If the storm arrives earlier than expected, danger may increase during the day. Danger may be HIGH by Friday afternoon in the south of the region.
There was a fatal avalanche near Pemberton on Monday. Stick to low-angle terrain at all elevations and avoid overhead hazard.
Weak layers of surface hoar and/or faceted grains may be found above a melt-freeze crust. Recent reports suggest this weak layer may be less prevalent in the south of the region, but still exists in localized pockets.
Strong winds and fresh snow will mean that new, reactive storm slabs are likely to form and they may become increasingly reactive throughout the day.
THURSDAY NIGHT - Flurries, 5-10 cm / southwest wind, 30-50 km/h / alpine low temperature near -3
FRIDAY - Snow, 10-20 cm, with another 10-20 cm overnight / southwest wind 40-60 km/h, gusting to 90 km/h / alpine high temperature near -1 / freezing level 1200 m
SATURDAY - Snow, 5-10 cm, with another 15-20 cm overnight / southwest wind 30-60 km/hr, gusting to 80 km/hr/ alpine high temperature near -2 / freezing level 1500 m
SUNDAY - Snow, 10-15 cm / southwest wind 40-60 km/h / alpine high temperature near -2 / freezing level 1200 m
Fresh storm slabs are expected to form on Friday. The bulk of the storm is expected to hit in the afternoon, which may mean that avalanche activity could increase throughout the day. The new snow load may also increase the potential for natural and human triggered persistent slab avalanches.
There was a fatal avalanche north of Pemberton in the Railroad Pass area on Monday that resulted in two fatalities. It was reported to be a size 2 persistent slab avalanche on a west aspect, around 1650 m. The RCMP press release can be viewed here and the Avalanche Canada report can be found here.
A size 2 avalanche was triggered on Monday by a skier on a northwest aspect in the alpine on Mt. Matier (Duffey). The avalanche occurred on a northwest aspect and was likely a wind slab avalanche. It carried the skier over cliffs resulting in several injuries. A MIN report detailing this incident can be found here.
A few persistent slab avalanches were reported last week, mostly in the north of the region near the Hurley, but also near Allison Pass. They were triggered by riders, heavy machinery, and naturally. The slabs were generally 60 to 90 cm deep, around 2000 m, and released on the weak layers described in the snowpack summary.
5-10 cm of new snow on Thursday night will bring recent storm snow totals to about 20-35 cm, which may be sitting on surface hoar below treeline. Strong southwest winds Thursday night and during the day on Friday will likely be forming fresh wind slabs. More snow is expected to arrive on Friday afternoon.
A melt-freeze crust from early December is found around 40 to 120 cm deep in the snowpack. This crust may have feathery surface hoar or sugary faceted grains sitting above it. This persistent weak layer is most prevalent in the north (e.g., Duffey Lake, Hurley) and found to a lesser extent in the south of the region.
The remainder of the snowpack is generally well settled.
