New wind slabs should form with forecast weather, but they may not be the greatest concern. Recent reports point to a layer of surface hoar making existing wind slabs especially reactive.
New snow and wind should form small new slabs, but triggerable wind slabs already exist below ridgetops and in cross-loaded terrain. A layer of surface hoar buried in early January has kept them surprisingly reactive.
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.
On Saturday and to a lesser extent through the early part of the week, there have been numerous, small accidentally triggered wind slab avalanches. The recent layer of surface hoar was usually noted as the failure plane. One very large (size 3) wind slab avalanche was triggered by a skier in neighbouring Glacier National Park.
Light new snow and elevated winds through Thursday shouldn't do much to alter presently wind-affected surfaces in open areas at all elevations.
In sheltered terrain, we may see up to 10 cm added to the present 30 to 40 cm of settling snow sitting on a layer of weak, feathery surface hoar crystals that exists into the alpine. On sunny slopes and below about 1500 m it should bury a melt-freeze crust of varying thickness. Wind slabs formed over the surface hoar have been reactive. Small new slabs forming on the new crust may be similar.
A crust/facet/surface hoar layer buried in early December may be found 90 to 160 cm deep. Activity on this layer has tapered significantly in the last couple of weeks.
Wednesday night
Cloudy with increasing flurries bringing an initial trace of new snow. 30 to 60 km/h southwest ridgetop wind, increasing. The incoming storm will scour away the above freezing layer lingering between 1700 and 2500 m.
Thursday
Cloudy with continuing with scattered flurries bringing 5 - 10 total cm of snow. 40 to 50 km/h southwest ridgetop wind shifting northwest and easing. Treeline temperature falling to -6 °C.
Friday
Mainly cloudy with isolated flurries. 30 km/h northwest ridgetop wind. Treeline temperature falling to -8 °C.
Saturday
Mainly sunny. 20 km/h northwest ridgetop wind. Treeline temperature around -13 °C.
More details can be found in the Mountain Weather Forecast.
