Avalanche Forecast
Issued: Dec 21st, 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
Substantial snowfall triggered avalanche cycles on Friday and Saturday. This snow will likely remain touchy to human traffic and it has loaded buried weak layers that will need time to stabilize. Best to avoid alpine avalanche terrain and travel conservatively below.
Summary
Confidence
Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.
Weather Forecast
SATURDAY NIGHT: Mostly cloudy, light southwest wind, alpine temperature -8 C, freezing level below valley bottom.
SUNDAY: Mix of sun and cloud, light southwest wind, alpine temperature -7 C, freezing level 600 m.
MONDAY: Mostly clear skies, light southwest wind, alpine temperature -7 C, freezing level below valley bottom.
TUESDAY: Mix of sun and cloud with isolated flurries, 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 and Saturday. Avalanches were reported to be running to valley-bottom in the north of the region.
Human-triggered avalanches are expected to be very likely to occur on Sunday, with the potential to fail in both the recent storm snow and potentially in the weak layers described in the Snowpack Summary. We recommend avoiding alpine avalanche terrain and to travel conservatively at and below treeline until the snowpack strengthens.
Snowpack Summary
Over 120 cm of snow has accumulated in the south of the region with this storm and over 40 cm in the north of the region. The snow fell with strong southwest wind. This snow may remain touchy to human traffic on Sunday.
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 may overly a weak layer of feathery surface hoar buried about 150 cm, in areas where the storm snow hasn't already caused it to fail.
Avalanches triggered in the storm snow could step down to these buried weak layers, producing large and destructive avalanches.
Terrain and Travel
- Travel in alpine terrain is not recommended.
- Don't let the desire for deep powder pull you into high consequence terrain.
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
Problems
Storm Slabs
Storm slabs formed during this latest storm are likely to remain touchy to human traffic. This snow will need some time to stabilize. 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
Persistent Slabs
A touchy weak layer is buried in the snowpack, which has recently been tested with rapid loading during the storm. There is uncertainty on whether the layer will remain a concern in the distant future. For now, it is prudent to assume the layer is still capable of being triggered and forming large, destructive avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 22nd, 2019 5:00PM
