Avalanche Forecast
Issued: Jan 7th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
MBender,
Avalanche Canada
Heightened avalanche conditions exist on wind loaded slopes and steep rocky terrain. Although the likelihood of triggering deeply buried weak weak layers is reducing, the consequences of doing so are still high.
Summary
Confidence
Moderate - Uncertainty is due to the complexity of the snowpack’s structure.
Weather Forecast
Thursday Night: Mainly cloudy, moderate southeast wind, alpine high -7, freezing level at valley bottom.
Friday: Scattered flurries, 5 cm, moderate to strong southerly wind, alpine high -5, freezing level 700 m.
Saturday: Mainly cloudy with sunny breaks, light south wind, alpine high -4, freezing level 800 m.
Sunday: Mainly cloudy with flurries, moderate southwest wind, alpine high -3, freezing level 1000 m.
Avalanche Summary
On Thursday there was a report of a remotely triggered (from a distance of 20m) size 2.5 deep persistent slab avalanche on a west aspect at 1930 m on Cowboy Ridge. The fracture line was up to 200 cm deep.
On Wednesday there were numerous size 2 explosives controlled storm slab avalanches reported running in the alpine and treeline. As well there were several persistent and one deep persistent slab size 2.5-3 ranging in depth from 100-150 cm.
Reports on Monday and Tuesday show a few explosives controlled storm slab avalanches running size 1-2 as well as a few human triggered storm slab and loose dry avalanches size 1-1.5.Â
Snowpack Summary
Over 150 cm of recent storm snow from the past week has seen extensive wind effect at upper elevations, with scoured windward aspects, wind slabs in lee features and growing cornices at ridgetop.
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 and new snow loads as well as large loads from storm slab avalanches have potential to trigger these layers.
Terrain and Travel
- Be especially cautious as you transition into wind affected terrain.
- Be mindful that deep instabilities are still present and have produced recent large avalanches.
- If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
- Cornice failure may trigger large avalanches.
Problems
Wind Slabs
Strong to extreme southerly wind Tuesday night has created widespread wind effect. Expect to see deep wind deposits in exposed lee terrain.
Aspects: North, North East, East, South West, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A couple of problematic layers may be found around 100 to 200 cm deep, including weak layers of surface hoar and faceted grains above a hard melt-freeze crust. Sporadic avalanche activity on these layers this week means there is still potential for avalanches to step down to these layers.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 8th, 2021 4:00PM
