Goldberg Group Central

Foehn-induced snowdrifts triggerable, could fracture to deeper layers

Foehn-induced snowdrifts triggerable, could fracture to deeper layers

Avalanche danger above 2000 m is CONSIDERABLE, below that altitude danger is LOW. Main problem: snowdrift threat – the fresh foehn-induced drifts are highly varied with differing effects from valley to valley. Some are small and thin, often wide-ranging on freshly loaded slopes. The impulse of one persons is enough to trigger an avalanche (small-to-large). Experience is imperative. Danger zones are easily recognized. Second problem: persistent weak layer –hardly detectable from the snowpack surface. Potential weak layers inside the snowpack are likeliest in transitions into wind-loaded zones (often where snow is shallow). All in all the terrain has few spots where large additional loading (a fall, a group without distances, stomping) can trigger a slab avalanche. But if a slab triggers it can grow to large size.

The fresh snow from Friday (5-10 cm) was transported on Saturday in the Tauern and exposed zones of the Northern Alps. Small snowdrift masses were generated, currently not very prone to triggering. Beneath the fresh snow are compact layers which distribute the dynamic forces well. Inside the old snowpack, particularly on north-facing slopes, are faceted crystals which tend towards fracture propagation.

Monday will bring clear skies, outstanding mountain weather with but a few cirrus clouds in the morning. Winds will be light to moderate. Temperatures will rise. At 2000 m: 0 degrees. On Tuesday, heavy cloud cover will move in, visibility will be impaired swiftly. Fresh snow in 24 hours: 10-20 cm. Winds will shift to northwesterly, reach 30-40 km/hr. At 2000 m: -5 degrees.

As a result of fresh snow and wind, the situation is changing. Fresh snow problem. Danger Level: CONSIDERABLE (3). Caution: the new loading and superficial avalacnhes can fracture down to deeper layers in the snowpack and grow to large size.