Triggering slab avalanches is possible on steep and convex slopes in treeline and alpine terrain.
Wind-affected areas are reported as having reactive soft slabs above a layer of surface hoar. Use caution around convexities or sharp changes in terrain.
Two persistent weak layers in the top meter of the snowpack continue to show potential for human triggering. The first, found 40 to 70 cm deep, is a layer of facets formed during the prolonged period of arctic air. Surface hoar could may be found at this interface in sheltered treeline features. The second is a layer of facets and surface hoar from early December that is buried as deep as 100 cm in some areas.
Both these layers are most concerning in sheltered features at treeline where surface hoar is more likely to be present.
Recent avalanche activity has been relatively quiet, with primarily small (size 1) wind slabs and dry loose avalanches reported on Sunday and Monday. However, we continue to get periodic reports of large human-triggered persistent slab avalanches. Most recently, two size 2 persistent slabs were triggered on treeline features in the northern part of the region on Monday. These avalanches failed on 30 to 50 cm deep facet layers. Similar avalanches were reported in treeline terrain in southern parts of the region last Thursday and Friday. This ongoing activity suggests it is still possible to trigger persistent slabs in specific alpine and treeline terrain features.
Shifting winds are redistributing 15 to 30 cm of recent snow leaving wind slabs on lee terrain features. Wind slabs are also likely found on cross-loaded features in coastal inlets due to outflow winds. Below 1000 m a crust exists on or near the surface.
40 to 70 cm overlies a weak layer that formed during the Arctic outbreak in mid-December. In the alpine this layer is generally facets, but some surface hoar has been reported. At treeline, it is more likely to find surface hoar at this interface in sheltered terrain.
A layer of surface hoar and facets from early December can be found down 70 to 100 cm. This layer has not been reactive recently, although still produces some sudden results in snowpack tests.
Tuesday night
Cloudy with isolated flurries and trace accumulations of snow, 40 km/h wind from the southeast, treeline temperatures drop to -8 °C.
Wednesday
Partly cloudy in the morning with sunny periods in the afternoon, no precipitation, 20 km/h wind from the east, treeline temperatures around -4 °C.
ThursdayMix of sun and cloud, no precipitation, 30 to 50 km/h wind from the southeast, treeline temperatures around -6 °C.
FridayCloudy with flurries increasing in intensity throughout the day, 5 to 10 cm of snow by the late afternoon, 40 to 60 km/h wind from the south, treeline temperatures warm to -3 °C.
More details can be found in the Mountain Weather Forecast.
