Avalanche Forecast

Issued: Mar 8th, 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.

stephen holeczi, Parks Canada

Banff Yoho Kootenay.

Avalanche control on Mt Stephen and Mt. Field in Yoho and Mt. Hector, on Hwy 93N Thursday, Mar 9. No activities in these areas during that day.

Summary

Weather Forecast

Light winds and -10C at treeline with only a trace of snow for Thursday. Friday another pulse of snow (10-12mm) along the divide and increased alpine winds into the moderate to strong range.

Snowpack Summary

50-60cm of storm snow has developed into a 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 only near ridge crests as of Wednesday.

Avalanche Summary

Over the last few days there have been many larger than expected avalanches to size 3 within the storm snow from avalanche control as well as naturals. Some have been seen to step down to the deeper weak layers.

Confidence

Due to the number of field observations

Problems

Storm Slabs

A 50 - 60 cm slab of storm snow continues to be reactive and is widespread at upper elevations. 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.

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

Expected Size

2 - 3

Valid until: Mar 9th, 2017 4:00PM