Bulletin d’avalanche

Fresh, covered snowdrifts, weak old snow: both prone to triggering

Fresh, covered snowdrifts, weak old snow: both prone to triggering

In wind-impacted steep terrain, fresh and older (now covered) snowdrift accumulations can be triggered even by one sole winter sports enthusiast. Particularly on high-altitude shady steep slopes the snowpack can fracture down to deeper layers. These red flags are not visible to the naked eye. Whumpf noises and glide cracks are alarm signals. Slab avalanches are then possible to trigger by large additional loading. On steep grass-covered slopes more than anywhere else, isolated small-to-medium glide snow avalanches are possible.

Monday was mostly dry. Last night there was 5-10 cm of fresh snow registered, accompanied by intermittently strong winds; in the Bregenzerwald mountains and towards Kleinwalsertal as much as 20 cm. Fresh snow and newly generated snowdrift accumulations were deposited on a consolidated, often rain-encrusted and settled old snowpack up to 1800 m. With ascending altitude exposed zones had freshly deposited and loosely-packed old snow transported by intermittently strong-to-stormy winds (predominantly W/NW) over the last few days. Thus, in ridgeline and pass areas and behind abrupt changes in the landscape, snowdrifts repeatedly accumulated. These are now blanketed, making them difficult to recognize and frequently prone to triggering. At mid-level in the snowpack on high-altitude shady slopes there are layers of faceted crystals evident.

At the start of the day widespread snowfall is expected, later in the morning it will lessen to snow showers. This afternoon it will be dry, the clouds will disperse. Temperature at 2000 m: -8 degrees. High altitude northwesterly winds will initially be strong, slacken off during the course of the day.

On Tuesday night and during the day on Wednesday, further precipitation is anticipated. It will remain cold. Avalanche danger levels will increase due to fresh snow and new snowdrift accumulations. Andreas Pecl