Avalanche Forecast

Issued: Nov 18th, 2011 9:04AM

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

Avalanche Canada triley, Avalanche Canada

This bulletin is based on limited data. Local variation in conditions and danger levels are likely to exist. To produce more accurate forecasts, we need information. Please send an email to forecaster@avalanche.ca

Summary

Confidence

Poor - Due to limited field observations

Weather Forecast

The ridge of high pressure has moved over the interior mountains and has brought cooler temperatures and drier conditions. Saturday is forecast to be mostly sunny and cold (-20.0 c) above treeline. Sunday should continue to be cold and mostly clear. The next storm is forecast to move in from the coast late Monday or overnight into Tuesday.

Avalanche Summary

A cycle of natural avalanche activity was observed in Quartz Creek on Sunday. Wind slabs (20cm deep) and persistent slabs (60cm deep) were observed. Persistent slabs were propagating widely and running on a weakness towards the base of the snowpack. Observations are limited to the northern Purcells so I don't know if this kind of thing is still occurring here.

Snowpack Summary

There is significant variability in the snowpack across the region. Snowpack depth at treeline varies from around 40-130cm. Up to 50cm of snow fell late last week and over the weekend, which was redistributed by strong winds blowing first from the south and then from the north-west. A basal layer of facets was reported in the Dogtooth Range, with a weak interface between the lower facets and recent storm snow. Observations are limited. New snow and wind are in the forecast although not as much as in the Columbias to the west. Some new windslab formation is possible.

Problems

Wind Slabs

An icon showing Wind Slabs
Strong southerly, then north-westerly, winds have shifted snow onto downwind slopes.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
Over the weekend, widespread storm slab activity was observed. Weak snow at the base of the snowpack will take time to gain strength. Steep or exposed terrain should be treated with suspicion. No new info so will keep this problem in for now.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Nov 19th, 2011 8:00AM

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