Avalanche Forecast
Issued: Dec 19th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
mconlan,
Avalanche Canada
Snow and strong wind will form new slabs and continue to load an already touchy snowpack. An avalanche cycle may occur during Saturday night's storm and humans will surely be capable of triggering avalanches on Sunday.
Summary
Confidence
Moderate - Forecast precipitation (either snow or rain) amounts are uncertain.
Weather Forecast
SATURDAY NIGHT: Snow, accumulation 15 to 25 cm, 60 to 80 km/h southwest wind, alpine temperature -5 C, freezing level 1200 m.
SUNDAY: Morning snowfall then clearing, accumulation 5 cm, 40 to 60 km/h northwest wind, alpine temperature -4 C, freezing level 1500 m.
MONDAY: Snow, accumulation 15 cm, 20 to 30 km/h south wind, alpine temperature -7 C.
TUESDAY: Snow then clearing, accumulation 20 cm, 10 to 20 km/h northwest wind, alpine temperature -6 C.
Avalanche Summary
There have been many human-triggered avalanches from the past few days, often within the weak layer described in the snowpack summary. Riders have been reporting conditions as "unsettling', 'electric', 'super touchy', and 'running far'. Avalanches appear to have been reported on all aspects and at all elevation bands.
Avalanche activity is expected to continue on Sunday as new slabs are formed and the snow further loads the weak layers.
Snowpack Summary
Saturday night's snowfall will accumulate with strong southwest wind, forming wind slabs in exposed terrain. These will overly previous storm layers within the top 40 cm of the snowpack.
This snow will continue to load a weak layer around 30 to 60 cm deep. The layer may be composed of feathery surface hoar or sugary faceted grains and they overly a hard melt-freeze crust. Riders have reported avalanche activity and whumpfing on this layer as well as surprising snowpack test results. This layer remains a major concern, as humans may be able to trigger large and destructive avalanches on it.
Another crust with associated faceted grains may be found near the base of the snowpack. There have been no recent avalanches reported on this layer but it remains on our radar. The most likely place to trigger it would be from shallow, rocky terrain.Â
Terrain and Travel
- Travel in alpine terrain is not recommended.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
Problems
Persistent Slabs
A weak layer of surface hoar and/or faceted grains overly a hard melt-freeze crust around 30 to 60 cm deep. The likelihood of triggering this layer is expected to be elevated on Sunday due to more snow load. Riders have triggered large avalanches on this layer, and the consequence of doing so will only increase as it gets deeper.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
More snow is expected Saturday night into Sunday morning, with strong southwest wind. Use particular caution immediately adjacent to ridges, where the slabs will likely be thickest and touchiest. The storm snow may also be touchy in sheltered terrain features, so check for the bond of the snow prior to committing to avalanche terrain.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 20th, 2020 4:00PM
