Use extra caution in wind-loaded areas at treeline, where wind slabs have formed over a weak layer of surface hoar.
Carefully assess open areas and convex slopes, especially at treeline, where surface hoar may be preserved.
Wind-affected areas are reported as having soft slabs above a layer of surface hoar. Slabs have been reactive to skier traffic. Use caution around convexities or sharp changes in terrain.
There are two persistent weak layers in the top meter of the snowpack. The first, found 20-40 cm down, is a layer of facets formed during the prolonged period of arctic air. Surface hoar could also be found at this interface in sheltered treeline features.
The second is a layer of facets and surface hoar from early December. This layer is buried as deep as 1 meter in some areas.
Both these layers are most concerning in sheltered features at treeline and below where surface hoar is more likely to be present.
On Sunday, there were reports of several small natural wind slab avalanches. Soft slabs developed by wind above a layer of surface hoar were reactive to skier traffic on isolated features and convex rolls up to size 1.
On Friday, a skier accidental persistent slab avalanche was reported. The size 1.5 avalanche slid on a layer of depth hoar and facets close to the ground.
Last week several avalanches were reported at treeline and below on the layer of facets formed during the recent period of arctic air. Though natural activity has tapper off human-triggering remains possible on this layer.
+20 cm of new snow has buried a widespread layer of surface hoar in sheltered areas at treeline. Wind-affected surfaces are found in exposed areas at higher elevations and below treeline cross-loading will likely be found in all coastal inlets due to recent outflow. Below 1000 m a crust exists on or near the surface.
40 to 70cm overlies a weak layer formed during the previous period of arctic air. In the alpine this layer is generally facets but surface hoar could be found. 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 100cm. recently this layer has not been reactive but still produces sudden results in snowpack tests.
Monday Night
Mainly cloudy with isolated flurries, 1-5 cm accumulation. Ridgetop winds southerly 30 to 50 km/h. A low of -5 at 1500m. Freezing levels 400m.
Tuesday
Cloudy with sunny periods and isolated flurries, trace accumulation. Ridgetop winds southerly 20 km/h. A high of -5 at 1500m. Freezing levels 300m.
Wednesday
Mostly cloudy with sunny periods with isolated flurries, trace accumulation. Ridgetop winds southerly 20 km/h. A high of -6 at 1500m. Freezing levels 300m.
Thursday
Mix of sun and cloud. Ridgetop winds southerly 20 km/h. A high of -5 at 1500m. Freezing levels valley bottom.
More details can be found in the Mountain Weather Forecast.
