Avalanche Forecast
Issued: Dec 21st, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
swerner,
Avalanche Canada
Give the snowpack time to adjust to recent loading, especially in open areas where snow may have been wind stiffened. Avalanche activity, cracking, whumphing and stiff snow are signs of instability.
Summary
Confidence
Moderate - Confidence is due to a stable weather pattern with little change expected.
Weather Forecast
The lull before the next storm. This region can expect some light precipitation as a weak trough crosses the north. Â
Tuesday: Mostly cloudy with some flurries. Alpine temperatures near -6 with light wind from the South. Freezing levels valley bottom.
Wednesday: Arrival of next storm. Snow amounts 10-20 cm. Alpine temperatures near -4 and ridgetop winds moderate from the South. Freezing levels 600 m.
Thursday: Snow 20-30 cm with a strong southwest wind. Freezing levels 600 m.
Avalanche Summary
On Monday a few natural avalanches up to size 2 were reported near Terrace. Also, explosives control work triggered a few size 2 avalanches. I suspect natural avalanche activity will taper off tomorrow but human triggered avalanches remain likely.
On Sunday there were reports of shooting cracks in convex (roll over) type features. Explosive triggered storm slabs up to size 2 and a few natural loose dry avalanches up to size 1 from steep and unsupported terrain.Â
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Snowpack Summary
Some areas have seen upwards of a meter of new snow in the past week. Storm slabs may continue to reactive to human triggering especially where the snow has been stiffened by wind.
A crust that was buried in early December is now down 80-120 cm in the alpine but is closer to the surface at and below treeline elevations. Around this crust are facets and potentially surface hoar in sheltered areas. Storm slabs may step down to this layer.
The early-November crust is buried around 100-200 cm at treeline. This crust may have weak and sugary facets above it in parts of the region. Uncertainty remains about where this layer remains a problem in the region, but it may be localized to the northern half of the region.
Terrain and Travel
- Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
- 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.
- Don't let the desire for deep powder pull you into high consequence terrain.
Problems
Storm Slabs
Storm slabs may continue to be reactive to human triggers. On open slopes in the alpine and treeline this may present more like a windslab problem, but even in more sheltered zones the snow needs some more time to adjust to recent loads.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A crust that was buried in early December is now down 80-120 cm in the alpine but is closer to the surface at and below treeline elevations. Around this crust are facets and potentially surface hoar in sheltered areas. Human triggered avalanches and storm slabs may step down to this layer.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 22nd, 2020 4:00PM
