Avalanche Forecast

Issued: Mar 17th, 2017 5:26PM

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

cgarritty, Avalanche Canada

Northwest Inland.

Sustained and shifting winds are driving a wind slab problem at higher elevations. The potential for a wind slab release to trigger a deeper persistent slab can't be overlooked.

Summary

Confidence

High -

Weather Forecast

Saturday: A mix of sun and cloud with isolated flurries and a trace of new snow. Light southwest winds. Alpine temperatures of -9. Sunday: A mix of sun and cloud with isolated flurries and a trace of new snow. Moderate to strong southwest winds. Alpine temperatures of -8. Monday: Cloudy with sunny periods. Light southeast winds. Freezing level rising to 1000 metres with alpine temperatures of -7.

Avalanche Summary

No new avalanches have been reported, but a report from the north of the region detailed a remotely triggered Size 2 storm slab releasing on a northeast aspect at 1400 metres on Wednesday. The slab depth was 50 cm. Numerous natural avalanches up to size 2.5 were reported from the west of the region in the Howsons on Tuesday. Natural avalanches up to size 2.0 were reported from the Hankin area on Monday.

Snowpack Summary

At treeline and above, ongoing winds have been redistributing recent storm snow and light new snow amounts into wind slabs in lee terrain. New snow amounts taper with elevation and lie over a supportive crust at about 1300 metres and below. At higher elevations, the recent snow is incrementally loading a weak interface that was buried in late February. The interface is composed of facets, crusts, and surface hoar and may be 40-60 cm deep. There's uncertainty about the distribution and reactivity of this interface, but it recently proved reactive under skier traffic in the north of the region. The mid-pack is well consolidated, but sits above weak, sugary snow near the ground. This deeper basal weakness remains an ongoing concern in thin rocky start zones and in shallow snowpack locations.

Problems

Wind Slabs

Moderate to strong winds have shifted from southeast to southwest, leaving fresh wind slabs on a wide range of aspects. Use increasing caution as you enter wind affected terrain, especially in the lee of exposed terrain features at treeline and above

Be increasingly cautious as you transition into wind affected terrain.Be alert to conditions that change with elevation.If triggered, wind slabs may step down to deeper layers and result in large avalanches.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Deep Persistent Slabs

A lingering weakness at the bottom of the snowpack is here to stay. It will be most reactive in thin rocky start zones and in shallow snowpack locations.

Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Mar 18th, 2017 2:00PM