Avalanche Forecast

Issued: Jan 20th, 2013 9:38AM

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.

Extent of solar radiation and warming influence is uncertain. Use extra caution as the day progresses especially on South facing slopes.

Summary

Confidence

Fair

Weather Forecast

Sunday night and Monday: The ridge of high pressure continues to bring dry conditions, well above normal temperatures (close to 0 degrees in the alpine), few clouds cover with valley cloudsÂ and light to moderate NW winds. Freezing level rising to 1400 m.Tuesday: The ridge is moving slowly Eastward bringing more mild temperatures, few clouds and valley clouds and lighter winds from the NW. Similar temperatures, with freezing level lowering to surface. Wednesday: A weak system should reach the region later during the day bringing light precipitation, cooler temperatures and Southerly winds.Â

Avalanche Summary

No new avalanche was reported.

Snowpack Summary

The warm temperatures and solar radiation forecasted for tomorrow could weaken the windslabs and persistent slabs, especially those found on steep South facing slopes.Â If surface snow becomes moist, loose wet avalanches could also take place, and even though small in size, they could become a problem if thrown off your feet in a terrain trap. As a general picture, around 40-60 cm of 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 hard to moderate 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

Solar radiation and warm temperatures could weaken some steep wind loaded slopes. Triggering a windslab could potentially step down to a deeper instability.

Cornices become weak with daytime heating, so travel early on exposed slopes.>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

Expected Size

1 - 5

Persistent Slabs

A cautious approach is recommended on steep south-facing slopes and sheltered terrain below treeline with daytime warming and solar radiation possibly weakening the snowpack.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Jan 21st, 2013 2:00PM