Isolated wind slabs and large overhanging cornices may remain triggerable by humans. Give cornices their space when travelling on ridgetops and check your line for pockets of wind slab beneath ridge crests and on steep roll-overs.
Previously formed wind slabs may remain triggerable by human traffic in isolated terrain features. Cornice falls could also act as potential triggers for avalanches on wind loaded slopes below.
Cornices have grown large, saggy and fragile. A few recent cornice falls have triggered wind slab avalanches on the slopes below.
Wednesday night: Partly cloudy, light wind, freezing level valley bottom.
Thursday: Mix of sun and cloud, light wind, alpine high around -8.
Friday: Sunny, light wind, alpine high -12.
Saturday: Sunny, light wind, alpine high -12.
On Tuesday, we received report of a thin wind slab size 1.5 triggered naturally in a confined treeline feature. Cornice falls in the northern parts of the region have been reported over the last few days. Many of them triggered wind slab avalanches up to size 2 in the slopes below. None of these large loads triggered deep persistent layers.
In the south of the region, fluctuating freezing levels during the last storm have resulted in a crust to ridgecrest. At upper elevations, 5-10 cm of dry snow has been blown around by the wind, exposing the crust in some areas and building wind slabs on top of it in others. The lower snowpack is well settled.
In the north, upper elevations are extensively wind affected. A widespread surface crust exists below 1600 m. Remnants of a melt-freeze crust from early December may be found around 200 cm deep in the snowpack. It has been most prevalent northwest of Pemberton where large avalanches failed on this interface earlier this month. Recent reports and snow profiles suggest that this layer is decomposing and/or bonding to surrounding snow and trending dormant... for now at least.
