Avalanche forecast

Sea To Sky

Nov 23 – 24, 2012Avalanche Canada
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Avalanche danger

Sun
Mon
Alpine
No rating
Treeline
No rating
Below
No rating
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Highlights

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.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–4
    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.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–3
    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.

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

In the limited reports we have, Friday's storm snow is quite reactive with natural avalanches to size 1.5 reported near treeline in the Whistler area. I suspect the arrival of forecast cooler temperatures will end natural activity; however, I suspect human triggering may still be worth thinking about at higher elevations. Explosive testing in the Whistler area only released few and small avalanches on the the early Nov. crust.

Snowpack Summary

The total snowpack depth at treeline is around a metre. Alpine areas are deeper but more variable with fat drifts and boney rocks. Most slopes below treeline are still below threshold depths for avalanches. Weaknesses likely exist within the recent storm snow, but should heal quickly. 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; however, explosive testing near Whistler didn't generate many results). 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.). For more information check out the telemarktips.com forum , the Mountain Conditions Report, and Wayne Flann's Avalanche Blog.

Regions covered