Avalanche danger will increase rapidly as heavy snowfall blankets the region through Saturday - with the greatest accumulations expected along the BC/Alberta border. Back off to simple terrain that is free of overhead hazards as depths increase - and enjoy the new snow!
Heavy snowfall is expected to drive the formation of new storm slabs throughout the day on Saturday. New snow is not expected to bond well with the current snow surface and wind will likely accelerate slab formation in open areas.
Weak snow at the bottom of the snowpack hasn't gone away, and will be an increasing concern as rapid loading and avalanches in surface layers strain the snowpack on Saturday. Evidence of deep persistent slab avalanches has been focused in the Sparwood-Elkford area over the past month. Human triggering is most likely around steep rocky terrain features, or anywhere the snowpack is thin and weak.
Friday night: Cloudy with increasing flurries bringing 5-10 cm of new snow. Moderate southwest winds.
Saturday: Cloudy with continuing snowfall bringing 15-25 cm of new snow. Light south winds, becoming moderate or strong at ridgetop. Alpine high temperatures around -7.
Sunday: Mainly cloudy. Light to moderate southwest winds. Alpine high temperatures around -9.
Monday: Mainly sunny. Light to moderate southwest winds. Alpine high temperatures around -8.
No avalanches have been reported since last week, but there have been limited field observations. A few natural size 2 wind slabs have been reported on north and east aspects in the neighbouring Kananaskis region.
A very large (size 3) deep persistent slab avalanche was observed north of Sparwood last Friday on a steep southeast facing alpine slope. This follows a pattern of sporadic deep slab releases in the upper Elk Valley including this natural avalanche from Feb 11 and this sled triggered avalanche from Feb 9. These types of large avalanches will be most likely during periods of heavy loading or intense warming.
20-30 cm of new snow is expected to accumulate in the region by the end of the day on Saturday, targeting the east slope of the region in particular. The new snow will bury recent wind slabs and wind effect in exposed terrain as well as sun crust on solar aspects and temperature crust up to 1700 m on all other aspects. The new snow is not expected to bond well with any of these surfaces over the near term.
A thick rain crust currently sits 40-80 cm below the surface and can be found up to 2100 m. Avalanche activity was last observed at the faceting interface between this crust and overlying snow on February 17. The mid-pack is well settled and strong, but the base of the snowpack contains basal facets that are most prominent in shallow rocky start zones.
