Avalanche Forecast

Issued: Mar 4th, 2017 4:29PM

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

conrad janzen, Parks Canada

Banff Yoho Kootenay.

Lots of new snow loading and natural avalanche activity today. Avoid terrain with overhead hazard and stick to moderate angled, supported terrain. Avalanche control is planned for Mt Bourgeau on Sunday. No climbing in this area on Sunday.

Summary

Weather Forecast

Precipitation will taper off on Saturday night but flurries will continue through Sunday with another 5cm expected to fall. Winds should become light to moderate out of the SW and temperatures are forecast to stay below freezing and relatively steady until Monday.

Snowpack Summary

20-40cm of new has fallen with Moderate to Strong SW winds. Lots of wind slabs are present above treeline with new cornice development. This large load of new snow sits on a supportive mid-pack, however the lower half of the snowpack consists of weak facets and depth hoar. Test results show regular failures in the weak facets in the Mod-Hard range.

Avalanche Summary

Poor visibility on Saturday, but natural, skier and explosive triggered avalanches were observed up to size 3 on all aspects running far down the paths. A skier remote size 3 occurred at 2300m on a SE aspect on Observation Peak failing on the Dec facets. Lots of sluffing in steep gullies was observed. Lots of whumphing in thin areas today as well!

Confidence

Due to the number of field observations

Problems

Wind Slabs

20-40cm of new snow and strong SW winds have forming fresh wind slabs and sensitive cornices above treeline. If these fail they could provide enough of a load to trigger deep persistent layers resulting in large avalanches.

Use caution in lee areas. Recent wind loading has created wind slabs.Pay attention to overhead hazards like cornices which could easily trigger deep slabs.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Deep Persistent Slabs

There is a thick slab over a structurally weak snowpack in most areas. Avoid thin parts of a slope or rocky outcrops at tree line and above. We are seeing increased natural activity as a result of the new snow including remote triggering.

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

Possible - Likely

Expected Size

2 - 3

Loose Dry

Watch for the new snow to fail easily in steep terrain. Use caution in confined features and around terrain traps such as cliffs and gullies.

Sluffs may trigger deeper instabilities.Be cautious of sluffing in steep terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Mar 5th, 2017 4:00PM