Avalanche forecast

North Columbia

Jan 5 – 7, 2020Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Continuing snowfall and wind are out-pacing the snowpack's ability to adjust. Stay vigilant with simple terrain choices as this pattern continues.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2.5

    Strong winds with ample snow for transport over the past 48 hours have formed touchy wind slabs in exposed areas, particularly near ridge features. 

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2.5

    50-90 cm of snow has accumulated in the past week over a layer of surface hoar from late December. This layer has demonstrated reactivity past its due date as a storm slab interface and has produced large avalanches across aspects and elevations with incremental loading from new snow and wind. A few of these avalanches were human-triggered remotely from adjacent slopes.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Sunday night: Cloudy, 10-20 cm of snow, moderate west wind with strong gusts, alpine temperature -11 C, freezing level dropping from 1000 m to valley bottom.

Monday: Mostly cloudy, isolated flurries with trace accumulations, light to moderate southwest wind, alpine high temperature -6 C.

Tuesday: Cloudy, 15-25 cm of snow overnight and throughout the day, moderate south wind, alpine high temperature -6 C.

Wednesday: Cloudy, 20-30 cm of snow overnight throughout the day, moderate west wind, alpine high temperature -6 C.

Avalanche Summary

Several human-triggered wind slabs were reported at treeline and alpine elevations on leeward features on Saturday. These avalanches broke 10-40 cm deep and were small in size (size 1-1.5). Additional snowfall and wind transport overnight may increase the size of these slabs on Monday.

Observers also reported large (size 2-3) avalanches breaking on a layer of surface hoar from late December on a variety of aspects and elevations from natural, human, and explosive triggers on Saturday and into Sunday. A few of these avalanches were triggered remotely (i.e. from a distance). 

Snowpack Summary

The most recent snow has been redistributed by strong southwest winds in exposed areas, loading lee features with stiffer, more reactive slabs. 

Over the past week, a total of 60-100 cm of snow has fallen burying a weak layer of feathery surface hoar and a hard melt-freeze crust on sun-exposed aspects. This layer has demonstrated reactivity past its due date as a storm slab interface, and it continues to produce large avalanches across aspects and elevations.

There are a couple more deeply buried weak layers, including a surface hoar layer from mid-December and a facet/crust layer from late November. Despite the significant load from recent snowfall and wind as well as a widespread, large natural avalanche cycle, avalanches have not been observed stepping down to these layers. 

Terrain and Travel

  • Avoid freshly wind loaded terrain features.
  • Be alert to conditions that change with elevation and wind exposure.
  • Be aware of the potential for large avalanches due to the presence of buried weak layers.
  • Remote triggering is a concern, watch out for adjacent and overhead slopes.

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