Avalanche Forecast

Issued: Mar 16th, 2017 5:12PM

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

Avalanche Canada shorton, Avalanche Canada

Fresh snow will be touchy in wind affected terrain on Friday, while another wet storm is lined up to elevate the danger this weekend.

Summary

Confidence

Moderate - Track of incoming weather systems is uncertain on Saturday

Weather Forecast

FRIDAY: Isolated flurries before the next storm arrives Friday evening, strong southwest winds, alpine temperatures around -7 C.SATURDAY: Storm starts Friday night and delivers 15-25 cm, strong southwest winds, freezing level up to 1500 m with alpine temperatures around -4 C.SUNDAY: Clearing skies following the storm as alpine temperatures drop to around -10 C, moderate west winds.

Avalanche Summary

On Wednesday, evidence of a recent widespread natural avalanche cycle was reported in the northern part of the region. The avalanches included several size 2-3 storm slabs, a number of which stepped down to weak layers over a metre deep. Large cornice failures were also reported. One small skier triggered avalanche was reported on a north-facing wind loaded feature at 1950 m. There are no recent reports from the southern part of the region.On Friday, the most recent snow is expected to form new wind slabs in exposed terrain that may bond poorly to a buried rain crust. It has become difficult to trigger the February weak layers but there is still a chance that a smaller wind slab avalanche or a cornice fall could still step down and release a persistent slab avalanche.

Snowpack Summary

By Friday morning expect 10-20 cm of recent snow sitting above a widespread layer of wet snow up to about 2100 m. The wet snow layer is likely turning into a crust and may become a weak layer as storm snow accumulates. Strong south winds are likely forming wind slabs in the lee of exposed terrain, which may bond poorly to the crust. In the north of the region, the February weak layers are now down 80-120 cm. The layer of buried surface hoar has recently produced a few persistent slab avalanches. The crust/facet layer appears to be gaining strength but may also still be reactive in isolated areas. In the Coquihalla area, the crust/facet layer is down well over 1 m and appears to have gone dormant.

Problems

Wind Slabs

An icon showing Wind Slabs
The new snow with strong alpine winds has likely formed fresh wind slabs at higher elevations. These slabs will sit over a crust in many areas and are expected to be touchy. Cornices are also reported to be large and may still be weak.
Give cornices a wide berth when travelling on or below ridges.Avoid freshly wind loaded features.Be alert to conditions that change with elevation.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
A weak layer down around 1 metre is creating a low probability/high consequence scenario. It is unlikely to directly trigger this layer but a small avalanche or cornice fall could still step down to it.
Pay attention to overhead hazards like cornices which could trigger persistent slabs.Be aware of the potential for large avalanches due to the presence of deeply buried weak layers.If triggered, wind slabs may step down to deeper layers resulting in very large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Mar 17th, 2017 2:00PM

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