Avalanche Forecast
Issued: Dec 23rd, 2019 3:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Storm Slabs.
cgarritty,
Avalanche Canada
Very dangerous avalanche conditions exist in the South Coast Inland - particularly in the north of the region. This is a time for very conservative terrain selection and the avoidance of most avalanche terrain at higher elevations.
Summary
Confidence
Moderate -
Weather Forecast
Monday night: Becoming cloudy. Isolated flurries in the south of the region. Light southwest winds.
Tuesday: Cloudy with isolated flurries in the north of the region, continuing overnight. Light southwest winds. Alpine high temperatures around -8.
Wednesday: Mainly cloudy, with cloud decreasing.Light northeast winds. Alpine high temperatures around -8, closer to -6 in the south of the region.
Thursday: A mix of sun and cloud. Light to moderate southwest winds. Alpine high temperatures around -7.
Avalanche Summary
A widespread avalanche cycle was observed across the region on Friday and Saturday. Avalanches were reported to be running to valley-bottom in the north of the region, failing on the weak layer described in the snowpack summary below.
Human-triggered avalanches are expected to be very likely to occur on Tuesday at higher elevations, particularly in the northern half of the region (e.g., Duffey, Hurley, etc.). See this MIN report of an avalanche involvement on Monday for an example of the issue at hand.
Given our current snowpack structure, we recommend avoidance of alpine avalanche terrain and very conservative decision-making at treeline.
Snowpack Summary
Over 120 cm of snow accumulated in the south of the region with the recent storm and over 40 cm in the north of the region. The snow fell with strong southwest wind. This snow is likely gaining strength as the days pass but still has the possibility of being triggered by a person or machine.
Depending on your location, the above-mentioned storm snow may be straining a now deeply buried weak layer composed of sugary faceted grains and hard melt-freeze crust from mid-November. This structure is a recipe for large and destructive avalanches and a problem that may persist for weeks to months. The layer certainly exists in the north of the region but it is uncertain to what degree it is a problem in the south of the region.
Terrain and Travel
- Travel in alpine terrain is not recommended.
- Don't let the desire for deep powder pull you into high consequence terrain.
- Persistent slabs have potential to pull back to lower angle terrain.
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
Problems
Persistent Slabs
A touchy weak layer is buried in the snowpack, which has recently produced large and destructive avalanches that have travelled far. There is uncertainty on the spatial distribution of the layer and whether it will remain a concern in the distant future. Until more evidence exists, it is prudent to assume the layer is present and capable of forming large, destructive avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Storm Slabs
Storm slabs formed during the weekend's storm may remain reactive to human traffic. With the substantial amount of snow that fell, it may take more time than usual for the snow to stabilize. If triggered, storm slab avalanches may step down to a deeply buried weak layer, forming very destructive avalanches that could travel far.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 24th, 2019 5:00PM
