Avalanche Forecast
Issued: Dec 20th, 2019 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
mconlan,
Avalanche Canada
Over 100 cm of snow fell in the south of the region on Friday, over 30 cm in the north of the region, and more is on its way. Both natural and human triggering of avalanches will remain very likely on Saturday. Best to avoid avalanche terrain.
Summary
Confidence
Moderate - Uncertainty is due to the track & intensity of the incoming weather system.
Weather Forecast
FRIDAY NIGHT: Cloudy with snowfall, accumulation 10 cm in the north of the region and 20 cm in the south of the region, moderate to strong southwest wind, alpine temperature -5 C, freezing level 1000 m.
SATURDAY: Mix of sun and cloud in the north of the region and cloudy with snowfall in the south of the region, accumulation 10 to 15 cm, moderate southwest wind, alpine temperature -7 C, freezing level 1000 m.
SUNDAY: Mix of sun and cloud, light southwest wind, alpine temperature -7 C, freezing level 600 m.
MONDAY: Mix of sun and cloud, light southwest wind, alpine temperature -9 C, freezing level below valley bottom.
Avalanche Summary
A widespread avalanche cycle was observed across the region on Friday. Avalanches were reported to be running to valley-bottom in the north of the region. The cycle may continue into Friday night and Saturday, particularly in the south of the region where more snow is forecast.
Snowpack Summary
Over 100 cm of snow has accumulated in the south of the region with this storm and over 30 cm in the north of the region. The snow fell with strong southwest wind. More snow is expected in the south of the region on Friday night and Saturday while the skies dry up in the north. This snow will likely be very touchy and may produce both natural and skier-triggered avalanches on Saturday.
In the north of the region, the snow is 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.
In the south of the region, the snow is loading a weak layer of feathery surface hoar buried about 150 cm.
Avalanches triggered in the storm snow could step down to these buried weak layers, producing large and destructive avalanches.
Terrain and Travel
- Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
- Avoid exposure to overhead avalanche terrain, avalanches may run surprisingly far.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Problems
Storm Slabs
Substantial snowfall amounts have accumulated across the region and more snow is forecast for the southern half of the region into Saturday. An avalanche cycle may continue, with some avalanches reported as running to valley-bottom. Natural and human-triggered avalanches are very likely to occur on Saturday.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A touchy weak layer is buried in the snowpack, which has likely become more reactive with the substantial snow accumulation. This is an atypical snowpack for the region, which will require diligence until it strengthens. Avoidance of avalanche terrain is recommended for Saturday, as large and destructive avalanches may fail on this layer.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 21st, 2019 5:00PM
