Storm slab avalanches will become more likely throughout the day as the new snow accumulates and buried the surface hoar crystals and the melt-freeze crust.
A storm slab avalanche problem will develop throughout the day as the new snow accumulates and buried the surface hoar crystals and the melt-freeze crust.
A concerning weak layer of faceted grains above a melt-freeze crust is around 70 to 150 cm deep. We have been receiving reports of large, destructive avalanches on this layer every few days. We've been reminded multiple times over the last month that this layer could remain a concern all winter. Thin rocky start zones are the most likely place to trigger this layer. Snow loading from new snow and/or wind, daytime warming, cornice falls, and step-downs from smaller avalanches could increase the chance of an avalanche on this layer. Learn more about this crust and how to deal with it in this forecasters' blog.
The weather pattern is changing as the upper ridge of high pressure over B.C. has flatten allowing the Pacific system to move over the province.
SATURDAY NIGHT: Increasing cloudiness with isolated flurries, accumulation 1 to 3 cm, 30-40 km/h southwesterly winds, low alpine temperature -10 C with freezing level at valley bottom.
SUNDAY: Cloudy with snowfall, accumulation 5 to 10 cm during the day and 10 to 20 cm overnight, 30-50 km/h southwesterly winds, high alpine temperature -5 C with freezing level at valley bottom.
MONDAY: A mix of sun and cloud with isolated flurries, accumulation 1 to 3 cm, 30-40 km/h westerly winds, high alpine temperature -7 C with freezing level at valley bottom.
TUESDAY: A mix of sun and cloud with scattered flurries, accumation 3 to 5 cm, high alpine temperature -10 C with freezing level at valley bottom.
No recent avalanches have been reported.
Avalanche activity on the early-December weak layer described in the snowpack summary has been sporadic over the past few weeks. We tend to see reports of avalanches on this layer every few days, being triggered naturally from the weather or occasionally by riders. Most of the avalanches occurred at elevations around 2000 m. Possible natural triggers include daytime warming, warming from the sun, cornice falls, or smaller avalanches stepping down. Human triggering is most likely in steep, rocky slopes with a shallow or thin-to-thick snowpack.
Alpine terrain has widespread wind effect. Surface hoar crystals are found in sheltered areas and a melt-freeze crust on solar aspects. These will be important layers to track as they get buried by new snow.
Some older thin surface hoar layers are 20-40 cm deep, but have not been producing concerning results in recent snowpack tests.
The most notable layer of concern in the snowpack is a facet/crust layer that formed in early December and ranges in depth between 70 cm along the shallower eastern Purcells and up to 150 cm in the western Purcells.
