Avalanche Forecast

Issued: Nov 23rd, 2012 9:22AM

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

Avalanche Canada istorm, 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

The storm that arrived overnight Thursday moved out of the region Friday. Incoming air is looking cooler and drier. Precipitation: no significant snow or rain forecast through Monday. Wind: light SE Saturday veering to light NW Sunday and backing to the West on Monday. Temperature: cooling with below freezing temperatures at all elevations overnight and around 800m or 900 m during the day. Alpine temperatures around -5 to -10C. You're likely to see at least some sun this weekend, more likely on Sunday.

Avalanche Summary

Previous to Friday's storm, isolated size 2 avalanches were reported running on the early November crust. No reports from the region following Friday's storm. There was likely enough snow, when combined with strong winds, that natural avalanches released (wind slabs behind ridges?). My suspicion is that natural storm snow avalanches have now ended but the possibility of triggering a lingering pocket remains this weekend.

Snowpack Summary

No field reports since Friday's storm, however weather stations show enough new snow (15 cm) which came with enough wind (Moderate from the South) that wind slabs should be expected behind ridges and in cross-loaded terrain. Coquihalla and Cayoosh Passes have about 50cm of snow on the ground, while treeline areas have around a metre. Alpine areas likely have more snow, but also highly variable depths depending on wind exposure. 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.). 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, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Wind Slabs

An icon showing Wind Slabs
Fresh wind slabs below ridge crests, behind terrain features, and in cross-loaded gullies are expected to be sensitive to human triggers. Particularly where they are sitting on a previously exposed or lightly buried crust from early November.
Assess start zones carefully and use safe travel techniques.>Watch freshly wind loaded features.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Nov 24th, 2012 2:00PM