Avalanche Forecast

Issued: Mar 24th, 2014 9:34AM

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

triley, Avalanche Canada

Northwest Coastal.

Forecast new snow and wind are expected to increase the avalanche danger.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Tuesday

Weather Forecast

Overnight and Tuesday: Some Pacific moisture (3-5 cm) is expected to push into the Northern coastal areas and then slide inland. Mostly overcast with light precipitation, cold alpine temperatures, and moderate to strong Southwest winds. Freezing levels at about 500 metres.Wednesday: Overcast with light precipitation and light winds. Freezing level about 500 metres and alpine temperatures around -15.Thursday: Overcast with a chance of sunny breaks in the afternoon. Light Easterly winds and temperatures around -15 in the alpine.

Avalanche Summary

We have a report of size 3.5 natural avalanche from a Northwest aspect that released down 100-150 cm on the deeply buried February persistent weak layer. It is suspected that this avalanche was triggered sympathetically to a size 1.5 solar release on an adjacent slope.

Snowpack Summary

The area has received 75 to 150cm of snow over the past 5 to 7 days. The recent storm snow arrived with strong winds and produced wind slabs at tree line and above and increasing the depth on the slab that now overlies the March persistent weak layer. In addition, much of the recent storm snow has fallen on a melt freeze and/or rain crusts that exist in most parts of the region below 1200 metres. 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 still showing up in snowpack tests with moderate to hard shear tests. It appears to be dormant for the time being, but a sudden increase in load, a cornice failure, or a large rainfall event could "wake up" this layer and result in a large destructive avalanche.

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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

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.

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

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.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out 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

Expected Size

3 - 6

Valid until: Mar 25th, 2014 2:00PM