Bollettino valanghe

Fresh snowdrift accumulations and weak layers: caution

Fresh snowdrift accumulations and weak layers: caution

Due to yesterday’s southerly foehn wind, snowdrifts accumulated which are easy to trigger. The new snow will be transported by increasingly strong W/NW winds deposited on top of them, and new trigger-sensitive snowdrift accumulations will be generated. Avalanches can be triggered by one sole skier and reach medium size. Danger zones lie especially on steep shady slopes, ridge areas, behind protruberances, in gullies and bowls. Weak layers in the old snow, particularly in Rätikon, Silvretta and Verwall on W/N/E facing slopes can often be triggered by one sole skier, especially above 2000 m in less frequent terrain in transitions from shallow to deep snow, e.g. at entries into gullies and bowls. Triggered avalanches can reach large size. Backcountry skiing and freeriding tours require defensive route selection.

Yesterday the last snowfall was transported by strong-to-stormy southerly foehn winds, generating new trigger-sensitive snowdrift accumulations. Last night it began to snow (10 cm) and during the day another 10 cm will be added to it, transported by increasingly strong W/NW winds, generating new trigger-sensitive snowdrift accumulations. Weak layers at mid-level inside the snowpack are evident on W/N/E facing slopes - they are difficult to detect and assess. In the Rätikon, Silvretta and Verwall the blanketing of this layer is shallower, and thus, easier to trigger. Avalanche prone locations are found in shallow-snow zones and in transitions from shallow to deep snow, particularly in less frequented terrain. In addition, triggered superficial avalanches can fracture down to more deeply embedded layers and grow to much larger size.

A low-pressure front is bringing cold wintery weather and moderate snowfall, persistent this morning but with only minor amounts. This afternoon the snowfall will slacken off, come to a gradual end, but visibility will remain reduced. Nighttime skies will be dry. Temperature at 2000 m: -5 degrees. Moderate to brisk W/NW winds at high altitudes.

Starting Wednesday afternoon, light snowfall will set in, intensifying somewhat through the afternoon, initially above 1300m, by evening the snowfall level will ascend to nearly 1800m. Storm-strength westerly winds. Avalanche danger will increase widespread during the course of the day. Due to rainfall, increasingly frequent naturally triggered avalanches can be expected.