Persistent weak layers· Mattina
- Above 2,500 m
Naturally triggered avalanches expected during course of day
Rapidly rising wet-snow avalanche danger during course of day
During the course of the day, danger of wet-snow avalanches will increase. Isolated wet slab avalanches can be triggered by winter sports enthusiasts. After the melt-freeze crust (capable of bearing loads) softens iup, also naturally triggered wet-snow avalanches are possible. Caution urged particularly towards steep shady slopes at 2200-2500m which have not yet discharged and slopes in all aspects where there is area-wide snow on the ground. Avalanches can fracture in weak old snowpack layers, in isolated cases grow to large size and lay back huge runout zones, quite atypically. Backcountry tours and ascents to refuges need to be launched early in the day and brought to an end early.
During the night, a melt-freeze crust will form which is capable of bearing loads, then soften up during the daytime. At altitudes of 1800-2500m the ground-level layer of rotten snow is thoroughly wet even on north-facing slopes and is prone to triggering. On shady, steep high-altitude slopes there are unfavorable intermediate layers in the uppermost metre of the snowpack which can be triggering in some places. A deep mid-level section of compact layers blankets a fundament of buried hoar and faceted crystals.
On Friday, quite sunny weather will prevail from the start, with some high-altitude cirrus clouds and daytime convective cloud build-up. Tendency towards showers will be low. Still light winds in the mountains, the zero-degree level just below 3000m. Temperature at 2000m: up to +7 degrees; at 3000m: -1 degree. Light to moderate westerly-to-northwesterly winds at high altitudes.
Nocturnal outgoing radiation will be good. Conditions during the morning hours will be good. During the daytime, danger of wet-snow avalanches will increase.
Bulletin data: Avalanche Warning Service Vorarlberg (CC BY 4.0)