Western Prealps
Vallée de Joux
Avalanche Problems
No distinct problem
1
Field notes
SLF uses this label when no single problem dominates the assessment, often on lower-danger days. It doesn't mean conditions are safe: any avalanche type is still possible, and normal caution applies. On stable days this is usually a signal to enjoy the mountains with general awareness; on less-stable days where the assessment is still inconclusive, it's a signal to be cautious specifically because there's no clear pattern to follow.
Snowpack & Weather
Snowpack
After this week's snowfall, the snow depths in the north and west are well above average for the time of year. Deeper in the Snow deposited on the ground in a multiplicity of layers.EAWS glossary, especially on shady slopes above approximately 2400 m and in the Areas above approximately 3000 m (particularly glaciated areas).EAWS glossary in general, there are 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 in which avalanches, some large, have been triggered in recent days. In the regions exposed to heavier precipitation in the west and north, these weak layers are now thickly overlaid and are therefore no longer so easily triggered by winter sports participants. However, any avalanches may still become large. In areas with less fresh snow, avalanches are easier to trigger in these weak layers, but will not be quite as large.
With the north to northeasterly wind, snowdrift accumulations formed at high altitudes on Thursday.
Weather review for Thursday
A four-day period of precipitation, which brought a lot of fresh snow to the north and most especially the west, ended during the night to Thursday, with Thursday being mostly sunny in the mountains.
Fresh snow
Since Wednesday afternoon, 5 to 10 cm of snow has fallen in the north down to low altitudes. From Sunday evening until during the night to Thursday, the following amounts of fresh snow had thus fallen above approximately 1800 m:
- northern flank of the Alps, northern and extreme west of Lower Valais: 70 to 110 cm, with up to 150 cm in the far west
- rest of Lower Valais, northern Upper Valais, northern and central Grisons, Jura: 30 to 60 cm
- elsewhere: 10 to 30 cm
Temperature
At midday at 2000 m, around -5 °C in the north and -2 °C in the south
Wind
Moderate, locally strong north-northeasterly
Weather forecast to Friday
Conditions will be mostly sunny in the mountains.
Fresh snow
-
Temperature
At midday at 2000 m, around 0 °C
Wind
The northeasterly wind will die down during the night and will be mostly light during the day.
Outlook
Saturday
In the north, a few centimetres of snow will fall above around 1500 m during the night to Saturday. Saturday will be dry with relatively long bright intervals. Conditions will be very sunny in the south.
Avalanche risk will continue to decrease in the west and north. There will be no significant change in the south.
Sunday
Conditions will be very cloudy and some snow will fall in the west and north above around 1200 m, with 10 to 20 cm mostly in the far west. Winds will be moderate from the southwest, then from the west.
The risk of dry avalanches will increase slightly in the far west, otherwise it will not change significantly.