Avalanche forecast

South Coast

Mar 11 – 12, 2014Avalanche Canada
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Avalanche danger

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

Strong solar radiation and high freezing levels may elevate hazard and could trigger natural avalanche activity on south facing slopes during the day.

Avalanche problems

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–4
    Cornices may become weak during daytime warming.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–5
    There are a couple of old weak layers buried between 60 and 150 cm deep. It has become much less likely to trigger these but storm slab avalanches or cornice falls may step down to one of these layers.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    2–5
    Weaknesses may still exist within or under the storm snow from the weekend. Old wind slabs in exposed NW through E facing terrain are being more stubborn but may still be a concern. Use increased caution during the heat of the afternoon.

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

High pressure conditions will remain for Wednesday and Thursday but a pulse of moisture may cross the region late Wednesday. A more organized system is expected for the S Coast on Friday but it is difficult to tell how far inland it will push. It may result in light flurries or rain showers. Wednesday: Mostly sunny, scattered flurries possible in the evening 0-2cm, freezing level 600-800m overnight, ~2000m afternoon, ridgetop wind 20-40 km/h SWThursday: A mix of sun and cloud, freezing level 800-1200m overnight, ~1700m afternoon, ridgetop wind light SWFriday: Flurries or rain 2-8mm, freezing level 1000-1200m overnight, ~2000m afternoon, ridgetop wind 20-40 km/h SW

Avalanche Summary

During the storm on the weekend, we saw widespread natural slab avalanche activity. Most of this activity involved the storm snow itself but there were numerous avalanches which stepped down to the early-March weak layer or possibly even the February weak layer. Now that the storm is over, natural activity is tapering off but large avalanches are still possible. On Monday, we received reports of slab avalanches up to size 2.5, both natural and human-triggered. At lower elevations, loose wet sluffing from steep solar aspects is being reported.

Snowpack Summary

During the storm on the weekend, storm slabs and wind slabs formed at higher elevations across the regions.  These are generally becoming more stable but isolated avalanches are still occurring.  High freezing levels and solar warming may destabilize the upper snowpack on Wednesday afternoon.Coquihalla and south: Recent mild temperatures have resulted in rain to ridgetop in many areas. It's likely that the upper snowpack below 1700-1800 m was saturated and/or contains several melt-freeze crusts. The early March melt-freeze crust is down 60-100 cm depending on elevation.  Duffey Lake and north: The early March melt-freeze crust is down 60-80 cm on north aspects up to 1800 m and south aspects up to 2200 m. The mid Feb weak layer is generally now found down 90-130 cm. Freezing levels were lower in this part of the region and the snowpack has generally been more reactive than the south.

Regions covered