Avalanche Forecast
Issued: Dec 24th, 2019 3:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
cgarritty,
Avalanche Canada
A serious persistent slab problem is dominating avalanche concerns in the north of the region. Danger in the south of the region is MODERATE and should be limited to wind slabs lingering on leeward features near ridgetop.
Summary
Confidence
Moderate -
Weather Forecast
Tuesday night: Cloudy. Light southwest winds.
Wednesday: A mix of sun and cloud, clearer in the north of the region. Isolated flurries bringing a trace of new snow in the south. Light northeast winds. Alpine high temperatures around -7, closer to -6 in the south of the region.
Thursday: Mainly cloudy with scattered flurries developing late in the day and bringing up to 5 cm of new snow by morning. Light to moderate southwest winds, becoming strong at ridgetop. Alpine high temperatures around -8
Friday: Mainly cloudy with lingering isolated flurries and a trace of new snow. Light to moderate southwest winds. Alpine high temperatures around -7, closer to -5 in the south of the region.
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 remain likely to occur on Tuesday at higher elevations, but mainly 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 very conservative route-finding and decision making in higher elevation avalanche terrain in the north of the region.
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 snowpack conditions found beneath this layer are variable over the region and in some areas highly problematic.
In the north of the region, the above-mentioned storm snow has brought a critical load to 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. This problematic layer is largely absent in the south of the region.
Terrain and Travel
- 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.
- Avoid steep convexities or areas with a thin, rocky, or variable snowpack.
- Carefully evaluate steep lines for wind slabs.
Problems
Persistent Slabs
A touchy weak layer is buried in the snowpack in the north of the region. This layer has recently produced large and destructive avalanches that have travelled far. This problem is largely absent in the south of the region.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Wind Slabs
Persistent slabs may not be a concern in the south of the region, but a cautious snowpack evaluation is still warranted at higher elevations where recent snow has been redistributed into wind slabs in leeward terrain near ridgetop.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 25th, 2019 5:00PM
