Not all wind slabs are created equal. Many recent avalanche reports point to a failure layer of surface hoar that will keep slabs reacting to human triggers for longer than you might expect.
Rider-triggerable slabs may be found below ridgetops and in cross-loaded terrain. A layer of surface hoar buried in early January is reaching a tipping point as slabs form over it. Triggering it could lead to wide propagations.
On Monday, a snowcat west of Revelstoke triggered a small slab which failed on the early December weak layer. It was at treeline on a west aspect.
We also have a report of a very large (size 3) wind slab avalanche triggered by a skier in neighbouring Glacier National Park.
On Saturday there were numerous, small accidentally triggered wind slab avalanches. A newer layer of surface hoar was noted as the failure plane.
Saturday's moderate northwest wind has affected the surface in open areas at all elevations.
In sheltered terrain, 30 to 40 cm of settling snow sits on a layer of weak, feathery surface hoar crystals, possibly even into the alpine. On sunny slopes, there may be a crust as well.
A crust/facet/surface hoar layer buried in early December may be found 90 to 160 cm deep.
Tuesday night
Cloudy with isolated flurries. 10 to 15 km/h southwest ridgetop wind. An above freezing layer lingering between 1700 and 2500 m.
Wednesday
A mix of sun and cloud with isolated flurries. 10 to 30 km/h southwest ridgetop wind, increasing. Above freezing layer lingering between 1700 and 2500 m. Treeline temperature around 0 °C.
Thursday
A mix of sun and cloud with scattered flurries bringing 1 to 5 cm of snow. 40 to 60 km/h southwest ridgetop wind. Above freezing layer breaking down and treeline temperature falling to -6 °C.
Friday
Mainly cloudy with isolated flurries. 30 km/h northwest ridgetop wind. Treeline temperature falling to -8 °C.
More details can be found in the Mountain Weather Forecast.
