Avalanche Forecast
Issued: Feb 8th, 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
Brrrrrr! Cold and dry conditions persist under arctic air.
Monday night: Clear, light to moderate northwest ridgetop wind, alpine temperature -22.
Tuesday: Sunny, light northwest ridgetop wind, alpine high -19.
Wednesday: Sunny, light northwest ridgetop wind, alpine high -23.
Thursday: Sunny, light northeast ridgetop wind, alpine high -26.
Avalanche Summary
A natural storm slab cycle up to size 2 was observed Saturday. Explosive and skier controlled storm slabs to size 1.5 were produced through the weekend.
We are still receiving reports of persistent slab avalanches, triggered by skiers and explosives, generally large (size 2-3) with wide propagation, at elevations around treeline (1800-2000 m) where the persistent layer exists as surface hoar. Check out this great MIN describing a remotely triggered persistent slab avalanche in Kootenay Pass on Sunday.
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
Snow from the past week has seen some wind effect at upper elevations. It continues to settle over a reactive weak layer buried 60-80 cm deep. This persistent weak layer may exist as facets or a crust but it has been most reactive where it exists as large surface hoar crystals in sheltered areas treeline and below. Surface hoar has potential to surprise backcountry users with how widely the fracture can travel across slopes. This layer will be slow to gain strength and requires careful terrain selection.
Less reactive layers of surface hoar or facets buried in early January can be found down 100-160 cm.
The mid/lower snowpack is generally well settled and strong in most areas.
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.
Terrain and Travel
- Be careful as you transition into wind affected terrain.
- Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
- 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
60-80 cm of snow sits on a persistent weak layer that was buried near the end of January. 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 9th, 2021 4:00PM
