Avalanche Forecast

Issued: Mar 27th, 2014 9:03AM

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

triley, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Fair - Wind effect is extremely variable

Weather Forecast

Overnight and Friday: Overcast and cool overnight with freezing levels dropping down to valley bottoms. Continued strong Easterly outflow winds during the day with freezing levels rising to 500 metres.Saturday: Cool and overcast with a chance of flurries and freezing levels rising to 700 metres. Outflow winds are expected to continue from the East.Sunday: Chance of broken skies and periods of sun with a weak Northwest flow. Freezing levels rising to about 600 metres.

Avalanche Summary

No new avalanches reported.

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

Wind Slabs

Strong Easterly outflow winds have developed hard wind slabs in the alpine and at treeline.

Watch for areas of hard wind slab in steep alpine features.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 4

Persistent Slabs

The early March persistent weak layer is buried deep enough to produce large avalanches when triggered. Periods of solar radiation may increase the sensitivity to triggering this buried weak layer.

Avoid areas with overhead hazard.>Avoid runouts where triggering slopes from below is possible.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 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 convexities or areas with a thin or variable snowpack.>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

Unlikely - Possible

Expected Size

3 - 6

Valid until: Mar 28th, 2014 2:00PM