Avalanche forecast

Northwest Coastal

Mar 23 – 24, 2014Avalanche Canada
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Avalanche danger

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

Hazard could be higher than forecast on solar aspects in the afternoon. Cornices are growing large, and scary-looking and require careful consideration.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–5
    Activity on the March and February weak layers has slowed down, but these layers are still subject to triggering with the right load, and will produce a very large destructive avalanche

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–4
    Considerable new snow has been redistributed onto lee slopes. This recent storm snow is sitting on a variety of older weak surfaces. Conservative terrain choices are critical right now. Rider triggered avalanches are definitely possible.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3–6

Confidence

Fair - Forecast snowfall amounts are uncertain on Monday

Weather Forecast

Synopsis: The high pressure ridge in the interior of has cooled things down a bit, but will recede with the oncoming Pacific frontal system.Tonight: Cloudy, no precipitation in the forecast, freezing level around 100 metres, winds light to moderate, from the north west.Monday: Cloudy with flurries. Forecast models differ on precipitation amounts for Monday night freezing level around 400 metres, winds light to moderate from the north. .Tuesday: Cloudy with a trace of precipitation in the forecast, freezing level at 600 metres, winds light, from the north.Wednesday: Cloudy with isolated flurries, trace of precipitation in the forecast. freezing level around 600 metres, light ridge top winds.

Avalanche Summary

No reports of avalanche activity in the forecast region from yesterday. Remember that the weak layers are still there, and rider triggering is still possible. Cornices have become quite large in some parts of the forecast region and they are definitely something to watch out for.

Snowpack Summary

The area has received 75 to 150cm of snow over the past 5 to 7 days. The recent storm snow arrived with strong winds and produced wind slabs at tree line and above and increasing the depth on the slab that now overlies the March persistent weak layer. In addition, much of the recent storm snow has fallen on a melt freeze and/or rain crusts that exist in most parts of the region below 1200 metres. This will most likely become reactive on solar aspects when the sun finally comes out.The March weak layer is a combination of hard wind-scoured slab surfaces in exposed terrain, facets and/or surface hoar in sheltered and north aspects, and sun crust on steep solar aspects. This layer is widespread throughout the forecast region and is now buried close to 150cm in most parts of the area. A late January/early February crust/facet/surface hoar combo is still showing up in snowpack tests with moderate to hard shear tests. It appears to be dormant for the time being, but a sudden increase in load, a cornice failure, or a large rainfall event could "wake up" this layer and result in a large destructive avalanche.

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