Central Grisons and Anterior Rhine
Albulatal
Hard-to-read day. Considerable, with wind slab, persistent weak layers and gliding snow in play — you can read the surface problem; the buried one sets the consequence.
Day Risk Profile
Avalanche Problems
Wind slab + Persistent weak layers
3-
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.
Gliding snow
2
Field notes
Almost impossible to predict precisely, even when the warning signs are visible. A crack visible on the snowpack surface formed by snow-gliding on steep, and particularly grass-covered slopes. Areas below slopes with visible glide cracks should be avoided whenever possible due to threat of gliding sluffs or avalanches.EAWS glossary — gaps that open in the Snow deposited on the ground in a multiplicity of layers.EAWS glossary down to the ground — are often precursors to release, but they don't tell you when. A glide avalanche can release minutes after the cracks appear, or weeks later, or not at all. Some release without any visible warning. Avoid lingering anywhere near glide cracks: above them, alongside them, or below in the runout.
Snowpack & Weather
Snowpack
Especially on shady slopes, the large amounts of fresh and drifted snow from the last period of precipitation are lying on faceted 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. Avalanches can still be triggered in these weak layers in isolated cases, especially in areas with relatively little snow. These may be large.
In the inneralpine regions of Valais and especially Grisons, 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 middle of the Snow deposited on the ground in a multiplicity of layers.EAWS glossary are additionally still prone to triggering in some places, with avalanches possibly being triggered in near-ground weak layers in isolated cases.
With rising temperatures and a cloudy night in the north, gliding avalanche activity will continue to increase, initially especially below approximately 2200 m on the northern flank of the Alps.
Weather review for Friday
During the night into Friday, it was mostly very cloudy on the eastern part of the northern flank of the Alps and in northern and central Grisons. It was mostly clear in Valais, otherwise partly clear. Conditions were mostly sunny during the day.
Fresh snow
-
Temperature
At midday at 2000 m, between -3 °C in the north and +4 °C in the south
Wind
During the night into Friday, still moderate to strong from the northeast, during the day mostly moderate at high altitudes
Weather forecast to Saturday
During the night into Saturday, it will be partly clear on the southern flank of the Alps, otherwise mostly very cloudy. A little precipitation is expected during the night, especially on the northern Alpine ridge and in northern and central Grisons. The snowfall level will rise from 1400 to 1800 m. As the day progresses, sunny spells will increase from the southwest. In the west and on the southern flank of the Alps, it will be mostly sunny; there will be increasing bright spells in the east.
Fresh snow
- On the northern Alpine ridge and in northern and central Grisons: a few centimetres above 2000 m
- elsewhere less or dry
Temperature
Significantly increasing, at midday at 2000 m between +3 °C in the north and +6 °C in the south
Wind
- Moderate northerly winds initially on the northern Alpine ridge, the Main Alpine Ridge and the southern flank of the Alps; easing as the day progresses
- Elsewhere light
Outlook to Monday
The night into Sunday will be mostly clear. It will be sunny during the day. The night into Monday will be mostly very cloudy and showers are expected in the east. The snowfall level will be around 2200 m. It will be mostly sunny during the day. Winds will be light to moderate from westerly directions. It will be very mild and the zero-degree level will be just under 3000 m.
The danger of dry avalanches will continue to decrease. The danger of wet and gliding avalanches will increase on Sunday as the day progresses after a mostly clear night. On Monday it is likely to increase in the early morning due to the cloudy night and mild weather.