Avalanche Forecast

Issued: Mar 19th, 2017 5:24PM

The alpine rating is high, the treeline rating is high, and the below treeline rating is considerable. Known problems include Deep Persistent Slabs, Wind Slabs and Loose Wet.

tim haggarty, Parks Canada

Banff Yoho Kootenay.

Avoid exposure to avalanche terrain: large avalanches can reach valley bottom trails. Although activity should taper in the wake of this weekend's storm, as the sun comes out Monday it would be wise to watch what happens from a distance.

Summary

Weather Forecast

A ridge has established itself over British Columbia in the wake this weekend's storm and as this pushes into the region clearing will result, even if briefly, Sunday night. Despite a return to -10C temperatures at treeline through Monday night, expect solar inputs to be significant before freezing levels climb back up to 1800m late Tuesday.

Snowpack Summary

15 to 30cm of storm snow combined with moderate to strong S and W winds this weekend have built superficial wind and storm slabs. This new load combined with 40 to 80 cm of snow that has fallen in the last two weeks continues to overload the deep basal facet layers in all corners of the region. Rain to 2200m Saturday created moist to wet snow.

Avalanche Summary

New evidence of Natural activity has been observed today on patrols around the park and explosive control work has produced massive results in the Lake Louise and Yoho regions with impressive propagation. Large avalanches that initiate in the alpine and at treeline continue to entrain moist snow BTL attaining large destructive potential and reach.

Confidence

Timing or intensity of solar radiation is uncertain on Monday

Problems

Deep Persistent Slabs

The entire snowpack is built upon a structurally weak base, which has been overloaded by new snow and previous rain. Large avalanches are reaching historical run outs and crossing cross country ski trails.

Be wary of slopes that did not previously avalanche.Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

3 - 4

Wind Slabs

Wind slabs over 1m deep exist at higher elevations, and in wind affected areas near treeline. This slab reacts easily to tests and continues to produce avalanches. Correspondingly, cornices have grown significantly and are fragile.

Be aware of the potential for wide propagations.Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 3

Loose Wet

With freezing levels in excess of 2200m Saturday, the snowpack at lower elevations lost strength. As this snow refreezes, moist snow remains under surface crusts which large avalanches from upper elevations can entrain to reach surprising distances.

Use extra caution on slopes if the snow is moist or wet.Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Valid until: Mar 20th, 2017 4:00PM