Avalanche forecast

South Coast Inland

Dec 21, 2018Avalanche Canada
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Archived · expired 8 years ago

Avalanche danger

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

The sun should shine on Friday, showcasing snow distribution and avalanche activity from Thursday's storm. Be wary of the bonding of all the recent snow, especially in lee terrain features near ridges, where snow deposits will be deep.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3
    A weak layer buried approximately 120 cm has the potential to produce large avalanches. This layer is likely most problematic in the north section of the region and around treeline elevations.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–2.5
    Around 30 to 40 cm of snow fell on Thursday with associated strong southerly winds. The deepest deposits will be in lee terrain features near ridges. Expect this recent snow to be reactive to human traffic.

Confidence

Moderate - Due to the number of field observations.

Weather Forecast

THURSDAY NIGHT: Cloudy, freezing level dropping from 1000m to below valley bottom. FRIDAY: Partly cloudy, moderate northwest winds, alpine temperature -12°c, freezing level below valley bottom. SATURDAY: Cloudy with light snowfall, accumulation 5cm, moderate southwest winds, alpine temperature -7°c, freezing level below valley bottom. SUNDAY: Cloudy with snowfall, accumulation 5 to 10cm, moderate southwest winds, alpine temperature -5°c, freezing level 1000m.

Avalanche Summary

Natural storm slab avalanche cycles have occurred during each storm within the past week (see description and photos here). It is likely that a natural cycle occurred again on Thursday during the storm. Clearing skies on Friday should allow for views of previous avalanche activity.

Snowpack Summary

Around 30 to 40cm of snow fell in the region on Thursday with associated strong southerly winds. Deeper snow deposits are likely in the lees of terrain features. This sits on around 1 to 2m of storm snow that has fallen in the past two weeks. Below 1500m, Thursday's precipitation mostly fell as rain. In the north portion of the region, a weak layer of facets and surface hoar lies below all this storm snow, around 120cm deep. The weak layer appears most prominent around treeline, up to 2000m. While the layer is likely gaining strength, field observations show that slab avalanches remain possible on this layer where it exists. Near the base of the snowpack, a crust exists with weak and sugary facets beneath it. This could potentially still be of concern in high north-facing aspects where the snowpack rests on very smooth ground cover.

Regions covered