Avalanche Forecast

Issued: Feb 24th, 2017 4:51PM

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

Avalanche Canada cgarritty, Avalanche Canada

Lingering wind slabs and the possibility of increasing persistent slab activity are keeping avalanche danger elevated in the region.

Summary

Confidence

Moderate -

Weather Forecast

Saturday: Mainly cloudy with isolated flurries bringing a trace to 5 cm of new snow, beginning in the afternoon. Winds moderate to strong from the southwest. Freezing level to 700 metres with alpine temperatures of -10 in the north of the region, closer to -6 in the south. Sunday: A mix of sun and cloud with isolated flurries and a trace of new snow. Winds light to moderate from the north. Freezing level to 500 metres with alpine temperatures of -10 in the north of the region, closer to 800 metres and -4 in the south. Monday: Mainly cloudy with isolated flurries and a trace of new snow. Winds light to moderate from the west. Freezing level to 400 metres with alpine temperatures of -11 in the north of the region, -7 in the south.

Avalanche Summary

A social media report from Thursday showed an impressive persistent slab release to approximately Size 3 in the Hurley area. The slab was triggered with a cornice cut on an apparently northeast aspect, though it should be noted that the cornice was not large. See the video here. The above report has combined with the Size 3 persistent slab avalanche observed up the Hurley on Friday to suggest an emerging pattern of persistent slab activity in that part of the region. The failure planes of each slide remain uncertain, but the early February surface hoar layer was suspected in Friday's occurrence.A MIN report from Thursday describes two skier-triggered Size 2 wind slab avalanches near Mt. Matier, serving as a reminder that our wind slab problem hasn't disappeared yet. While wind slabs remain a concern throughout the region, a low-probability/high consequence avalanche problem should be driving a more cautious approach to backcountry travel in the north of the region.

Snowpack Summary

Convective flurries have delivered a spotty 5-20 cm of new snow to the region over the past couple of days, with the greatest accumulations occurring in the south. Below the new snow, the previous snow surface consisted of surface facets and surface hoar to 6 mm, as well as sun crust on steep solar aspects. Beneath this new snow interface, 10-30 cm of recent snow overlies the widespread mid-February crust layer at higher elevations. Recent reports suggest this snow is well bonded to the crust. In the north of the region, a facet/surface hoar layer from early February down 60-100 cm remains reactive in snowpack tests and is suspected as the failure plane in at least one of two recent large persistent slab avalanches in the Hurley area. In the south of the region, the mid and lower snowpack are well settled and strong.

Problems

Persistent Slabs

An icon showing Persistent Slabs
A possible pattern of persistent slab avalanche activity has emerged in the northern part of the region. Backcountry users in this area are urged to dial back their terrain selection. Please see our snowpack discussion for more information.
Be aware of the potential for large avalanches due to the presence of deep weak layers.Be cautious in shallow snowpack areas where triggering is more likely.Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 4

Wind Slabs

An icon showing Wind Slabs
Watch for wind slabs lingering in the immediate lee of exposed terrain features in the alpine, especially on north-facing terrain. With up to 20 cm of new snow, areas in the south of the region will have a much higher risk of touchy new wind slabs.
Use ridges or ribs to avoid pockets of wind loaded snow.Be cautious as you transition into wind affected terrain.Be aware of increased wind slab danger in the south of the region.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Feb 25th, 2017 2:00PM

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