Bollettino valanghe

Snowdrift problem above 2300 m. Below 2200 m, daytime wet-snow+glide-snow avalanches

Snowdrift problem above 2300 m. Below 2200 m, daytime wet-snow+glide-snow avalanches

New snow and fresh and older snowdrift accumulations are prone to triggering above 2300m, can be triggered even by minimum additional loading and unleash dangerously large-sized avalanches. Avalanche prone locations are found in steep terrain in all aspects, behind protruberances and in wind-loaded gullies and bowls. Spread and frequency of danger zones increase with ascending altitude. If avalanches fracture down to deeper layers of the snowpack they can grow to dangerously large size. Below 2200 m wet-snow avalanches can trigger naturally due to warmth and solar radiation or be triggered by winter sports enthusiasts. On steep south-facing slopes, wet slides and avalanches can release even at high altitudes. Furthermore, glide-snow avalanches can occur at any time of day or night. Caution on slopes where there are glide cracks.

The intensive persistent rainfall up to 2200 m weakened the snowpack as it became thoroughly wet. Following a night of nearly clear skies, a melt-freeze crust formed which will swiftly soften during the day (solar radiation, zero-degree level at 3300m). The rain and mild temperatures have helped the snowpack to quickly settle. At high altitudes where there was no rain (above 2300m) the snowpack is stabilizing more slowly. Through stormy W/NW winds the snow was intensively transported on both days, new snowdrift accumulations formed also distant from ridgelines. Brisk to strong W/NW winds have generated snowdrift accumulations at high and high-alpine altitudes which are prone to triggering. The transported snow was deposited on wind crusts, melt-freeze crusts or atop older snowdrifts, on high altitude shady slopes also on loose, powdery layers, making it prone to triggering. On south-facing slopes, bonding to the old snowpack is better. In addition, on very steep high-altitude shady slopes there are weak layers at mid-level inside the snowpack in some places: they are prone to triggering.

A high-pressure front determines weather conditions today. Following a night of nearly clear skies, today will be cloudless. Sunshine will dominate, wind still present, extremely mild (zero-degree level at 3300 m). Temperature at 2000 m: +8 degrees! Brisk to strong W/NW winds at high altitude.

The sequence of daytime warming and nighttime outgoing radiation has helped stabilize the snowpack. At high altitudes the snowpack is also settling, avalanche danger is receding.