Avalanche Forecast

Issued: Nov 24th, 2012 8:25AM

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 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

Fair - Due to limited field observations

Weather Forecast

Synopsis: The weather pattern is changing as a ridge of high pressure builds in from the southwest resulting in drier conditions and slightly cooler temperatures for the next few days. Sunday: A mix of sun and cloud. The freezing level is around 800-1000m. Winds are generally light. Monday: A mix of sun and cloud. The freezing level is around 1000m. Tuesday: Most likely another dry day, but we should see a frontal system arrive Tuesday night or Wednesday morning.

Avalanche Summary

Avalanche control on Whistler Mountain on Saturday produced one Size 2 avalanche on a northeast aspect that appeared to release on the early November facet/crust weakness. The arrival of cooler and drier weather will reduce the likelihood of natural avalanches, but human triggered avalanches are still possible.

Snowpack Summary

New wind slabs have likely formed in exposed northwest to northeast aspects at treeline and in the alpine. The main snowpack feature worth noting is a rain crust buried in early November and now down around 80cm at treeline as as deep as 1.5m in alpine areas. A weak layer of facets on top of and within this crust is worth remaining suspicious about (sudden collapse fracture character with propagation potential with snowprofile/ snowpack tests). Widespread whumpfing and cracking on this layer has also been reported from the Whistler area. Because this weakness is so close to the ground in most areas, associated avalanche activity will likely be limited to slopes with smooth ground cover (e.g. scree slopes, rock slabs, summer firn, glaciers, etc.). The total snowpack depth at treeline is around a metre. Alpine areas are deeper but more variable. Most slopes below treeline are still below threshold depths for avalanches. 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 might be a concern with this weakness.
Be aware of the potential for full depth avalanches due to deeply buried weak layers.>Whumpfing is direct evidence of a buried instability.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Wind Slabs

An icon showing Wind Slabs
Fresh wind slabs below ridgecrests, behind terrain features, and in cross-loaded gullies may remain sensitive to human triggers, particularly where they are sitting on a previously exposed or lightly buried crust from early November.
Use ridges or ribs to avoid pockets of wind loaded snow.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Nov 25th, 2012 2:00PM