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Avalanche Forecast

Mar 9th, 2017–Mar 10th, 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
4: High
The avalanche danger rating in the alpine will be high
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.

It's time to dial back terrain choices at all elevation bands. A buried persistent weak layer has created the potential for surprisingly large avalanches.

Confidence

High -

Weather Forecast

Friday: Mainly clear skies / Moderate easterly winds / Alpine temperature of -15Saturday: Overcast skies with light flurries / Moderate easterly winds / Alpine temperature of -12Sunday: 15-30cm of new snow / Moderate southerly winds / Alpine temperature of -5

Avalanche Summary

On Monday two avalanches were simultaneously remotey-triggered below treeline west of Terrace. See here for the excellent details in the Facebook post. We had reports of two rider-triggered wind slab avalanches (Size 1.5 and 2.0) southwest of Terrace on Sunday. In both cases the crown height was 50cm and shooting cracks were also reported in mellow terrain. There was a remote-triggered Size 1 in the Shames backcountry, also with a 50cm crown, running on a weak facet layer.  These avalanches speak to the touchy persistent avalanche problem in the region.Strong winds on Thursday should promote a new round of wind slab activity. The persistent slab problem is expected to remain touchy as the recent storm snow settles into a cohesive slab over top of the late February persistent weak layer.

Snowpack Summary

On Tuesday night the region received between 5-40cm of new snow with the greatest accumulations occurring in the south of the region. Southwest winds and more recent easterly winds are expected to have redistributed this new snow forming fresh wind slabs on a variety of aspects. 70-150 cm below the surface you'll find a variety of old surfaces which were buried in late February. These weak surfaces, which remain the primary concern in the region, include surface hoar, facets, stiff wind slabs and a melt-freeze crust below 1600 m. The overlying slab remains reactive on this interface, with ongoing reports of whumpfing in flat terrain. Moreover, we've had reports of sudden, propagation-likely test results on this layer. Below this interface the snowpack is generally settled and strong, with the exception being shallow snowpack areas around Bear Pass and Ningunsaw where basal facets remain an ongoing concern.

Avalanche Problems

Persistent Slabs

A mix of persistent weak crystals lurk up to 150cm below the surface, and have the potential for surprisingly large avalanches. Conservative terrain selection remains critical for the foreseeable future.
Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 3

Wind Slabs

Recent snow accumulations are expected to have been shifted into fresh wind slabs in exposed lee terrain. These surface instabilities have the potential to step-down to deep, more destructive layers.
If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 2