Avalanche forecast

South Columbia

Feb 15 – 16, 2013Avalanche Canada
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Avalanche danger

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

Forecast new snow is expected to add a new load above the recent storm snow that may cause the buried February 12th weak layer to continue to be reactive.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–5
    Strong Northwest winds have created thick new windslabs that may be triggered by light additional loads. Wind slab fractures may propagate quickly due to the presence of buried surface hoar and/or sun crusts.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–6
    There are older layers of buried surface hoar and crusts that are unlikely to be triggered by the weight of a skier or sledder, but may be triggered by large additional loads like cornice fall or wind/storm slab avalanches in motion.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–5
    A new soft slab is developing above the recent buried crusts, wind slabs, and weak surface hoar crystals. This new slab may be very easy to trigger on steep rolls and unsupported terrain features.

Confidence

Fair - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

Overnight and Saturday: Moderate Westerly winds are expected as the ridge of high pressure flattens and a trough moves into the interior from the Northwest. Alpine temperatures should stay a few degrees warmer than seasonal overnight as the warm front delivers 5-10 cms. Moderate snow fall should start sometime in the early afternoon when the trailing cold front moves across the region. Expect 10-15 cms with cooler temperatures and gusty West winds.Sunday: Unsettled cool air will be left behind as the next ridge of high pressure builds over the interior. Expect light Northerly winds and alpine temperatures down to about -10.0.Monday: Mainly cloudy as the weak ridge of high pressure moves to the East.

Avalanche Summary

The storm slab continued to be reactive on Thursday. Skiers controlled avalanches up to size 1.5 and  accidentally released avalanches up to size 2.0. Explosives control in the highway corridor resulted in avalanches up to size 2.5 on North aspects at 2000 metres. There were also a couple of natural cornice falls up to size 2.0

Snowpack Summary

There is a lot of variability in the depth of the new snow slab and the new wind slabs. Areas that received 30-40 cms of new snow have developed thick new wind slabs at higher elevations that may be triggered by light additional loads. The storm slab in these areas has been reported to be reactive to skiers, as it slides easily on a layer of surface hoar that developed just previous to the latest storm. In some areas there is a sun crust that developed during the sunny weather last weekend that is a smooth and fast sliding layer for the new storm slab. Deeper weak layers continue to show planar results in snow profile tests down about 70 cms and also at about 100 cms. These deeper layers are less likely to be triggered by skiers, but cornice falls or other large triggers may step down and result in large avalanches.

Regions covered