Avalanche Forecast

Issued: Mar 9th, 2017 4:24PM

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 cam_c, Avalanche Canada

Storm slabs are primed for people triggering large avalanches, and have the potential to step down to deeper persistent weaknesses resulting in very large and dangerous avalanches.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

FRIDAY: Cloudy with 5-10cm of fresh snow accompanied by light to moderate southerly winds. Alpine temperatures reaching -10 C.SATURDAY: Cloudy with 3-5cm of fresh snow accompanied by light to moderate southerly winds. Alpine temperatures reaching -5 C.SUNDAY: Cloudy with another 3-5cm of fresh snow accompanied by light to moderate SW winds. Freezing levels rising as high as 1500m.

Avalanche Summary

Reports from Wednesday include observations recent 40-70cm deep natural storms slab avalanches up to Size 2.5, and a 40cm deep skier triggered Size 1.5 persistent slab avalanche.

Snowpack Summary

40-80cm of settled storm snow from the past week is bonding poorly to faceted snow, thin sun crust on steep southerly aspects, as well as surface hoar in sheltered areas in some parts of the region. Touchy storm slabs can be found at all elevations with weaknesses within and under this recent snow. Previous southerly and more recent northerly winds have loaded lee aspects with particularly deep and touchy wind slabs. About 60-120 cm below the surface you'll likely find the mid-February persistent weakness, 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
Weaknesses within the recent storm snow are susceptible to human triggering. These storm slabs are particularly deep and touchy on slopes loaded by southerly winds and have the potential to step down to deeper persistent weaknesses.
Use ridges or ribs to avoid pockets of wind loaded snow.If triggered, the storm slabs may step down to deeper layers resulting in large avalanches.Be alert to conditions that change with elevation.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
Persistent weakness layered throughout the snowpack create the potential for very large step-down avalanches. The risk of triggering a deeper weak layer will be heightened while overlying storm slabs remain sensitive to human triggering.
Avoid or use extreme caution around thin snowpack areas.Avoid lingering in runout zones.Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3

Valid until: Mar 10th, 2017 2:00PM