Avalanche Forecast

Issued: Mar 17th, 2017 4:00PM

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

stephen holeczi, Parks Canada

Banff Yoho Kootenay.

Another storm on the way which will keep the danger ratings elevated through the weekend. Avoid avalanche terrain.

Summary

Weather Forecast

Another pulse of snow coming through Saturday although forecast amounts have shrunk somewhat. Expect 20 to 30cm with moderate to strong alpine winds and freezing levels to 2000m. This means rain will fall at lower elevations. On Sunday precipitation will taper off with moderate alpine winds and temperatures will drop off to -15 to 18C.

Snowpack Summary

30-60cm of recent storm snow and wind have built significant load over a fundamentally weak snowpack. The mix of previous rain, warm temperatures, and this new snow is overloading buried storm and windslabs, as well as the weak basal facet layers. Cooling Friday helped curb natural activity, but only slightly

Avalanche Summary

A flight up Hwy. 93N today showed the extent of the avalanche carnage up to size 4 on all aspects and elevations. Some fracture lines are over 1km wide. Explosive control at the ski hills and on Hwy 93 South produced large results up to size 3.5 stepping down to the deep Dec. facets or the ground showing it is still extremely sensitive out there.

Confidence

Problems

Deep Persistent Slabs

The entire snowpack is built upon a structurally weak base, which has been overloaded by new snow and previous rain. This problem will remain touchy with the next incoming storm Saturday.

Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

3 - 4

Wind Slabs

Wind slabs over 1m deep exist at higher elevations, and in wind effected areas near treeline. This slab reacts easily to tests and continues to produce avalanches

Be aware of the potential for wide propagations.

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

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

2 - 3

Loose Wet

With freezing levels to 2000m Friday, loose, wet avalanches can't be ruled out. Steep, cliffed terrain and gullies will be likely areas.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Mar 18th, 2017 4:00PM