Avalanche Forecast

Issued: Jan 29th, 2013 9:32AM

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

swerner, Avalanche Canada

Northwest Inland.

Summary

Confidence

Poor - Due to limited field observations

Weather Forecast

Wednesday: High pressure moves into the region gradually pushing out the low. Light snowfall amounts accompanied by NW ridgetop winds near 55km/hr. Alpine temperatures near -6.0 and freezing levels around 600 m. Thursday: Upper trough embedded in the flow causing unsettled conditions. Snow amounts 5-10 cm accompanied by moderate ridgetop winds from the West. Alpine temperatures near -5.0 and freezing levels rise to 700 m.Friday: Unsettled conditions continue. Snow amounts 5 cm with ridgetop winds light from the SW. Alpine temperatures -4.0 and freezing levels rising to 900 m.

Avalanche Summary

Loose dry sluffing from steep terrain. SSL forming, Skier triggered slab produced a size 2.0 on a SE aspect near 1400 m.

Snowpack Summary

New storm snow is building over a variety of old surfaces including old wind slabs, scoured thin slopes, blue ice, thin melt-freeze crusts and surface hoar. The new storm snow may have a poor bond with the old surfaces buried below.The average snowpack depth at treeline is near 100 cm but remains quite inconsistent across the region. A strong mid-pack currently overlies a weak base layer of facets/depth hoar. Triggering of this basal weakness may still be possible from thin spots, rocky outcrops or under the weight of larger triggers such as cornice fall and larger amounts of new storm snow.

Problems

Wind Slabs

New snow and strong shifting winds will build touchy wind slabs that are likely found behind terrain breaks such as ridges and ribs. Hollow sounds and cracking snow is a good indicator of unstable snow.

Avoid freshly wind loaded features.>Use ridges or ribs to avoid pockets of wind loaded snow.>Avoid lee and cross-loaded terrain near ridge crests.>Be cautious of sluffing in steep terrain; especially where terrain traps lurk below.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Deep Persistent Slabs

A deeply buried weak layer near the base of the snowpack could be triggered by large loads such as a cornice collapse or from a thin-spot trigger point.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Jan 30th, 2013 2:00PM