Avalanche Forecast

Issued: Mar 10th, 2017 4:37PM

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

Snow and wind will keep storm slabs touchy, and coupled with the potential for cornice triggers, the likelihood large persistent slabs is expected to increase.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

SATURDAY: Cloudy with 3-5cm of fresh snow accompanied by light to moderate southerly winds. Alpine temperatures reaching -5 C.SUNDAY: Cloudy with another 5-10cm of fresh snow by morning and continued light flurries throughout the day accompanied by moderate SW winds. Alpine temperatures hovering around -5 C.MONDAY: Cloudy with another 5cm by morning and light snowfall throughout the day accompanied by moderate to strong SW winds and freezing levels rising as high as 2000m.

Avalanche Summary

Reports from Thursday include a cornice collapse that triggered a Size 3 slab avalanche directly below in steep, rocky unsupported terrain. 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

5-15cm of fresh snow adds to the 40-80cm of settled storm snow from the past week that 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. 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 weaknesses from January are now down over a metre 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.
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

Likely

Expected Size

1 - 3

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.
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: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 4

Valid until: Mar 11th, 2017 2:00PM