Avalanche Forecast

Issued: Mar 7th, 2017 4:00PM

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

william lawson, Parks Canada

Banff Yoho Kootenay.

The storm slab continue's to be reactive, producing large avalanches and remote slab releases.

Summary

Weather Forecast

A pulse of precipitation is expected tonight with 5 to10cm and moderate winds from the west, temperatures will remain below freezing with lows in the -20's. No significant low pressure systems are expected this week, but expect small convective pulses to bring in some snow.

Snowpack Summary

40-50cm of storm snow has developed into a touchy storm slab that is sensitive to triggers at treeline and above. This sits over a supportive mid-pack, with the lower half of the snowpack consisting of weak facets and depth hoar. There is isolated wind effect near ridge crests only; the notable observation is the lack of wind effect.

Avalanche Summary

Avalanche control on Mt Whymper and Mt Simpson today. On Whymper results were similar to previous control this week, touchy storm slabs producing avalanches to size 3 as well as remote avalanches on adjacent slopes. Further south at Mt Simpson results were less dramatic, mostly smaller soft slab releases with one size 2.5 from a cornice release.

Confidence

Problems

Storm Slabs

A 50 cm slab of storm snow continues to be reactive. Avoid any avalanche starting zones, as this slab appears to be widespread. Fracture lines have been spreading into adjacent terrain, so mind your exposure carefully.

Be aware of the potential for wide propagations.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Deep Persistent Slabs

The entire upper half of the snowpack overlies a structurally weak base. Avoid thin parts of a slope or rocky outcrops at tree line and above. where triggering of this problem is most likely.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Mar 8th, 2017 4:00PM