Avalanche Forecast

Issued: Jan 30th, 2013 10:00AM

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

swerner, Avalanche Canada

Northwest Inland.

Summary

Confidence

Poor - Due to limited field observations

Weather Forecast

Thursday:Â Cloudy, unsettled conditions. Snow amounts up to 10 cm. Ridgetop winds blowing 30-50 km/hr from the West. Alpine temperatures near -2 and freezing levels rising to 800 m.Friday: Continued cloudy skies and snow amounts near 5 cm. Ridgetop winds light from the SW. Alpine temperatures near -2 with freezing levels rising to 900 m.Saturday: Snow amounts 5-10 cm with ridgetop winds light from the South. Alpine temperatures near -3 and freezing levels sitting near 800 m.

Avalanche Summary

Loose dry sluffing from steep terrain. One skier triggered size 2.0 from a NE aspect around 1280 m, from a 40 degree slope.

Snowpack Summary

New storm snow (30-50 cm) 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. With little observations from the field its hard to get a good handle on possible persistent weak layers. I stress the importance to dig down and become familiar with the snowpack in your neck of the woods. Look for, and test potential weak layers. Observe their reactivity before dropping into your run or line.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.>Avoid lee and cross-loaded terrain near ridge crests.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 5

Persistent Slabs

Buried beneath the new snow sits a surface hoar/crust/facet weakness. This may be sensitive to rider triggers in steeper sheltered terrain or over convex rolls.

Dig down to find and test weak layers before dropping into your run or line.>Whumpfing is direct evidence of a buried instability.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 5

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.

Be aware of thin areas that may propagate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Jan 31st, 2013 2:00PM