Avalanche Forecast

Issued: Mar 6th, 2017 3:17PM

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

Avalanche Canada triley, Avalanche Canada

Storm slabs continue to be a concern for human triggering. Avoid slopes where the buried sun crust and associated facets increase the likelihood of triggering.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

Overnight: Light to moderate northwest winds combined with convective flurries and alpine temperatures around -15. In some areas flurries may be heavy at times resulting in 5-10 cm. Tuesday: A mix of sun and cloud with periods of flurries and light southwest winds. Alpine temperatures remain around -15. Wednesday: Overcast with light winds and convective flurries, some areas may see 5-10 cm of new snow. Thursday: Overcast with convective flurries and light easterly winds. Alpine temperatures may be close to -20 in the morning.

Avalanche Summary

On Sunday we had one report of a natural cornice fall size 2.0 and a skier accidentally triggered a size 1.0 avalanche. Storm slab avalanches were widespread on Saturday up to size 2.5.

Snowpack Summary

Just under a week of stormy weather has blanketed the region in 45-70 cm of new snow. The snowfall was accompanied by moderate to strong southerly winds, which promoted the formation of touchy storm slabs at upper elevations. The new snow has buried faceted surface snow, thin sun crust on steep solar aspects, as well as surface hoar reported in sheltered areas in some parts of the region previous to the storm. About 75-100 cm below the surface you'll likely find the mid-February interface, which is composed of a thick rain crust up to about 1700 m, sun crusts on steep solar aspects, and spotty surface hoar on shaded aspects. Recent reports have suggested greater reactivity on this layer at lower elevations where the rain crust is more prominent. Professionals in the region have also warned that a 'threshold load' has been reached above this interface, particularly where it presents as a crust. Some lingering surface hoar layers from January are now down a metre or slightly more and the weak mid-December facets are down about 1.5 metres. These deep persistent weaknesses still have the potential to react to human triggers or smaller storm slab avalanches.

Problems

Storm Slabs

An icon showing Storm Slabs
As natural avalanche activity subsides, potential for human triggering storm slabs will persist. The touchiest conditions have been reported in wind affected areas and where the new snow overlies crust. (Steep south-facing slopes and below treeline)
Be alert to conditions that change with elevation.If triggered, the storm slabs may step down to deeper layers resulting in large avalanches.Use ridges or ribs to avoid pockets of wind loaded snow.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
A weak layer of facets is lingering near the base of the snowpack. The risk of triggering a deeper weak layer will be heightened while overlying storm slabs remain sensitive to human triggering. The greatest risk exists in shallow snowpack areas.
Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.Avoid lingering in runout zones.Avoid or use extreme caution around thin snowpack areas.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 4

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