Avalanche forecast

Heed fresh snowdrifts and weak layers in old snow

Heed fresh snowdrifts and weak layers in old snow

The snowdrift accumulations generated over the last few days are prone to triggering and can be triggered even by the weight of one single skier. The fresh snow blankets these drifts, making them difficult to recognize. Danger zones lie especially above 1800m on steep shady slopes, in ridgeline areas, behind protruberances, in gullies and bowls. Older weak layers in the old snow can easily trigger in places on W/N/E facing slopes, particularly in Rätikon, Silvretta and Verwall regions, especially above 2000 m in rarely-frequented terrain in transitions from shallow to deep snow, e.g. intries into gullies and bowls. Triggered avalanches can grow to dangerously large size. Backcountry skiing and freeriding tours demand defensive route selection. Due to warmth and rainfall, increasingly frequent naturally triggered avalanches and glide-snow slides can be expected during the course of the day.

Yesterday there was up to 15 cm of fresh snow registered, amid strong W/NW winds. The snow was transported, deposited atop trigger-sensitive weak layers, often atop breakable melt-freeze crustss, on north-facing slopes atop cold powder. Weak layers occur also at mid-level inside the snowpack and are prone to triggering on W/N/E facing slopes. They are undetectable! In Rätikon, Verwall and Silvretta the covering of this layer is shallower, thus easier to trigger. Danger zones are found where the snow is shallow in transitions from shallow to deep snow especially in unfrequented terrain. In addition, superficially triggering avalanches can fracture down to deeper layers and make the avalanches far large.

Fog will veil the peaks until midday, then light snowfall will set in, gaining in intensity through the afternoon. Initially the snow will fall above 1300 m, by evening the snowfall level will ascend to nearly 1800m. The amounts of fresh snow expected: moderate. Very windy in ridge areas. Temperature at 2000m: -5 to 0 degrees. Strong to stormy westerly winds at high altitudes.

Thursday will bring storm-strength, often gale-strength winds. The snowfall level will descend from 1900 m to nearly 1400m by evening. Due to snow transport, avalanche danger levels will increase at high altitudes.