Avalanche Forecast
Issued: Dec 22nd, 2019 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Storm Slabs.
mconlan,
Avalanche Canada
Clear skies may lure you into bigger terrain, but this is not the time to expose yourself. The recent snow may remain touchy and it is resting on a weak layer in parts of the region. Read more here. Best to avoid alpine avalanche terrain and travel conservatively at treeline.
Summary
Confidence
Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.
Weather Forecast
SUNDAY NIGHT: Clear skies in the north of the region and cloudy with light snowfall in the south of the region, accumulation 2 to 5 cm, light northwest wind, alpine temperature -6 C, freezing level below valley bottom.
MONDAY: Mostly clear skies, light southwest wind, alpine temperature -7 C, freezing level below valley bottom.
TUESDAY: Mostly cloudy with isolated flurries, accumulation 1 to 3 cm, light southwest wind, alpine temperature -9 C, freezing level below valley bottom.
WEDNESDAY: Mostly cloudy with isolated flurries, accumulation 1 to 3 cm, light northwest wind, alpine temperature -8 C, freezing level below valley bottom.
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.
Human-triggered avalanches are expected to be very likely to occur on Monday at higher elevations, particularly in the northern half of the region (e.g., Duffey, Hurley, etc.). We recommend avoidance of alpine avalanche terrain and very conservative decision-making at treeline, given this weak snowpack.
Snowpack Summary
Over 120 cm of snow has 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 has the possibility of being triggered by human traffic.
The snow may be loading a weak layer of sugary faceted grains and hard melt-freeze crust buried mid-November, which 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 unclear whether 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 touchy to human traffic. With the substantial amount of snow that fell, it may take a bit more time for the snow to stabilize. If triggered, storm slab avalanches may step down to a buried weak layer, forming destructive avalanches that could travel far.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 23rd, 2019 5:00PM
