Avalanche Forecast

Issued: Feb 21st, 2017 4:13PM

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

grant statham, Parks Canada

Banff Yoho Kootenay.

Current conditions are some of the most dangerous for backcountry travelers. Natural avalanches are unlikely; thus the problem is not obvious - but human triggered avalanches are likely, and happening daily. Keep a wide margin of safety . . .

Summary

Weather Forecast

Temperatures falling overnight to reach -15 by Wednesday with highs around -10.Â Possibility of up to 10 cm of new snow on Wednesday, but this looks to be in eastern areas only. Return to sunny skies for Thursday.

Snowpack Summary

No new snow last 24-hr, but 25cm recent storm snow has formed isolated soft slabs near ridge crests in the alpine. Persistent problems remain with the lower half of the snowpack being weak and faceted especially in thin areas or near rocky outcrops. Cooler temperatures have helped to stabilize the snowpack below treeline but it is still very weak.

Avalanche Summary

Notable avalanches every day. A remotely triggered size 3 avalanche near Cirque peak on Sunday. On Monday, two large avalanches triggered by explosives in "the Elevator Shaft" at Lake Louise as well as a remote triggered size 2 in Kootenay Park. On Tuesday, skiers triggered a size 1.5 onto another group below in Lipalian 3 at Lake Louise.

Confidence

Problems

Deep Persistent Slabs

There is a thick slab over a structurally weak snowpack at all elevations. Likely areas of triggering are in thin parts of a slope or rocky outcrops at tree line and above where a failure can propagate to deeper areas and cause large avalanches.

Be aware of thin areas that may propogate to deeper instabilites.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 3

Wind Slabs

Small isolated new wind slabs are present in the alpine. Winds from several days ago have also created firm wind slabs which are now buried. Probe for these buried hard layers especially near ridge crests and in cross loaded features.

If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Feb 22nd, 2017 4:00PM