Avalanche forecast

Purcells

Mar 9 – 10, 2014Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Warming temperatures and Solar radiation will play a leading role in the avalanche hazard in the coming days. Pay special attention to large ripe cornices !

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–4
    Recent storm snow is settling into a dense slab that overlies a variety of weak layers. Warm temperatures will set the stage for natural and rider triggered avalanches, use caution in recently wind loaded terrain. Cornice hazard is also a concern.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–5
    Additional loading and rising temperatures make the possibility of triggering deep layers more likely. A cornice failure could produce an avalanche that might step down to buried weak layers.

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

Synopsis: An intense frontal system with subtropical moisture plowed it's way across the Province in the last 24 hours, pushing freezing levels above 2000 metres in some parts of the forecast area. The bulk of the moisture will be out of the forecast area later today.Tonight: Localized flurries are possible, The southern part of the forecast area may see light to locally moderate precipitation this evening. Freezing level around 1700m. Moderate to strong west winds.Monday: Mix of sun and clouds, possibility of flurries, moderate to strong winds at ridge tops, freezing level may climb to around 1400m.Tuesday: Sunny with cloudy periods, no precipitation in the forecast, freezing around 1400m. winds from the west, light gusting to moderate.Wednesday: Sunny with cloudy periods, freezing level rising to 1900m. Light ridge top winds.

Avalanche Summary

Storm slab avalanches continue to be reported running naturally. Most of the storm snow avalanches are size 1.5-2.0, however one was reported to be size 3.0 where the storm slab is now 80 cm thick. Explosives control released some large avalanches down to the early February persistent weak layer. There were also a couple of accidentally triggered storm slab avalanches, one that buried a sledder on a northwest aspect in the alpine. Neighboring forecast regions have reported large avalanches initiating in the new storm snow, then stepping down to deeper layers, some  running full path to the ground.  The South Columbia's reported a size 4.5 on a south aspect than ran more that 1500 vertical metres.

Snowpack Summary

Recent snowfall amounts have been highly variable throughout the region. In some deeper snowpack areas 80 to 100cm of storm snow overlies a weak surface hoar layer that has been preserved in sheltered areas. A buried sun crust exists on solar aspects and and there are wind slabs in exposed terrain. On lee slopes these accumulations have been pushed into much deeper deposits by generally moderate southwest winds. Warming has added cohesion to the slab and wider propagations can be expected. At lower elevations rain has moistened snow surfaces, and we might see loose wet avalanches on solar aspects. There is ongoing concern for a mix of weak surfaces which were buried on February 10th. This persistent interface lies between 60 and 160cm below the surface, and includes surface hoar, well developed facets and a mix of hard surfaces which remain widespread at all aspects and elevations. In some areas destructive avalanches are still a very real concern with ongoing reports of natural triggering, whumpfing and sudden/easy snowpack test results. The mid and lower snowpack are generally strong and well consolidated. Weak basal facets exist in many areas, but triggering now is unlikely.

Regions covered