Avalanche Forecast

Issued: Mar 16th, 2016 4:00PM

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

Ian Jackson, Parks Canada

Banff Yoho Kootenay.

Pay attention to solar warming as the sun comes out over the next few days. Lots of big avalanches have been triggered with avalanche control showing that the deeper layers are still active.

Summary

Weather Forecast

Clearing skies in the forecast starting on Thursday. This should bring about a more spring-like diurnal pattern of daytime warming on solar aspects and cold overnight temperatures. Winds should be light throughout the period.

Snowpack Summary

The snowpack is complex right now. 30-70 cm of new snow sits on crusts below 1800m and on W through E aspects into the alpine. This has been reactive with explosives in many areas recently. On polar aspects, the new snow is bonding better, but the lower snowpack is still facetted and weak, with many avalanches stepping down to near the ground.

Avalanche Summary

More avalanche control today on the sunshine road produced numerous large avalanches stepping down to ground on 5 of 8 shots. These were in thin, windloaded alpine areas on all aspects and show that the deeper weak layers are still reactive. Additionally, cornices were large and easily triggered.

Confidence

Due to the number of field observations on Wednesday

Problems

Deep Persistent Slabs

The mid-pack facets remain weak, especially in thin or rocky areas. Avoid steep or unsupported terrain, and watch for signs of instability such as whumpfing and cracking.

Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Persistent Slabs

Now that the sun is higher in the sky, buried suncrust becomes more of a problem. Presently there are several crusts buried on S through E aspects, with 30-70 cm overlying them. This problem is most significant in the south Kootenay region.

Dig down to find and test weak layers before committing to a line.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Cornices

Cornices are large and fragile right now. Numerous have been triggered by explosives and skiiers in the last few days and have triggered slabs on the slopes below. Heads up as the sun destabilizes them further over the next few days.

Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.Give cornices a wide berth when travelling on or below ridges.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Mar 17th, 2016 4:00PM