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Archived

Avalanche Forecast

Mar 25th, 2017–Mar 26th, 2017
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Northwest Coastal.

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.

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.

Avalanche Problems

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

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