Avalanche Forecast
Issued: Jan 2nd, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
ahanna,
Avalanche Canada
The storm continues and avalanche activity is expected to remain widespread. Avoid avalanche terrain.
A complex snowpack has produced large avalanches and several incidents in the last week, including a fatal avalanche near Pemberton on Monday.
Summary
Confidence
Weather Forecast
Saturday night: Snow, 10-30 cm, wind easing to moderate southwest, freezing level dropping to 800 m.
Sunday: Snow, 10-20 cm, moderate southwest wind, alpine high temperature near -7, freezing level 800-1000 m.
Monday: Flurries, 5-10 cm, light southwest wind, alpine high temperature near -4, freezing level 1000 m
Tuesday: Flurries, 5-10 cm, southwest wind increasing to strong, alpine high temperature near -7, freezing level 1000 m.
Avalanche Summary
Avalanches are expected to be large and widespread on Sunday, storm slabs as well as persistent slab avalanches.
Numerous storm slab avalanches, natural and explosive triggered size 1-4 (!) were reported on Saturday. This MIN report from Friday illustrates the active avalanche conditions during this storm.
Several large persistent slab avalanches have been reported over the previous week:
There was a fatal avalanche in the South Coast Inland region (near the Sea to Sky boundary) 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 2.5 avalanche was triggered on Monday by a skier on Rainbow Mountain, which resulted in a full burial and, thankfully, a successful rescue. The avalanche failed on a 60 cm deep crust and facet layer on a northeast aspect around 1800 m.
A natural size 3 persistent slab avalanche was reported on Mount MacBeth on Monday, check out this MIN report for details of this observation.
These avalanches highlight the ongoing potential to trigger persistent weak layers in the snowpack.
Snowpack Summary
There may be as much as 20-50 cm of new snow between Saturday night and Sunday afternoon, forming widespread storm slabs. This brings recent storm totals to well over 100 cm.
The snowpack is currently quite complex. The layer of greatest concern is a melt-freeze crust from early December, found around 100-200 cm deep in the snowpack. This crust may have surface hoar or sugary faceted grains sitting above it. There have been several recent large natural and human triggered avalanches on this layer.
The remainder of the snowpack is well-settled.
Terrain and Travel
- Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
- Avoid areas with overhead hazard.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
- Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
Problems
Storm Slabs
Storm slabs will be widespread and very reactive due to significant snow amounts and strong winds.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A couple of problematic layers may be found around 50 to 150 cm deep, including weak layers of surface hoar and faceted grains above a hard melt-freeze crust. With the addition of a significant load of new snow, large avalanches may run naturally on these layers.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 3rd, 2021 4:00PM
