Avalanche Forecast

Issued: Mar 25th, 2014 9:11AM

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

triley, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

Overnight and Wednesday: Moderate Easterly winds overnight combined with flurries and cool temperatures. Strong outflow winds during the day with freezing levels close to valley bottoms.Thursday: Continued flurries and cool temperatures combined with moderate Easterly outflow winds.Friday: A chance of some sunny periods in the afternoon. Freezing levels below 500 metres.

Avalanche Summary

Some small size 1.0-1.5 wind slab avalanches were reported due to strong Easterly outflow winds transporting snow.

Snowpack Summary

Strong Easterly winds have been reported to have caused intense wind transport of the recent storm snow, developing pockets of wind slab on various aspects in the alpine and at treeline. Forecast cool temperatures are not expected to promote much settling or bonding of the near surface layers, and probably not much change to the persistent weak layers. The deeply buried persistent weak layers continue to provide moderate to hard sudden planar results in snow profile tests, but may be deep enough to require a heavy load for triggering. The March weak layer is a combination of hard wind-scoured slab surfaces in exposed terrain, facets and/or surface hoar in sheltered and north aspects, and sun crust on steep solar aspects. This layer is widespread throughout the forecast region and is now buried close to 150cm in most parts of the area. A late January/early February crust/facet/surface hoar combo is now buried 200 cm or more.

Problems

Storm Slabs

Forecast new snow may increase the load of recent storm slabs above a mix of old surfaces. Watch for pockets of wind transported snow at and above treeline.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>Use conservative route selection, stick to moderate angled terrain with low consequence.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 4

Persistent Slabs

The early March persistent weak layer is buried deep enough to produce large avalanches when triggered. The added load of the recent storm slabs may result in deep slab avalanches.

Assess start zones carefully and use safe travel techniques.>Avoid areas with overhead hazard.>Avoid runouts where triggering slopes from below is possible.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 5

Deep Persistent Slabs

The early February persistent weak layer is buried deeply in the snowpack and continues to be a concern. Heavy loads like cornice falls or storm slab avalanches in motion may trigger this weak layer resulting in very large avalanches.

Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.>Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Mar 26th, 2014 2:00PM