Avalanche Forecast
Issued: Jan 4th, 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
Recently formed storm slabs will be most reactive in wind affected areas at upper elevations and human triggering in these areas is likely. Be especially cautious as you transition into wind affected terrain.
Summary
Confidence
Moderate - Uncertainty is due to whether buried persistent weak layers become active, triggering avalanches, with the arrival of the forecast weather.
Weather Forecast
Monday night: Snow, 5-10 cm, moderate to strong south wind, freezing level 500 m.
Tuesday: Sun and cloud, moderate southwest wind, alpine high -7, freezing level 800 m.
Wednesday: Snow, 5-15 cm, moderate southwest wind easing, alpine high -4, freezing level 1200 m.
Thursday: Snow, 5-10 cm, light northwest wind, alpine high -5, freezing level 1100 m.
Avalanche Summary
Numerous natural, human and explosive triggered storm slabs size 1-2.5 were reported on Saturday and Sunday. Check out this avalanche triggered remotely by a skier in Kootenay Pass on the weekend.
Sporadic reports of persistent slab avalanches have been popping up, including a natural size 3 near Whitewater on Sunday. With new snow slowly but steadily piling up, the chances of a resurgence of persistent slab avalanches will increase. This incremental loading makes it difficult to predict when the tipping point will be reached. The uncertainty around this problem is best managed with conservative terrain selection.
Snowpack Summary
30-60 cm of recent storm snow has seen significant wind affect at upper elevations. In sheltered areas, the recent snow may sit over surface hoar.
Two weak layers are buried in close proximity to one another. They are 70-100 cm deep around Nelson and 50-80 cm deep around Rossland and other western parts of the region. The layers are composed of feathery surface hoar and sugary faceted grains and they overlie a hard melt-freeze crust.Â
Terrain and Travel
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Keep in mind that human triggering potential persists as natural avalanching tapers off.
- Be especially cautious as you transition into wind affected terrain.
- Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
Problems
Storm Slabs
Storm slabs may remain sensitive to human triggers, especially in freshly wind loaded features at upper elevations and where recent snow sits over surface hoar in wind sheltered areas.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Weak surface hoar and/or faceted grains sit above a melt-freeze crust 70 to 100 cm deep. This layer is being stressed as new snow slowly but steadily piles up. This incremental loading makes it difficult to predict when the tipping point will be reached. We are currently seeing only sporadic avalanches running on these layers, but they have been large (size 3). The uncertainty around this problem is best managed with conservative terrain selection.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 5th, 2021 4:00PM
