Avalanche Forecast

Issued: Feb 24th, 2019 4:12PM

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

Avalanche Canada shorton, Avalanche Canada

Conservative terrain choices are critical. Although the chance of triggering large avalanches is decreasing, the consequences of doing so are high.

Summary

Confidence

Moderate -

Weather Forecast

SUNDAY NIGHT: Clear, moderate northeast wind, alpine temperatures drop to -5 C.MONDAY: Sunny, light to moderate northeast wind, alpine high temperatures around -3 C.TUESDAY: Sunny, moderate northeast wind, alpine high temperatures around -6 C.WEDNESDAY: Sunny with cloudy periods, strong northeast wind, alpine high temperatures around -3 C.

Avalanche Summary

Several small (size 1) human triggered slabs were reported in the storm snow on Saturday and Friday. Loose dry sluffing was also observed in steep terrain.Persistent slab avalanches on the buried crust layer are still a serious concern. One occurred naturally on a south-facing feature at treeline elevation on Wendesday (see MIN report here). Last Monday, a fatal avalanche occurred on a steep feature at treeline elevation in the Mount Seymour backcountry (see here for incident report). Avalanche professionals involved in the rescue indicated wide propagation consistent with a persistent slab problem. The crown depth was variable - 40 to 100 cm, indicating there was also wind loading in that area.

Snowpack Summary

Roughly 30 cm of new snow sits above a mix of sun crusts and possibly some weak faceted snow and surface hoar. A widespread crust layer is buried 50-100 cm deep with weak snow above it that has produced large natural and human-triggered avalanche over the past week. These videos from Wednesday demonstrate how easy it is to trigger this weak layer (here and here). The reactivity of this layer appears to be worse in the south of the region (i.e. the North Shore Mountains) since this part of the region has seen more snow and it has consolidated into more of a slab. Unusually for this region, we expect this layer to remain reactive for some time into the future. The lower snowpack is settled and strong.

Problems

Persistent Slabs

An icon showing Persistent Slabs
A weak layer of facets over a crust is buried 50-100 cm deep. Triggering large avalanches on this layer remains possible in steep terrain.
Use conservative route selection, choose moderate angled and supported terrain with low consequence.Minimize exposure to sun exposed slopes when the solar radiation is strong.Be aware of the potential for wide propagations due to the presence of a buried weak layer.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Storm Slabs

An icon showing Storm Slabs
Storm slabs are possible to trigger in steep terrain as 30 cm of recent snow may be poorly bonded to the snow below.
If triggered the storm slabs may step down to deeper layers resulting in large avalanches.Choose well supported terrain without convexities.Use caution above cliffs where small avalanches may have severe consequences.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 1.5

Valid until: Feb 25th, 2019 2:00PM

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