Wind slab formation will be of greatest concern in the south of the region, where upwards of 20 cm of low density snow sits on top of a crust. Elsewhere, thinner isolated pockets can still be surprisingly reactive as they are likely poorly bonded to underlying surfaces.
Small inputs of new snow along with moderate wind will feed wind slabs in the alpine and upper treeline. Watch for fresh deposits in lee terrain features.
Low density surface snow that hasn't formed a slab may also slide easily on a slippery crust.
A buried weak layer may exist at upper elevations. Large loads such as wind slab releases have potential to trigger this layer to produce very large, destructive avalanches.
Sunday night: A trace of new snow. Moderate southwest wind. Treeline temperature around -13.
Monday: Flurries around 5 cm. Light to moderate northwest wind. Treeline high temperatures around -8.
Tuesday: Cloudy with flurries starting in the afternoon. Strong southwest wind. Treeline high temperatures around -3.
Wednesday: New snow 10-20 cm. Strong southwest wind. Treeline high temperatures around -8.
On Saturday, some loose dry sluffing and thin soft slab reactivity were seen in steep terrain and near ridge crests in the neighboring Sea to Sky region. The most recent reports we have from the inland are of explosives producing a size 2 wind slab avalanche in the Hurley on Thursday.
5-20 cm of new low density snow may sit over a widespread layer of small surface hoar crystals which we will continue to monitor going forward. This sits over wind affected snow in the alpine and a thick, supportive crust below 1800 m. Between 1800-2100 meters, this crust exists shallowly buried by wind affected snow.
A couple of buried weak layers produced large avalanches during a previous storm. Snowpack models and observations in the neighboring Sea to Sky region indicate that these layers have been reset by previous rain at treeline, but uncertainty remains around their status in the alpine. These include a layer of surface hoar down an estimated 90-120 cm and deeper crust/facet combo layer.
Average snowpack depths in the alpine are now likely closer to 150-200 cm. Below treeline, depths of 30-50 cm have been reported around 500 m, decreasing dramatically with elevation, and still below threshold for avalanches in many areas. Early season hazards such as rocks, stumps, and creeks are still a concern below the alpine.
