Boletín de aludes

Treacherous persistent weak layer. Snowdrifts still prone to triggering on shady slopes

Treacherous persistent weak layer. Snowdrifts still prone to triggering on shady slopes

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. Triggered avalanches can easily grow to dangerously large size. The deep snowdrift accumulations formed at the beginning of the week are often still prone to triggering. Avalanches can be triggered by the weight of one person and reach medium size. For winter sports enthusiasts the situation is critical, demands a defensive route selection. Due to solar radiation and daytime warming, glide-snow avalanches and small-to-medium superficial loose-snow avalanches are possible during the course of the day, particularly on steep sunny slopes.

As a result of higher daytime temperatures and solar radiation, the deep snowdrifts from the beginning of the week were able to settle and consolidate particularly on sunny slopes; on shady slopes they still remain prone to triggering. On sunny slopes the uppermost layers became moist up to high altitudes again yesterday, overnight they form a breakable melt-freeze crust. Pronounced weak layers at mid-level inside the snowpack are evident. They are prone to trigger on W/N/E-facing slopes and difficult to evaluate. Where these weak layers are heavily covered, they are no longer dangerous. In Rätikon, Verwall and Silvretta the covering is shallower and thus, easier to trigger, particularly in transition zones from shallow to deep snow.

Pleasant weather still prevails, although it is windy. Sunshine dominates, even with some clouds high above summit level. Temperatures will drop somewhat, the zero-degree level at midday will be at 2000 m. Temperature at 2000 m: from +2 to -1 degree. Brisk to strong W/SW winds at high altitudes.

Frequent snowfall on Friday morning, heaviest in Bregenzerwald and Arlberg. Strong westerly winds will be blowing. Avalanche danger will increase somewhat from region to region.