Wind slabs lingering in steep terrain and deeply buried weak layers are demanding careful terrain selection right now.
Recent strong southerly wind formed wind slabs on north-facing terrain. Assess for slabs prior to committing to steep terrain. Keep in mind that a wind slab release could also act as a trigger for the deeply buried late-December weak layer.
Triggering persistent slab avalanches remains possible due to several weak layers in the top metre of the snowpack. Facet layers are the primary concern in alpine terrain, while preserved surface hoar layers are the concern in treeline terrain.
A very large (size 3) persistent slab avalanche was remotely triggered on Sunday. This avalanche failed on a 50 cm deep facet layer and released on a northeast aspect at 1900 m. We continue to get evidence that this persistent slab can be easily triggered by riders in specific areas.
Otherwise, there were several reports of smaller (size 1 to 2) wind slab avalanches over the weekend, primarily occurring on north-facing aspects.
Recent strong southerly wind formed wind slabs in lee terrain features near ridges. Exposed solar aspects may have formed a surface crust. Light flurries and and winds aren't expected to do much to change these conditions on Wednesday.
More importantly, several persistent weak layers may be found in the top meter of the snowpack. These include a surface hoar layer buried on Dec 28 found 40 to 60 cm deep and a facet layer buried on Dec 23 found 60 to 100 cm deep. In alpine terrain, triggering one of these layers is most likely on steep rocky slopes where they present as facets. In treeline terrain, the layers are most likely triggered on steep slopes in open trees where they present as preserved surface hoar.
Tuesday night
Cloudy with light south winds.
Wednesday
Mostly cloudy with flurries bringing up to 5 cm of new snow. Light south winds. Treeline high temperatures around -6 °C.
Thursday
Clearing, with valley cloud remaining below about 1500m. Moderate southeast winds. Treeline high temperatures around -5 under a mild temperature inversion.
Friday
Mainly cloudy with isolated flurries. Light to moderate southeast winds. Treeline high temperatures around -5.
More details can be found in the Mountain Weather Forecast.
