Avalanche Forecast
Issued: Dec 18th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Persistent Slabs and Loose Dry.
Mark Herbison,
Expect the new storm slab and dry loose avalanches to be reactive on Sunday as the storm tapers off.
The Dec 1 persistent weak layer is a growing concern. Assess the snowpack before committing to larger avalanche terrain.
Summary
Weather Forecast
Snow will continue to fall until early Sunday morning, with another 10cm of accumulation overnight, totalling ~30cm in the storm. As the storm leaves the region, the winds and temps will drop with an alpine high of -15 as an arctic high pressure system settles in for a few days. Clearing skies and cooler temps for Monday and Tuesday.
Snowpack Summary
Excellent snow quality can be found throughout the Park wit 20cm of new snow over the past 24 hours, totalling ~30cm in the last few days. The Dec 1 crust is ~10cm thick, buried a ranging depth of 50-100cm, and can be found up to 2300m. Facets observed above and below this crust, particularly in shallow snowpack areas at and just below tree line.
Avalanche Summary
Limited visibility due to the raging winter storm, but suspect a natural avalanche cycle up to sz 3.0 to occur by early Sunday morning.
Snowpack tests continue to give sporadic sudden results on the Dec 1 crust, particularly in shallower snowpack areas at tree line.
Confidence
Problems
Storm Slabs
~30cm of new snow is falling onto previously facetted surfaces and is not expected to bond quickly. Moderate winds will build deeper slabs in leeward areas.
- Use caution in lee areas in the alpine and treeline. Storm snow is forming touchy slabs.
- Be careful of loose dry power sluffing in steep terrain.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
The Dec 1st crust is buried by 50-100 cm of snow. The crust is most reactive at tree line, but it is present below tree line and in the lower alpine. Be especially cautious in thinner snowpack areas, where it is more likely to be reactive.
- If triggered the storm slabs may step down to deeper layers resulting in large avalanches.
- Avoid steep convexities or areas with a thin or variable snowpack.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Loose Dry
The bond between the new snow and older facetted snow may take a few days to strengthen. Expect loose dry avalanches in steep terrain to run fast and far.
- Be careful of loose dry power sluffing in steep, confined or exposed terrain.
- Use caution above cliffs and terrain traps where small slab avalanches may have severe consequences.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 19th, 2021 4:00PM
