Avalanche Forecast

Issued: Mar 16th, 2017 4:30PM

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

cgarritty, Avalanche Canada

Northwest Coastal.

Wind slabs have emerged as the primary avalanche problem in the region, but they aren't the only one. Deeper in the snowpack, our persistent slab problem lingers on.

Summary

Confidence

Moderate -

Weather Forecast

Thursday night: Flurries bringing 10-15 cm of new snow. Moderate to strong southeast winds.Friday: Flurries bringing approximately 10 cm of new snow. Moderate to strong south winds. Freezing level to 600 metres with alpine temperatures around -7.Saturday: Mainly cloudy with scattered flurries and a trace of new snow. Light to moderate southwest winds. Freezing level to 400 metres with alpine temperatures around -7.Sunday: Cloudy with scattered flurries and a trace of new snow. Moderate southwest winds. Freezing level to 500 metres with alpine temperatures around -6.

Avalanche Summary

Wednesday's reports include further observations of the widespread natural avalanche cycle that occurred on Tuesday. Natural wet slab avalanches ran up to size 2.5 and loose wet avalanches ran up to size 1.5. Below treeline elevations were especially active in the north of the region. Reports have been limited due to poor visibility and travel conditions.

Snowpack Summary

Recent stormy weather has blanketed the region with storm slabs that are approximately 30-60 cm deep, with much deeper areas where the wind has transported the recent snow. As these slabs have formed a bond to the surface, ongoing winds and light new snow accumulations have seen our primary hazard transition to wind slabs. At treeline and above, new snow and wind have been loading and stressing a weak interface from February composed of facets, crust, and surface hoar buried over a metre deep. This layer was active prior to the storm and remains an ongoing concern. After below zero temperatures on Wednesday night, a surface crust has likely formed over moist or wet snow previously reported at 1100 metres and below.

Problems

Wind Slabs

Forecast flurries will combine with strong south to southeast winds and form fresh wind slabs on Friday. Use increasing caution as you enter wind affected terrain expect touchy new slabs in the lee of exposed terrain features at treeline and above.

Minimize overhead exposure during periods of heavy loading from new snow, wind.Use ridges or ribs to avoid pockets of wind loaded snow.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Persistent Slabs

A persistent weak layer from late February is buried up to a metre deep and continues to show reactivity in snowpack tests. Potential still exists for a rider to directly trigger this layer or for a smaller wind slab avalanche to act as a trigger.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 4

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