Avalanche Forecast

Issued: Feb 1st, 2016 4:20PM

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

Conrad Janzen, Parks Canada

Banff Yoho Kootenay.

Potential still exists for human triggering of large avalanches. Manage overhead exposure carefully and make careful terrain choices at all elevations. We are back to a more typical Rockies snowpack and the weaknesses will be present for some time.

Summary

Weather Forecast

Continued cool temperatures (-12 to -18'C) through Wednesday with light West winds and very light flurries.

Snowpack Summary

Wind slabs in alpine and tree line areas. 30-60cm of snow over the Jan 6 surface hoar/facet/sun crust layer is reactive to skier triggering. Sudden collapse results on the Jan 6 and Dec 3 surface hoar layers down 55 and 85cm in the Kootenay region. Extensive whumphing on mid-pack facets and many very weak faceted areas today near Observation Peak.

Avalanche Summary

Visitor Safety was able to trigger a size 1.5 wind slab on a SE steep alpine feature on Monday near Observation Peak. A large natural cornice collapse also occurred Monday in the Sunshine backcountry on Quartz Ridge. Lots of evidence of the previous widespread natural avalanche cycle up to size 3 on all aspects with some very large propagations.

Confidence

Problems

Wind Slabs

Recent wind has built soft slabs 30 to 50cm deep in alpine and tree line lee areas, and established new growth on cornices. Although these slabs are slowly becoming more difficult to trigger, human triggering is still possible.

Avoid steep lee and cross-loaded featuresIf triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

30-60 cm of snow overlies the Jan 6 layer of surface hoar, facets and sun crust. Test results on this layer show it is still in the range of human triggering with potential for failures to step down into deeper layers and result in large avalanches.

Avoid open slopes and convex rolls where buried surface hoar may be preserved.Use careful route-finding and stick to moderate slope angles with low consequences

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3

Valid until: Feb 2nd, 2016 4:00PM