Avalanche forecast

South Columbia

Feb 17 – 18, 2016Avalanche Canada
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Avalanche danger

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

Forecast new snow amounts and freezing levels are uncertain, due to weather models variability. If your area gets more snow than I have forecast, these danger ratings may be one level too low.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–4
    Forecast new snow and wind are expected to  increase the likelihood of triggering the storm slab at the crust interface down 40-70 cm. Expect new windslabs to develop during the stormy weather overnight and Thursday.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–3
    Warm temperatures and high freezing levels may increase the likelihood of triggering loose wet avalanches in steep terrain at and below treeline

Confidence

Moderate - Freezing levels are uncertain

Weather Forecast

Moderate snow (5-10 cm) overnight with light southerly winds and freezing levels at about 1600 metres in the south and closer to 1000 metres in the north. Another 8-12 cm during the day on Thursday with increasing southwest winds and freezing levels up to about 1800 metres in the south. On Friday, expect light-moderate snow, light winds, and a chance of broken skies in the west of the region. Freezing levels should rise up to about 1400 metres during the day and then fall to valley bottoms by Saturday morning. Scattered cloud with light southerly winds on Saturday, freezing level rising again to at least 1400 metres.

Avalanche Summary

On Tuesday there were several skier accidental avalanches up to size 2.0 that released on the storm slab/crust interface. Skier controlled storm slab avalanches up to size 1.5 were mostly on east aspects at treeline. On Monday we had reports of natural wind slab and storm slab avalanches up to size 3.0 and accidentally triggered slab avalanches up to size 1.5.

Snowpack Summary

Recent new snow and wind have developed storm slabs that are 40-70 cm deep. These storm slabs are sitting on a buried melt-freeze crust on east thru west aspects in the alpine, and on all aspects at treeline. In some areas there is a weak layer of surface hoar at the interface between the storm snow and the crust. Moderate winds have created areas of wind slab in the lee of west or southwest winds that may be close to a metre deep. Wind slabs in motion may trigger the storm slab on the crust and result in wide propagations and very large avalanches. The bond between the recent storm snow and the crust is variable across the region, east thru southeast aspects have been the most reactive over the past few days. Surface hoar buried in early January now lies up to 200cm below the surface and has become less of a concern. Possible triggers for this deep and destructive layer include a large cornice fall or significant warming.

Regions covered