Wind slab
- Above treeline
Freshly generated snowdrifts atop unfavorable old snowpack
Freshly generated snowdrifts atop unfavorable old snowpack
Freshly generated snowdrift accumulations are prone to triggering, occur in steep terrain near to and distant from ridglines, behind drops in the landscape, in gullies and bowls in all aspects. Danger zones rapidly increase in frequency and in size with altitude above the timberline. Marked weak layers in the old snow can be triggered by winter sports enthusiasts, particularly on steep, little-skied on slopes. Avalanche prone locations are impossible to see, require a defensive route selection. Avalanches superficially triggered can fracture down to deeper layers inside the snowpack and grow to medium size. Whumpf noises and fractures on the surface are alarm signals.
As a result of fresh snowfall, fresh snowdrift accumulations which are prone to triggering are being generated. Focal point of precipitation is in the western barrier cloud regions to the Arlberg region and Allgau Alps: 10-15cm of snowfall plus storm-strength winds. Fresh snow and drifts will be deposited on top of an often melt-freeze encrusted surface, and surface hoar. Particularly on steep shady high-altitude slopes, markedly weak layers occur inside the old snowpack.
At the end of a nocturnal front, clouds will dissipate, possibly leaving some residual high fogbanks behind. Elsewhere, slightly cloudy, increasing sunshine in the mountains. Temperature at 2000m: -6 to -2 degrees; at 3000m: -10 degrees. Winds at high altitudes will taper off, shift to southwesterly (but remain strong in the classic foehn-exposed zones).
Snowdrifts deposited on the weak old snowpack remain prone to triggering
Bulletin data: Avalanche Warning Service Vorarlberg (CC BY 4.0)