Avalanche Forecast
Issued: Feb 7th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
ahanna,
Avalanche Canada
At upper elevations, touchy wind slabs are the main concern. While around treeline, a weak layer of surface hoar continues to produce large avalanches in response to human triggers. Stick to low angle slopes and treat open glades and leeward terrain features as suspect.
Summary
Confidence
Weather Forecast
Sunday night: Partly cloudy, light northwest ridgetop wind, alpine temperature -12.
Monday: Sunny, light to moderate northwest ridgetop wind, alpine high -17.
Tuesday: Sunny, light northerly ridgetop wind, alpine high -20.
Wednesday: Sunny, light northerly ridgetop wind, alpine high -23.
Avalanche Summary
A natural storm slab cycle up to size 2, as well as explosive and skier controlled storm slabs to size 1.5 were observed in the southeast of the region on Saturday.
Several skier triggered persistent slab avalanches have been reported in the last few days. They have generally been large (size 2-3) with wide propagation, at elevations around treeline (1800-2000 m) where the persistent layer exists as surface hoar.
Last week, a size 3.5 was reported to have failed on a crust that was buried in early December. A smaller avalanche stepped down to this deeper layer, resulting in a very large and destructive avalanche.
Snowpack Summary
30-60 cm of recent snow may sit on a weak layer which exists as a freezing rain crust in some areas and surface hoar in others.. It is not known how widespread this layer is, but it may have the potential to produce avalanches where it exists.
There is now about 50-80 cm of recent snow sitting above a widespread persistent weak layer that consists of facets in some areas, a melt-freeze crust in many areas, on a sun crust on steep south-facing slopes, and large surface hoar in sheltered areas. This layer has been the most reactive at treeline and below treeline, where it exists as surface hoar.
There are potentially several more layers of surface hoar in the upper snowpack, with the most notable one down about 80-120 cm. This layer was buried in early January.
A crust surrounded by weak faceted grains is buried deep within the snowpack. It may be possible to trigger this layers with a large load.
Terrain and Travel
- Use conservative route selection and resist venturing out into complex terrain.
- Keep in mind that human triggering potential persists as natural avalanching tapers off.
- Be careful as you transition into wind affected terrain.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
Problems
Wind Slabs
Recent wind from southwest to northwest has blown recent snow into wind slabs in lee features at upper elevations.
In wind sheltered areas, low density storm snow may be prone to sluffing especially with skier traffic.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
50-80 cm of snow sits on a persistent weak layer that was buried near the end of January. This layer consists of a melt-freeze crust in some areas, surface hoar in sheltered areas, and facets in some areas. This layer has been the most reactive at treeline, where it exists as surface hoar.
Another layer of surface hoar that was buried in mid-January may still be possible to trigger, and it is now down about 80-100 cm.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 8th, 2021 4:00PM
