather
Snowpack
In the regions north of a line from the Rhône to the Rhine and in the extreme west of Lower Valais, 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 deposited on the ground in a multiplicity of layers.EAWS glossary are mostly thickly covered and are now hardly triggerable by human activity.
In the regions south of a line from the Rhône to the Rhine, the 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 that have been relevant since the beginning of January are still present. However, the number of avalanche-prone locations has decreased significantly. Danger signs have still been observed in the last few days, particularly in Grisons, and dry avalanches have been triggered in deeper layers of the Snow deposited on the ground in a multiplicity of layers.EAWS glossary.
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 lower part of the Snow deposited on the ground in a multiplicity of layers.EAWS glossary are being weakened as they become moistened for the first time. Wet The abrupt release of a slab of snow on a mountain slope. After crack initiation and crack propagation in a weak layer the released slab comprises 3 elements: The weak layer, the gliding horizon and the slab. If the slope angle is steep enough, the slab will glide down. If the slope is not steep enough, the slab will settle down on the failed weak layer. Possibly a whumpf sound will follow due to air pressed out of the weak layer. The fracture line will be sharp edged.EAWS glossary are possible as the day progresses. These can occur naturally but can also be occasionally triggered by winter sports participants, at present mainly on sunny slopes below approximately 2600 m. Isolated gliding avalanches are also possible here.
Weather review for Friday
Despite the Sahara dust, the night was mostly clear and the outgoing longwave radiation was quite good. It was rather sunny during the day. However, visibility was obscured by Sahara dust.
Fresh snow
-
Temperature
At midday at 2000 m, between +7 °C in the north and +3 °C in the south
Wind
Mainly light easterly winds, occasionally moderate in the north
Weather forecast to Saturday
The outgoing longwave radiation during the night will be mostly good. Conditions during the day will be quite sunny. However, there will be sometimes denser high cloud cover and visibility will be obscured by Sahara dust.
Fresh snow
-
Temperature
At midday at 2000 m, around +4 °C in the north and +1 °C in the south
Wind
Mainly light from the south to southeast
Outlook to Monday
The nights will be mostly clear in the north and partly cloudy on the southern flank of the Alps. During the day, it will be mostly sunny at high altitudes on both days. Visibility will be partly obscured by Sahara dust, particularly on Sunday. It will be partly cloudy in the Jura, along the Prealps and in the south. Isolated rain showers are possible, especially in the Jura. The zero-degree level will drop and will be around 2200 m in the north and 2000 m in the south. There will be mostly light south to southeasterly winds.
The danger of dry avalanches will continue to decrease, but only slowly in Grisons due to the weak Snow deposited on the ground in a multiplicity of layers.EAWS glossary structure. The danger of wet and gliding avalanches will increase somewhat during the course of each day. Touring and off-piste descents should be completed in good time.