New snow and wind are forming fresh, reactive slabs in lee terrain features at upper elevations. Be prepared to dial back your terrain choices if you see signs of instability such as shooting cracks or recent avalanches.
New snow and wind are forming fresh slabs. They are most likely to be reactive in wind loaded features and where the new snow sits over surface hoar or a crust. In the north of the region near Revelstoke where snowfall amounts are higher, a more widespread storm slab problem may exist.
The early December crust can be found down 80 to 200 cm below the surface, with a weak layer of facets on top of it. The likelihood of triggering an avalanche on this layer is decreasing but still remains a concern for avalanches stepping down. We are now in a low probability/high consequence scenario with this layer.
Sunday night: Snowfall 5-10 cm, moderate SW wind, freezing levels around 600 m.
Monday: Snowfall 5-10 cm, moderate SW wind, freezing levels reaching around 1000 m.
Tuesday: A mix of sun and cloud, light variable wind, freezing levels near valley bottom.
On Saturday, small wind slabs on E-NE aspects in the alpine were reactive naturally and to ski cuts
A warm storm on Wednesday and Thursday last week triggered a widespread natural avalanche cycle up to size 3.5 (very large) at upper elevations. At lower elevations, loose wet activity was widely observed. By Friday, natural storm slab activity had largely tapered in size and number, but explosive control work continued to produce results up to size 2.
As of Saturday, observations continue to roll in from throughout the region of several persistent slab avalanches on the early December layer, suspected to have run during the warm storm Wednesday/Thursday. These avalanches are generally around 2100 m, size 2.5-3.5 (very large), 100-150 cm deep and on NE-NW aspects.
New snow falls over 25-50 cm of well settled snow from the previous storm, possibly a layer of surface hoar crystals in sheltered areas, and/or a thin breakable crust which was observed as high as 1800 m in the Selkirks and into the alpine in the Monashees.
A couple of layers of weak facets and/or surface hoar that were buried earlier in January now sit 25-50 cm and 60-90 cm deep.
The early December crust/facet interface is now typically down 80-140 cm, but as deep as 200 cm in wind loaded terrain. It consists of faceted grains above a decomposing crust formed by the Atmospheric River rain event at the end of November. There has been avalanche activity on this layer as recently as recently as Friday in the region. Heavy triggers like natural cornice falls and storm slab avalanches may still have potential to step down to this layer resulting in very large avalanches.
This video from our field team provides some additional insight into the snowpack in the south of the region.
