Boletín de aludes

Pronounced persistent weak layers. Caution urged towards fresh snowdrifts

Pronounced persistent weak layers. Caution urged towards fresh snowdrifts

Pronounced weak layers inside the old snowpack can be triggered even by one sole skier, especially in Rätikon, Silvretta and Verwall on W/N/E-facing slopes. This applies especially to transitions from shallow to deep snow above 2000 m, e.g. entries into gullies and bowls. Also remote triggerings are possible in isolated cases. Triggered avalanches can easily grow to dangerously large size. The fresh snowdrift accumulations from Friday are often still prone to triggering. Due to fresh snow and wind, the snowdrift accumulations will continue to expand during the morning. Avalanches can be triggered by the weight of one person and reach medium size. In addition, the snowdrift accumulations formed at the beginning of the week are still prone to triggering in isolated cases on shady slopes above 1800 m. For winter sports enthusiasts the situation is critical, above all else the persistent weak layer is a threat, and very difficult to perceive/assess. In steep rocky terrain, small superficial loose-snow avalanches can release due to solar radiation and daytime warming. Glide-snow avalanches possible on steep grassy slopes.

Between Friday morning and Friday afternoon there was 10-15 cm of fresh snow registered in Bregenzerwald, Allgäu Alps and Tannberg, elsewhere up to 10 cm. Strong westerly winds transported the snow. In the latter part of the night, a strong easterly wind intensified in east-west passages, generating fresh, trigger-sensitive snowdrift accumulations. The new drifts were deposited frequently atop melt-freeze crusts on sunny slopes, on shady slopes atop settled powder, elsewhere above the treeline atop wind-pressed old snow: they are often prone to triggering. During the day the fresh wno on steep sunny slopes will become moist. Pronounced weak layers are evident at mid-level inside the snowpack. They are prone to triggering on W/N/E-facing slopes and very difficult to evaluate. Where these layers are covered over by thick fresher layer they are no longer a threat. In Rätikon and Verwall and Silvretta, the covering is shallower, thus they can be triggered, particularly in transition zones from shallow to deep snow.

Perfect winter weather, brilliant sunshine from morning til evening, not much wind. Temperature at 2000 m: -10 to -3 degrees. Winds will shift from easterly to southerly, blow at moderate strength at high altitude.

On Sunday it will remain sunny, accompanied by some cirrus cloud. Slight foehn influence, towards evening the SW wind will intensify somewhat. Avalanche danger is not expected to change significantly.