Avalanche Forecast

Issued: Feb 25th, 2017 4:16PM

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

Recent snowfall has resupplied wind slabs in the south of the region. Recent persistent slab activity should rein in terrain selection in the north.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Saturday night: Cloudy with scattered flurries bringing up to 5 cm of new snow. Winds moderate from the west. Sunday: A mix of sun and cloud. Winds light to moderate from the northeast. Freezing level to 400 metres with alpine temperatures of -10. Closer to 800 metres and -5 in the south of the region. Monday: A mix of sun and cloud. Winds light to moderate from the west. Freezing level to 200 metres with alpine temperatures of -11. Closer to 500 metres and -6 in the south. Tuesday: Mainly cloudy with isolated flurries bringing a trace to 5 cm of new snow, beginning in the evening. Winds light to moderate from the west. Freezing level to around 400 metres with alpine temperatures around -8.

Avalanche Summary

No new avalanches were reported on Friday. 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 the possibility of 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.Two MIN reports from Thursday describe three 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 the new snow interface, 10-30 cm of recent storm snow overlies the widespread mid-February crust layer at higher elevations. Reports suggest this snow is well bonded to the crust but has been undergoing faceting as a result of recent cold temperatures. 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.
Avoid steep convexities or areas with a thin or variable snowpack.Be cautious in shallow snowpack areas where triggering is more likely.Be aware of the potential for large avalanches due to the presence of deep weak layers.

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 recent snow, areas in the south of the region will have a higher risk of more reactive wind slabs.
Be aware of increased wind slab danger in the south of the region.Be cautious as you transition into wind affected terrain.Use ridges or ribs to avoid pockets of wind loaded snow.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

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

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