Avalanche Forecast
Issued: Jan 9th, 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
Watch for wind slabs that may remain sensitive to human triggers and keep in mind the lingering potential for large and destructive persistent slab avalanches.
Summary
Confidence
Weather Forecast
Saturday night: Partly cloudy, strong south wind, freezing level valley bottom.
Sunday: Flurries, up to 5 cm, strong southwest wind, alpine high -7, freezing level 1100 m.
Monday: Flurries, up to 5 cm, strong southwest wind, alpine high -6, freezing level 1200 m.
Tuesday: Snow, 5-10 cm, strong southwest wind, alpine high -5, freezing level 1200 m.
Avalanche Summary
We have had a few recent reports of natural wind slab avalanches size 1-2 out of steep alpine terrain on north to east aspects. Wind slabs likely remain triggerable under human loads.
Although the persistent slab problem is trending towards being less reactive, the possibility of triggering it remains, and these avalanches would likely be large.
Field observations in this region are limited. If you get out, please consider submitting your observations to the Mountain Information Network.
Snowpack Summary
Severely wind affected surfaces can be found at upper elevation and in northern parts of the region, all the way down to treeline. 20-50 cm of snow sits on a spotty weak layer of surface hoar in many areas treeline and below. Rising freezing levels may promote slab development in the overlying snow, activating this weak layer on Sunday.
A persistent weak layer is now buried 70-100 cm below the surface. The distribution of this layer is variable and it can present as surface hoar and/or a crust. It has been reported as most prevalent in areas near Valemount.
There is a prominent crust near the base of the snowpack. This crust likely has weak facets above and/or below it. There have been no recent avalanches reported on this layer, but would be most likely to trigger in steep, shallow, rocky terrain, where the snowpack transitions from thin to thick over a short distance.
Terrain and Travel
- Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
- Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
- Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Problems
Wind Slabs
Previous snow and wind have created deep pockets of wind slab in lee terrain features at upper elevations. These were very reactive before the weekend and may remain sensitive to human triggers.
Any soft snow that remains available for transport will likely be blown into fresh, reactive wind slabs by strong winds Sunday.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
There are two persistent weak layers of concern within the snowpack. The shallower one consists of surface hoar and is down around 20-60 cm. At this depth, it remains triggerable by humans.
The second layer is more variable but consists mainly of a crust and/or surface hoar down 70-100 cm. This layer has been found to be most prevalent at and below treeline in areas near Valemount.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Valid until: Jan 10th, 2021 4:00PM
