Avalanche Forecast

Issued: Jan 12th, 2018 4:00PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Persistent Slabs and Wind Slabs.

stephen holeczi, Parks Canada

Banff Yoho Kootenay.

The snowpack has almost reached tipping point with 40cm of soft snow overlying the Dec. 15 weak layer (surface hoar & facets). Warming temperatures and wind this weekend could push it over the edge at treeline and above.

Summary

Weather Forecast

A warmup is expected starting Saturday with alpine temps in the -3 to 5C range on the Eastern end of the range. Increasing Westerly winds will accompany this and we could see alpine elevation gusts in the 50-80kmh range by the evening with a couple cm of snow. It looks warm through the coming weekend.

Snowpack Summary

30cm snow has fallen over the past week with limited wind effect except near ridge crests. There is now a total of 30-50 cm overlying the Dec.15 persistent weak layer of facets and some surface hoar which is becoming reactive at treeline and above. This layer is producing easy to moderate sudden collapse results. Click for an example from today.

Avalanche Summary

A solo backcountry skier triggered a size 2 avalanche on Richardson's Ridge yesterday outside the Lake Louise Ski Resort boundary - this was a treeline area with a shallow snowpack. As well, numerous small windslabs were observed to have run over the past 48 hours and there has been plenty of settlements being reported at treeline and above.

Confidence

Problems

Persistent Slabs

There is a dangerous weak layer down 30-40 cm but it needs a stiffer slab overlying it for the avalanche to occur. We are "almost" at that tipping point so be very careful with this layer and travel conservatively even if you observe no avalanches.

Choose conservative lines and watch for clues of instability.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Wind Slabs

Soft windslabs formed during the last storm exist near ridge crests and under cliff bands. Watch for the changing feel of the snow under your feet and be wary of areas with denser surface snow.

Use caution in lee areas. Recent wind loading has created wind slabs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Jan 13th, 2018 4:00PM