Avalanche Forecast

Issued: Mar 18th, 2017 4:24PM

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

Avalanche Canada shorton, Avalanche Canada

A cooling trend will eventually help stabilize the snowpack. Continually reassess conditions as you travel into avalanche terrain and be aware of the potential for deeper weaknesses in the snowpack.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

SUNDAY: Clearing skies following the storm, light to moderate west winds, alpine temperatures drop to around -10 C.MONDAY: Mix of sun and cloud, light winds, alpine temperature around -7 C.TUESDAY: Cloudy with sunny periods and isolated flurries, light winds, freezing level climbs to 1500 m with alpine temperatures around -3 C.

Avalanche Summary

On Friday, a large cornice fall missed a group of skiers on a north aspect in the Duffey area (see MIN report for details). The previous day another skier remotely triggered a size 1.5 avalanche on a nearby south aspect at treeline. On Saturday, explosive control produced a few size 2-2.5 storm slabs and a few natural storm slabs were reported in the northern part of the region.On Sunday, storm slabs may remain reactive in human triggers. In northern parts of the region, the deeper February weak layers continue to present a low probability / high consequence scenario.

Snowpack Summary

Storm snow amounts on Saturday totalled roughly 40 cm around Coquihalla and Allison Pass and 30 cm around Duffey Lakes. Freezing levels reached roughly 1400 m, resulting in rain and/or wet snow at lower elevations. Thicker wind slabs and large cornices likely exist in alpine terrain. The storm snow sits above a widespread rain crust up to about 2100 m, but the snow will likely form a good bond to this crust. In the north of the region, the February weak layers are 80-120 cm deep and include a buried surface hoar layer that recently produced a few persistent slab avalanches and a crust/facet layer that appears to be gaining strength. In the southern parts of the region, the lower snowpack is generally stable.

Problems

Storm Slabs

An icon showing Storm Slabs
Storm slabs may remain reactive at higher elevations and wind-affected terrain.
Be alert to conditions that change with elevation.Carefully evaluate terrain features by digging and testing on adjacent, safe slopes.Avoid freshly wind loaded features.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
Heavy triggers such as a cornice fall or a small avalanche could potentially step down to weak layers buried about 1 m deep in the northern parts of the region.
Pay attention to overhead hazards like cornices which could trigger persistent slabs.If triggered, storm slabs may step down to deeper layers resulting in very large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Mar 19th, 2017 2:00PM

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