Avalanche forecast

Sea To Sky

Dec 3, 2016Avalanche Canada
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Avalanche danger

Sat
Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

The current storm is ramping up avalanche danger where new snow is accumulating. Choose conservative terrain and watch for wind loaded features.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–3
    The mid-November crust is now buried up to 200 cm deep. Storm loading may allow this layer to react where the snowpack is thin or variable. A large avalanche within the storm slab may also provide enough of a trigger to step down to this layer.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–3
    Storm slabs are growing larger and more reactive with new snow. Strong southwest winds have loaded lee slopes and terrain features.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

SATURDAY:  New snow amounts 5-10 cm accompanied by moderate westerly winds. Freezing levels to 1100 metres with alpine temperature to -6SUNDAY: Isolated flurries with moderate northwest winds shifting to northeast. Freezing levels dropping to valley bottom with alpine temperatures to -9.MONDAY: No new snow, light winds from the northeast, freezing levels dropping to valley bottom with alpine temperatures to -12.

Avalanche Summary

Fresh storm slabs are increasing the load on a weak layer that was until now too shallow to present a significant hazard. Expect both the reactivity and the destructive potential of this layer to increase as new snow accumulates and settles. Increased loading also raises concern for a deep persistent layer that is now buried up to 200cm deep in the snowpack. Both natural and rider triggerable loose dry avalanches out of steep terrain can also be expected as new snow accumulates.

Snowpack Summary

A fresh storm slab is blanketing the region, continuing to bury a surface hoar layer that could be found up to 15cm deep in the snowpack on Thursday. Areas with this layer and where previously wind affected surfaces exist will be more reactive as the new load increases. Watch for shallow wind affected areas that will not gain strength as quickly as deeper, well settled snowpack areas. Snow depths increased rapidly last week, bringing treeline snow depths to about 200 cm. The mid-November crust is buried anywhere from 20-200 cm depending on aspect and elevation. While this crust has been unreactive thus far, increasing load may bring it to its breaking point, especially in areas with shallow or variable snowpack depth.

Regions covered