Avalanche Forecast

Issued: Jan 12th, 2018 4:00PM

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

stephen holeczi, Parks Canada

Little Yoho.

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.

Summary

Weather Forecast

A warming trend on Saturday in Little Yoho with temperatures in the -5C range. There will be increased Westerly winds with alpine gusts in the 50-80kmh range and only a couple cm of new snow. The warmer temperatures will continue Sunday.

Snowpack Summary

30-45 cm of low density snow has fallen over the past 5 days with wind effect limited to alpine ridges or the Kicking Horse Pass area (Yoho Blow) where isolated windslabs exist. There is now 30-60 cm overlying the Dec 15 persistent weak layer which is becoming reactive at treeline and below with widespread whumphing observed.

Avalanche Summary

Numerous windslab avalanches up to size 2 were observed to have run during the last storm, mainly near ridge crests or under rock bands where spindrift has accumulated. One size 2 persistent slab was observed near the back of Emerald Lake that failed on the Dec 15 surface hoar.

Confidence

Problems

Persistent Slabs

There is a dangerous weak layer down 30-60 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.

Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.

Aspects: All aspects.

Elevations: All elevations.

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