Avalanche Forecast

Issued: Mar 25th, 2017 3:47PM

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

Avalanche Canada mgrist, Avalanche Canada

With the new snow load, persistent slab problems continue to rear their ugly head, so conservative terrain use is essential. Stay aware of overhead hazards.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

We'll have a brief lull in the action on Sunday before things pick up again Monday afternoon into Tuesday. Winter's not done yet! SUNDAY: Lingering flurries, moderate southeast wind, freezing levels 900m, alpine temperature around -5 C. MONDAY: Snow in the afternoon (10cm). Strong south wind, freezing level around 1100 m with alpine temperature around -3 C. TUESDAY: 15-25 cm possible Monday overnight into Tuesday afternoon, strong south wind, freezing levels 1100m.

Avalanche Summary

On Friday, a spooky Size 3.5 persistent slab with impressive propagation was remote-triggered north of Terrace at 1500m elevation. See here for more details in this excellent post.Also on Friday, a Size 2.5 persistent slab (2m deep) was reported running out of steep terrain. On Thursday, skiers were able to trigger a small Size 1 wind slab (10cm thick), running on the March 22nd surface hoar layer.Reports from Tuesday indicate the persistent slab problem is alive throughout the region. A few natural size 2-2.5 avalanches were triggered in the Bear Pass / Stewart area by solar input and cornices. A skier also remotely triggered a size 2 avalanche on the February facet/crust interface on a moraine feature around 1150 m (40 cm deep). Similar activity was reported the previous day, including a size 3 avalanche that was remotely triggered from flat terrain by a snowmobiler north of Stewart.In addition to the daunting persistent slab problem, the incoming weather pattern is looking to continually build fresh storm slabs.

Snowpack Summary

Fresh storm slabs and cornices are forming in the lee of exposed terrain as yet another March storm has brought 5-15cm of new snow (20cm near Stewart) and moderate southwest winds. This recent snow sits on a crust on solar aspects and below 1000 m.Snow may still be poorly bonded to a 40 cm deep crust and surface hoar interface from mid-March, however, the late-February interface has been the more troublesome persistent layer. It's composed of facets, crust, and surface hoar roughly 70-140 cm deep and is still reactive throughout the region, especially in shallower areas around Stewart and Bear Pass.

Problems

Storm Slabs

An icon showing Storm Slabs
New snow may overload wind slabs sitting on the March 22nd surface hoar layer. Conservative terrain use is essential and manage your overhead exposure.
The new snow will require several days to settle and stabilize.Be aware of the potential for wide propagations due to the presence of underlying windslabs.If triggered, the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
A weak facet/crust layer from late February has produced several large human triggered avalanches the past few days. Triggering this layer is most likely in shallower areas, but a small wind slab or cornice fall could act as a natural trigger.
Remote triggering is a concern, watch out for adjacent slopes.Use conservative route selection, choose moderate angled and supported terrain with low consequence.Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 4

Valid until: Mar 26th, 2017 2:00PM