Avalanche Forecast

Issued: Mar 24th, 2017 4:00PM

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

ian jackson, Parks Canada

Banff Yoho Kootenay.

While human triggering is likely at treeline and above, it is still essential to manage your exposure to avalanche terrain at lower elevations: natural avalanches reaching valley bottom trails are still considered possible.

Summary

Weather Forecast

Expect 5 to 10 cm to arrive starting Friday night through Saturday as winds shift from South back to West and climb into the moderate range. Temperatures will cool to -15C values in the ALP Sunday morning with some clearing expected before the cycle repeats: winds shift back to a light South flow bringing warming and a bit more precip for Monday.

Snowpack Summary

100cm of dense, rounded snow comprises the upper half of the snowpack and sits on a very weak base of depth hoar. This unstable structure produces consistent, sudden collapse test results in the depth hoar layer approximately 60cm from ground. Two shears persist near the surface down 15 and 35cm indicating lingering instability in the storm snow.

Avalanche Summary

The natural activity has begun to diminish over the last few days however daily reports of activity continue to come in with a sz 2.5 reported on the NE aspect of Mt Fatigue today. It appears to take only very small inputs of sun, wind or precip to trigger natural events and artificial / human triggering should be considered likely.

Confidence

Intensity of incoming weather systems is uncertain on Friday

Problems

Deep Persistent Slabs

Natural activity is starting to taper, but the snowpack is considered very suspect right now. Large avalanches initiating TL and above have recently run to valley bottom with crowns up to 2m + deep and several hundred meters in length.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.Be wary of slopes that did not previously avalanche.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 4

Wind Slabs

Wind transport was significant Thursday and has continued to a lesser extent Friday. Expect the fresh slabs that have formed at higher elevations to be easy to trigger. Expect the new growth on cornices to be fragile.

Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

2 - 3

Valid until: Mar 25th, 2017 4:00PM