Avalanche forecast

Sea To Sky

Nov 29 – 30, 2016Avalanche Canada
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Avalanche danger

Wed
Thu
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Forecast new snow is not expected to elevate the danger on Wednesday. If there is more than 10 cm in your area, consider the danger to be a bit higher.

Avalanche problems

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2
    Recent strong winds and heavy snowfall have been the perfect combo for large cornice development. To avoid a nasty ride, give fresh cornices a wide berth while traveling on ridgetops.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2
    Even though the storm has ended, storm slabs may remain touchy, especially on higher elevation, wind-exposed features. I'd give the snowpack time to settle and gain strength before pushing into big, exposed terrain.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Wednesday

Weather Forecast

Snow developing overnight with moderate southwest winds and freezing levels around 1000 metres. Expect 5-10 cm by Wednesday morning and another 5-10 cm during the day. Light westerly winds and a few cm of snow or flurries on Thursday. The next major storm is forecast on Friday, expect strong southwest winds and 20-35 cm of snow above 1500 metres.

Avalanche Summary

Some reports from Monday of skier controlled soft slab avalanches up to size 1.5 where the surface snow has slabbed up above a less dense (one finger over fist) layer of recent storm snow. However, explosives control on Sunday produced several soft storm slab avalanches on a variety of aspects and elevations. Most of the activity was in the size 1 range, although a few results to a size 2 were also noted. A few size 2 cornice collapses were also triggered with explosives in alpine terrain. Looking forward, relatively calm weather should allow for strengthening and settlement in the snowpack, and avalanche activity should taper-off. I'd still remain cautious of human-triggered storm slabs, especially in steeper, high elevation terrain.

Snowpack Summary

Snow depths increased rapidly last week bringing treeline snow depths to about 200 cm. Much of this recent storm snow has settled and gained significant strength. That said, the last burst of wind and snow on Saturday and Sunday created reactive soft storm slabs which appeared to be especially touchy in higher, wind-exposed terrain. Stormy weather also encouraged significant cornice growth, and new cornices are reported to be unseasonably large and fragile. Over a metre below the surface you'll find the thick mid-November crust. The reports we've received suggest a reasonable bond at this interface; however, I'd remain suspicious of this layer until the snowpack adjusts to the weight of all of the new snow. This may take a few more days. Below the crust, the snowpack is strong and well-settled.

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