Avalanche Forecast

Issued: Mar 6th, 2017 4:33PM

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

Avalanche Canada triley, Avalanche Canada

Storm slabs continue to be a concern for human triggering. Storm slabs in motion may step down to buried persistent weak layers resulting in large and dangerous avalanches.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

Overnight: Flurries or light snow resulting in 3-5 cm of new snow combined with moderate southwest winds. Tuesday: Mostly sunny with moderate westerly winds and alpine temperatures around -15. Wednesday: overcast with light snow resulting in 3-5 cm of new snow combined with light southwest winds. Thursday: A mix of sun and cloud with increasing cloud and wind late in the day as the next system moves into the region.

Avalanche Summary

On Sunday, natural storm slab avalanches were reported up to size 3.0, and explosives control resulted in storm slab avalanches up to size 3.0.

Snowpack Summary

Just under a week of stormy weather has delivered a wide ranging 25-70 cm of new snow to the region, with the bulk of the new snow arriving over Friday night and blanketing localized pockets with up to 40 cm. The new snow has buried widely reported faceted surface snow as well as surface hoar reported at about 3mm on shaded aspects before the storm. Moderate to strong southerly winds accompanied the new snow, promoting the formation of touchy storm slabs at all elevations. Multiple reactive shears have recently been reported within this recent storm snow. Now roughly 40-90 cm below the surface you'll likely find the mid-February interface which is composed of a thick rain crust up to about 2000 m, sun crusts on steep solar aspects, and spotty surface hoar on shaded aspects. This layer has produced easy results in recent snowpack tests and has proven especially reactive on steep solar aspects. Several deeper weak layers also remain a concern, including the February 3rd surface hoar layer (50-130 cm deep), and the mid-January surface hoar layer in the northern Purcells (about 130 cm deep). Basal facets may still be reactive in shallow, rocky start zones.

Problems

Storm Slabs

An icon showing Storm Slabs
Up to 40 cm of new snow fell over Friday night under the influence of strong southerly winds. Touchy storm slabs now blanket much of the region and the strong potential still exists for human triggering the full depth of our recent storm snow.
Be increasingly cautious as you transition into wind affected terrain.Be alert to conditions that change with elevation.If triggered, storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3

Persistent Slabs

An icon showing Persistent Slabs
Several persistent weak layers buried 75-140 cm deep remain a concern, especially while touchier storm slabs carry the risk of 'stepping down' to one of these deeper weak layers. The greatest risk exists in shallow snowpack areas.
Be aware of the potential for large avalanches due to the presence of deeply buried weak layers.Avoid steep convexities or areas with a thin or variable snowpack.Be aware of overhead hazards and avoid lingering in runout zones.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Mar 7th, 2017 2:00PM