Raise your guard as you reach wind-affected terrain or encounter signs of instability like shooting cracks. Weak grains below the storm snow have led to surprisingly reactive wind slabs.
Human-triggerable wind slabs exist below ridges and in cross-loaded terrain on a variety of aspects. A layer of surface hoar buried in early January has kept slabs surprisingly reactive, sometimes propagating well above the trigger.
Last weekend and more sporadically through the week, there have been many accidentally triggered wind slab avalanches, mostly small, but occasionally up to size 2.5. One of these larger releases was triggered by skiers entering a couloir on the north side of Mt English on Wednesday. The early January surface hoar (occasionally sitting on a thin crust) has frequently been noted as the failure plane in these avalanches.
Wind-affected surfaces predominate in open areas at all elevations. Where protected, up to 30 cm of snow now covers a mid-January layer of crusts below treeline and on solar aspects and surface hoar in the shade.
10 to 40 cm of snow since early January has been settling on a layer of weak surface hoar crystals that exists into the alpine. The presence of slab properties over these grains has been the main factor determining whether it is a problem. Wind slabs formed over it have been reactive.
A crust/facet/surface hoar layer from early December may be found 90 to 160 cm deep. Activity on this layer has tapered, but it is still factoring into professional assessments in the Selkirks north of Kaslo.
Sunday night
Clear and starry. 15 to 30 km/h north ridgetop wind. Treeline low temperature -23 °C.
Monday
Sunny. 10 to 15 km/h west or northwest ridgetop wind. Treeline high temperature -12 °C with a possible temperature inversion.
Tuesday
Cloudy with isolated flurries, trace to 5 cm of new snow. 20 to 40 km/h west ridgetop wind. Treeline high temperature around -12 °C.
Wednesday
Mostly cloudy. 20 to 50 km/h west ridgetop wind. Treeline high temperature -8 °C.
More details can be found in the Mountain Weather Forecast.
