Lower Tauern Central

AVOID foehn-induced snowdrifts from the weekend

AVOID foehn-induced snowdrifts from the weekend

Due to foehn-induced snowdrifts, avalanches danger is MODERATE.Snowdrift problem: wherever the foehn was blowing (wind signs are easily recognizable) there are on shady leeward slopes easily triggered snowdrift accumulations. The impulst of one sole persons can trigger avalanches, also small remote triggerings are possible. Potential avalanches are generally small, but the risk of being swept along and forced to fall need consideration, and in isolate cases there is enough snow to bury a person. Persistent weak layer: very few danger zones, mostly in shallow-snow transitions in shady, steep terrain, where large additional loading can trigger a rare slab and grow to medium size. Most danger zones are in NW/N/NE aspects in terrain distant from ridges and in steep gullies. Naturally triggered avalanches, due to sunshine and daytime warming: in very isolated cases, glide-snow avalanches can release. As of midday, small moist-snow slides are possible (danger of falling). Both types on extremely steep slopes.

The foehn wind of the last two days has change the situation somewhat, even though it is not easily recognizable. In leeward terrain (north-facing slopes and bowls) there are varyingly deep snowdrifts, often hardened, but easily triggered because the layers were deposited atop surface hoar and faceted crystals. Size and depth are modest. The most easily triggered layers are 10-20 cm thick. Apart from wind-impact on shady slopes there is stable powder atop a compact old snowpack, On sunny slopews the melt-freeze crust can bear loads in the right aspect and gradient (S/SW, 1500-2200m) and softens up to varying degrees during the daytime. Mostly, the uppermost 5-10 cm soften. Inside the old snowpack are faceted, soft layers (persistent weak layer), but these are currently unlikely to trigger.

Monday will bring high-altitude cloudbanks, otherwise sunny, pleasant backcountry touring weather conditions. Light winds. At 2000 m: -1 degree; at 3000 m: -5 degrees. Tuesday will have diffuse light conditions, compact high-altitude cloud cover will dominate, sunshine will be impeded. Winds light. At 2000 m: +5 degrees; at 3000 m: -4 degrees.

No significant change is expected.