Avalanche forecast

North Columbia

Feb 24, 2018Avalanche Canada
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Avalanche danger

Sun
Mon
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

New snow (possibly 20 cm by Sunday) and wind will continue to build slabs and cornices at upper elevations. Sloughing, and cracking around skis and sleds are signs that the new snow is bonding poorly to the old surface.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–2.5
    New snow and wind are adding to reactive wind slabs that exist in many areas the alpine as well as open areas at, or near treeline. Previous strong winds have also formed large, fragile cornices at ridge tops.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–4
    Buried weak layers exist in the snowpack and may be reactive to large triggers such as a cornice or step-down from a wind slab release. Human triggering may also be possible from shallow or thin. rocky, unsupported terrain.

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

TONIGHT: Flurries. Accumulation up to 5 cm. Ridge wind light, southwest. Temperature -16. Freezing level valley bottom.SATURDAY: Cloudy, light flurries increasing overnight. Accumulation 5 cm. Ridge wind light, southwest. Temperature -10. Freezing level valley bottom.SUNDAY: Snow. Accumulation 10-15 cm. Ridge wind moderate to strong, west. Temperature -8. Freezing level 500 m. MONDAY: Cloudy, light flurries. Accumulation trace. Ridge wind light, west. Temperature -8. Freezing level 700 m.

Avalanche Summary

Tuesday through Thursday there have been numerous reports of skier triggered slab avalanches up to size 2 on predominantly steep, southeast to southwest-facing features between 1900-2000 m, that failed on the mid-February crust. As well as explosive control results up to size 2 and a remotely triggered (from a distance) pocket of hard wind slab near ridge top. On Monday, natural wind slab avalanches to size 2.5 were reported on a southwest through northwest aspects between 1800m and 2400m.Last weekend (Feb 17 & 18) we there were reports of widespread natural wind slab activity above 1900m on primarily south east through west aspects, as well as a wind slab release stepping down to deeper weak layers and triggering a size 3.5 persistent slab, on a south west aspect near 2300m. Although deeper, persistent avalanche activity has become less frequent over the past week, light triggers in shallow rocky areas, as well as large triggers such as a cornice collapse or step down from a wind slab release, still have the potential to result in large destructive avalanches.

Snowpack Summary

A light dusting of new snow on Friday now covers 40-60 cm of storm snow from last week that has settled into a slab and been redistributed with previously strong winds into stiff wind slabs in wind-exposed areas. These accumulations sit on an interface the was buried mid-February consisting of; a mix of older wind slabs in exposed higher elevation terrain, a sun crust on steep solar aspects, a rain crust below 1600m, and surface hoar on sheltered slopes.Below the snow surface, several persistent weak layers make up a complex snowpack which is slowly beginning to show signs of improving. In the top 150-200 cm of the snowpack, two surface hoar layers buried in January can be found. Expect to find one or other of these on all aspects and elevations.Deeper in the snowpack (200-250 cm) is a facet/crust/surface hoar layer from December that is most prevalent at treeline and below.Near the base of the snowpack is a crust/facet combo from late November.

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