Avalanche Forecast

Issued: Jan 19th, 2013 9:40AM

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.

slemieux, Avalanche Canada

Purcells.

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Saturday night and Sunday:Â Ridge of high pressure continues to dominate for the whole period. No precipitation, mild temperatures, broken clouds and valley clouds and moderate Westerly winds becoming light on Sunday.Monday: Similar conditions with warmer temperatures and freezing level rising to 1400 m. Tuesday: Dry conditions persist, light SW winds and freezing level around 1300 m.

Avalanche Summary

A slab avalanche size 2 was reported from the Jumbo area. It would have been triggered by a cornice fall on a steep alpine slope.

Snowpack Summary

Recent 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. They appear to be more reactive in the middle part of the region rather than in the Northern part of the region. 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 were formed behind terrain breaks such as ridges and ribs. It may be possible for a wind slab to step down to a deeper instability.

Choose well supported terrain without convexities.>Be aware of the potential for wide propagations due to the presence of hard windslabs.>

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

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: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 5

Valid until: Jan 20th, 2013 2:00PM