Avalanche Forecast
Issued: Feb 6th, 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.
astclair,
Avalanche Canada
Triggering large avalanches remains likely in wind-drifted snow or on open slopes with a buried weak layer near and below treeline. These conditions require careful assessment and cautious terrain selection.
Summary
Confidence
Weather Forecast
Saturday night: Partly cloudy, isolated flurries with trace accumulations, moderate northwest wind at ridgetop, alpine temperature dropping to -18 C.
Sunday: Mainly sunny, light northwest wind, alpine high temperature -20 C.
Monday: Mix of sun and cloud, light northwest wind, alpine high temperature -24 C.
Tuesday: Clear, light northwest wind, alpine high temperature -26 C.
Avalanche Summary
Three different flavors of avalanches can be expected on Sunday. Loose dry avalanches may be possible in areas where the recent snow has not formed a slab. Although typically small (size 1-1.5), these avalanches pose a serious concern for ice climbers and for people traveling in extreme terrain where the possibility of getting knocked off of your feet has severe consequences. At upper elevations, newly formed wind slabs are expected to be reactive to human triggering. At treeline elevations and below, avalanches may be remotely triggered and break larger than expected on a reactive layer of surface hoar. This MIN and this MIN are examples of natural avalanches propagating wider than usual due to this weak layer.
Note: We currently have very few observations from this region. Please consider sharing what you see by submitting a MIN report.
Snowpack Summary
Another 5 cm of snow overnight with strong winds from the northwest have formed fresh wind slabs in lee features at upper elevations. With up to 25 cm of low density snow from the past couple days, cohesion-less snow in sheltered areas may be prone to dry loose avalanches.
The snow from the past week is settling over a reactive weak layer of surface hoar buried 40-70 cm deep. This persistent weak layer has potential to surprise backcountry users with how wide the fracture can travel across slopes. Recent avalanches on this layer have primarily been reported at treeline and below. This layer will be slow to gain strength and requires careful terrain selection.
A second weak of layer of surface hoar from mid January is down around 70-110 cm and is most prevalent in sheltered, open slopes at treeline and below.
Deep persistent weak layers can still be found in the lower snowpack. These weak layers are most likely to be triggered from rocky areas with a shallow or thin to thick snowpack.
Terrain and Travel
- Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
- Stay off recently wind loaded slopes until they have had a chance to stabilize.
- Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.
Problems
Wind Slabs
Recent strong winds have redistributed the new snow into wind slabs on lee features at upper elevations that are likely to be human-triggered.
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A weak layer of surface hoar is buried 40-70cm on sheltered slopes near and below treeline. This layer is likely to be reactive to human triggers in specific areas.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Valid until: Feb 7th, 2021 4:00PM
