Avalanche Forecast

Issued: Mar 26th, 2016 4:00PM

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

stephen holeczi, Parks Canada

Banff Yoho Kootenay.

http://www.pc.gc.ca/apps/links/goto_e.asp?destination=Heads Up! A Special Avalanche Warning is in effect as we do not think the danger rating of MODERATE adequately illustrates the complexity in the snowpack right now. This is a low probability, high consequence period with a highly variable snowpack.

Summary

Weather Forecast

Sunday will see light SW winds,Â a decent overnight freeze and freezing levels up to 1900m.Â Sunday night into Monday a NE flow is forecasting 15-20 cm in the Sunshine region with half that expected in Lake Louise.

Snowpack Summary

A thin melt/freeze crust exists on solar aspects, and on shady aspects up to 2000m where it disappears. Dry snow exists mainly on N aspects only. Shallow snowpack areas are weak, and we are concerned about facets in the lower snowpack overlain by a stiff slab which produces easy, sudden collapses in tests.

Avalanche Summary

Over the past week there have been large avalanches triggered by cornice failures, explosives and people on the deep persistent layer. Activity has tapered off in the last few days. Some loose wet avalanches noted on solar aspects over the last 24 hours to size 2 along Hwy 93 N. One slide observed pulled out a deeper slab in steep terrain.

Confidence

Forecast snowfall amounts are uncertain on Monday

Problems

Deep Persistent Slabs

Deep facet layers remain very weak, especially in thin or rocky areas. Avoid large open slopes, steep slopes (>30 degrees) and be wary that you can trigger this problem from a long distance away - the slab is stiff and it propagates far.

Avoid steep convexities or areas with a thin or variable snowpack.Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 4

Cornices

Cornices are large, and warm temperatures make them weak. Ensure you give them a wide berth on ridge crests, as they can pull back a long way when they fail and may trigger avalanches below. If you need to travel under cornices - move quickly.

Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 3

Loose Wet

This problem should only exist in the afternoon near the valley bottom elevations (below 1500m), and will start once the day has warmed up and the snow at low elevations turns to slush. Ice climbers should avoid low elevation gullies.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Mar 27th, 2016 4:00PM