Avalanche Forecast

Issued: Nov 26th, 2012 8:48AM

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

Avalanche Canada Peter, Avalanche Canada

This bulletin is based on limited data. Local variations in conditions are likely to exist. Check out the forecaster's blog for further details on interpreting early season bulletins.

Summary

Confidence

Poor - Due to limited field observations

Weather Forecast

Synopsis: A ridge of high pressure should maintain sunny skies for Tuesday before giving way to a frontal system on Wednesday. Tuesday: A mix of sun and cloud. Freezing level at around 1400 m (an above freezing layer between 1800-2200 m is possible). Winds light from the south. Wednesday: Increasing cloud with precipitation developing. Expect 5-10 cm overnight. Freezing level around 1800m, lowering to 1400 m overnight. Thursday: Moderate precipitation – 10-20 cm. Freezing level around 1400 m. Winds should be moderate to strong from the south-southeast.

Avalanche Summary

There are no new reports from the region. Cooler and drier conditions should decrease the likelihood of natural activity, but human triggered avalanche remain possible, particularly on exposed wind loaded slopes and cross-loaded gullies. Also, be cautious in terrain with smooth ground cover and a thin or variable snowpack where is might be possible to trigger the early November persistent weakness.

Snowpack Summary

Recent storm snow has probably settled and strengthened under cooler temperatures. Dense wind slabs may still be susceptible to triggering in steep lee terrain. The main snowpack feature is a rain crust buried early November and now down around 80cm at treeline. A weak layer of facets sitting on top of this crust shows "collapse" fracture character and the ability to propagate. Widespread whumpfing and cracking on this layer has also been reported. It's mostly a concern at upper treeline and alpine elevations on slopes with smooth ground cover (e.g. scree slopes, rock slabs, summer firn, grass, etc.). Coquihalla Pass and Cayoosh Pass have around 50cm on the ground at the road elevation. Treeline areas have around 100-120 cm Alpine areas likely have more snow, but also highly variable depths depending on wind exposure. For more information check out the telemarktips.com forum, the Mountain Conditions Report, and Wayne Flann's Avalanche Blog.

Problems

Persistent Slabs

An icon showing Persistent Slabs
Large avalanches running on a crust near the base of the snowpack are possible, particularly on slopes with smooth ground cover. Remote triggering and step-down avalanches are a concern with this weakness.
Whumpfing is direct evidence of a buried instability.>Carefully evaluate and use caution around thin snowpack areas.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Nov 27th, 2012 2:00PM