Bollettino valanghe

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 southerly foehn wind is generating easily triggered snowdrift accumulations, even by the weight of one sole skier and possibly reaching medium size. For winter sports enthusiasts the situation is critical, above all else the persistent weak layer is a threat, and very difficult to perceive/assess. Defensive route selection is called for. In steep rocky terrain, small superficial loose-snow avalanches can release due to solar radiation and daytime warming. Generally small glide-snow avalanches possible on steep grassy slopes.

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. Avalanches can fracture down to deeper layers and then grow to large size. As a result of strong foehn wind, fresh trigger-sensitive snowdrifts will be generated on shady slopes in particular. At high altitudes the snowpack surface shows heavy effects of wind, only on shady slopes and in wind-protected terrain is the snow still loose. During the course of the day the melt freeze crust will soften on sunny slopes. On crests are often powerful, leaning cornices which require attentiveness.

Sunshine again, little wind, the beautiful weather will persist into the afternoon, then clouds will gradually move in above summit level, the southerly winds intensify by evening. During the night, snowfall and a cold front, the wind will shift from southerly to northwesterly. Temperature at 2000 m: -6 to 0 degrees. Noticeably dropping temperatures On Monday night. Moderate southerly winds at high altitudes.

Monday night, snowfall will set in above 800 m. Tuesday morning, persistent snowfall. Moderate to brisk NW winds will be blowing. Avalanche danger will increase widespread.