Avalanche Forecast
Issued: Jan 6th, 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.
MBender,
Avalanche Canada
Up to 30 cm of new snow Tuesday day night fell with strong to extreme wind from a variety of directions. As a result storm and wind slabs will remain the main concern on Thursday.
Summary
Confidence
Weather Forecast
Wednesday Night: Mainly cloudy, light to moderate southeast wind, alpine high -5.
Thursday: Mainly cloudy, light southwest wind, alpine high -5, freezing level 500m.
Friday: Flurries, 3-5 cm, moderate southerly wind, alpine high -3, freezing level 800 m.
Saturday: Flurries, light southwest wind, alpine high -4, freezing level 700 m.
Avalanche Summary
On Wednesday there were several size 2 explosives controlled storm slab avalanches reported running in the alpine and treeline.
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.
A large, natural storm slab avalanche cycle size 3-4 occurred near Pemberton over the weekend. Natural and explosive triggered storm slabs size 1-2 were reported elsewhere. This MIN report from Friday illustrates the active avalanche conditions during the weekend storm.
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
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- 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.
Problems
Storm Slabs
Snowfall combined with wind Tuesday night has created reactive storm slabs. Strong to extreme wind from a variety of directions has likely created deep deposits in exposed lee terrain.
Aspects: All aspects.
Elevations: All elevations.
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. These layers have shown a downtrend in activity since early last week but there remains potential for avalanches to step down to these layers.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 7th, 2021 4:00PM
