Avalanche Forecast

Issued: Jan 18th, 2013 9:03AM

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

pgoddard, Avalanche Canada

Purcells.

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Saturday: Moderate to strong NW winds. Alpine temperature near -3. No snow.Sunday: Light to moderate W winds. Alpine temperature near -3. No snow.Monday: Light to moderate W winds. Alpine temperature near -2. No snow.

Avalanche Summary

A couple of slabs (size 1 and 2.5) failed naturally on NW aspects at around 2400 m on Thursday.

Snowpack Summary

Ongoing strong to extreme NW to SW winds have stripped windward aspects and left wind slabs on many lee slopes, even below treeline. Around 40-60 cm settled storm snow sits above surface hoar (found especially at and below treeline in sheltered areas), a sun crust (on steep S to SW -facing slopes) and facets. The distribution of these weaknesses is patchy, but where they exist, it may still be possible to trigger a large avalanche with the weight of a person or snowmobile. Test results on these interfaces vary from no result to moderate, sudden results. A strong mid-pack overlies a weak facet/crust layer near the base of the snowpack, which is now considered inactive.

Problems

Wind Slabs

Wind slabs may be found behind terrain breaks such as ridges and ribs. It may be possible for a wind slab to step down to a deeper instability.

Be aware of the potential for wide propagations due to the presence of hard windslabs.>Travel on ridgetops to avoid wind slabs on slopes below.>Do not travel on slopes that are exposed to cornices overhead.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Persistent Slabs

Triggering persistent slabs is becoming less likely, but a cautious approach is still advised. Take extra care on steep south-facing alpine slopes and in sheltered terrain below treeline.

Dig down to find and test weak layers before committing to a line.>Be aware of thin areas that may propagate to deeper instabilites.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

1 - 6

Valid until: Jan 19th, 2013 2:00PM