Avalanche Forecast

Issued: Jan 19th, 2013 9:51AM

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

Cariboos.

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Saturday night and Sunday: Ridge of high pressure continues to dominate for the whole period. No precipitation, mild temperatures, scattered clouds and valley clouds and moderate Westerly winds becoming light on Sunday.Monday: Similar conditions with warmer temperatures and freezing level rising to 1100 m. Tuesday: Dry conditions persist, light S winds and freezing level around 1000 m.

Avalanche Summary

Several recent natural slab avalanches up to size 1.5 were reported which would have released in the new storm snow. A glide crack released to the ground producing a size 2.5 was also reported on a SW aspect.

Snowpack Summary

15-20 cm of new snow fell with strong NW switching to SW winds creating windslabs on lee side in alpine and at treeline. The new windslabs were producing some sudden planar tests results and were reactive to skier traffic. The forecasted mild temperatures and reduced wind transport should give them a chance to improve the bond with the underlying surface. Cornice growth has also been observed. The storm snow sits above surface hoar (found especially below treeline in sheltered areas down around 40 cm), 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. Indeed, snow tests showed sudden planar results in the easy to moderate range. A strong mid-pack overlies a weak facet/crust layer near the base of the snowpack, which is now considered inactive.

Problems

Wind Slabs

Recent wind event and new snow has formed new wind slabs on lee slopes in the alpine and at treeline.

Avoid windloaded convex and unsupported slopes.>Avoid lee and cross-loaded terrain near ridge crests.>

Aspects: North, North East, East, South East, South, South 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. Carefully assess steep south-facing slopes and slopes below about 1900 m, where persistent weaknesses are most likely to be lurking.

Dig down to find and test weak layers before committing to a line.>Avoid steep open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 5

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