The main concern is wind slabs in exposed terrain, which may rest on a weak surface hoar layer in some areas, increasing their reactivity.
Wind slabs have built 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 point.
Numerous avalanches were reported across the region in the alpine and treeline on Tuesday. Most were small wind slabs and loose dry slides, size 1 to 1.5, with a few larger size 2 reported. Several were triggered by riders, with naturally triggered avalanches also observed.
Avalanche activity over preceding days also involved wind slabs. At least one ran on a surface hoar layer buried in early January on a southwest alpine aspect.
Up to 15 cm of low-density new snow has fallen over the last few days, with another 0 to 5 cm expected by 4 pm Thursday. This snow has buried a variety of surfaces including sun crust, surface hoar and facets.
The snow surface is likely wind-affected in most open areas at all elevations.
A secondary layer of weak surface hoar from early January is buried 25 to 50 cm. This layer has most recently only been reactive where wind slabs have formed above it.
A crust/facet/surface hoar layer from early December may be found 90 to 160 cm deep. Avalanche activity on this layer has tapered in recent weeks.
Wednesday Night
Mainly cloudy with isolated flurries, accumulation 0 to 4 cm. 10 to 30 km/h variable ridgetop wind. Treeline high temperature -15 °C.
Thursday
Increasing cloud, with scattered flurries, accumulation 2 to 6 cm. 25 to 35 km/h westerly ridgetop wind. Treeline high temperature -9 °C.
Friday
A mix of sun and cloud. 30 to 45 km/h northwest ridgetop wind. Treeline high temperature -12 °C.
Saturday
Sunny. 15 km/h northwest ridgetop wind. Treeline high temperature -12 °C.
More details can be found in the Mountain Weather Forecast.
