Prättigau and Davos
Südliches Prättigau
Hard-to-read day. Considerable, with new snow, persistent weak layers and wet snow in play — you can read the surface problem; the buried one sets the consequence.
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.
Wet snow
1
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
The sometimes large amounts of new snow and wind-drifted snow in the extreme west of Lower Valais, in the north, and in large parts of Grisons are in some cases still prone to triggering. In the other regions, more recent snowdrift accumulations are in some cases still prone to triggering, but are mostly smaller. In addition, avalanches can be triggered in the upper layers of the underlying Snow layers deposited from earlier precipitation, prior to fresh fallen snow. Old snow layers consist of metamorphosed snow crystals.EAWS glossary, especially on north- and east-facing slopes.
As a consequence of solar radiation, numerous loose snow avalanches are to be expected from the new fallen snow, especially in the regions exposed to heavier precipitation.
Weather review for Saturday
In the north and in Grisons, snow fell above approximately 1300 m, increasingly in the form of showers during the day. In Valais, conditions were changeable with extended bright spells. In the south, conditions were very sunny.
Fresh snow
From Friday afternoon to Saturday afternoon, the following amounts of fresh snow fell above approximately 2000 m:
- Northern Alpine ridge from the Wildstrubel to the St. Gallen Alps: 20 to 30 cm
- Rest of the northern flank of the Alps, Lower Valais, northern Grisons, Engadine, Val Müstair: 10 to 20 cm, less elsewhere
Over the three days from Wednesday evening to Saturday afternoon, altitudes above approximately 2000 m thus saw the following snowfall:
- Extreme west of Lower Valais, northern Alpine ridge excluding the Alpstein-Alvier area and Liechtenstein, as well as northern Grisons, Engadine, Val Bregaglia, Val Poschiavo, Val Müstair: mostly 30 to 50 cm, with up to 70 cm in places in the Areas above approximately 3000 m (particularly glaciated areas).EAWS glossary
- Rest of the northern flank of the Alps, rest of Lower Valais: 15 to 30 cm
- Less elsewhere, no snow in the far south
Temperature
At midday at 2000 m, between -3 °C in the north and +2 °C in the south
Wind
Moderate to strong along the central and eastern Main Alpine Ridge, otherwise light to moderate from northerly directions
Weather forecast to Sunday
After a mostly clear night, it will be quite sunny. As the day progresses, there will be cumulus clouds and an increasing amount of high-level cloud cover.
Fresh snow
-
Temperature
At midday at 2000 m, between 0 °C in the north and +3 °C in the south
Wind
Shifting to southwesterly and mostly light
Outlook to Tuesday
Sunday night into Monday will be partly clear in the east, and cloudy elsewhere. In the morning, there will still be bright spells in the east; elsewhere, it will be mostly cloudy with showers, especially along the northern flank of the Alps. The snowfall level will be just below 2000 m. On Tuesday, it will initially be sunny in the west after a mostly clear night. As the day progresses, clouds will gather. In the east, after a cloudy night, some residual cloud will remain in the morning. After that, there will be brighter intervals. Conditions will be very sunny in the south. On both days, the wind will blow from westerly directions and will remain moderate at times in the north on Monday, and light on Tuesday. The zero-degree level will be 2200 m in the north and 2500 m in the south, gradually rising a little as the day progresses on Tuesday.
The danger of dry avalanches will decrease, but only slowly on very steep north-facing slopes in the Areas above approximately 3000 m (particularly glaciated areas).EAWS glossary. Wet avalanches are to be expected in the near-surface layers on very steep terrain, particularly as a consequence of solar radiation.