Avalanche forecast

Purcells

Mar 4 – 5, 2016Avalanche Canada
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Archived · expired 11 years ago

Avalanche danger

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

Forecast new snow and wind are expected to continue to allow for easy triggering of storm slabs.

Avalanche problems

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    1–4
    Cornices are large and fragile and may continue to grow with forecast new snow and wind. Warm temperatures and high freezing levels may result in natural cornice falls.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–5
    The February 10th surface hoar layer is buried down about 60 cm in most areas. High freezing levels and continued loading from new snow and wind may increase the likelihood of triggering this persistent weak layer.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3
    Storm slabs continue to develop with new snow and wind. Storm slabs may be sitting on a weak layer of surface hoar, a crust, or a crust/surface hoar layer that allows for easy triggering.

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

Freezing levels remaining above 1500 metres overnight with moderate southwest winds. 3-5 cm of new snow and moderate southwest winds expected during the day on Saturday with freezing levels rising to 2000 metres. Another 5-10 cm of new snow on Sunday with moderate winds and freezing levels above 1500 metres. A weak ridge should drop freezing levels to valley bottoms by Monday morning, before broken or scattered cloud allows the sun to bring the freezing level back up to 1500 metres during the day.

Avalanche Summary

No new natural avalanches reported on Thursday. One skier remote size 2.0 storm slab avalanche was reported from an east aspect in the alpine. Explosives triggered avalanches up to size 2.5 on various aspects. One new natural cornice fall was reported on Friday.

Snowpack Summary

15-30 cm of recent storm snow is bonding poorly to a melt-freeze crust on previously sun-exposed slopes and lower elevation terrain, and/or a layer of surface hoar on shady and sheltered slopes at treeline elevations. Thicker and touchier fresh wind slabs are lurking in exposed lee and cross-loaded terrain. The surface hoar and/or crust layer buried in mid-February is now down 40-70cm. This layer was less reactive over the past week with cooler temperatures. Large weak cornices remain concerning and have recently triggered persistent slabs on slopes below. The early January surface hoar/facet layer is typically down 70-120cm. Triggering an avalanche on this layer has become unlikely but it still has isolated potential to produce very large avalanches with a heavy trigger. In general, the lower snowpack is well settled and strong, apart from some thin snowpack areas where basal facets exist.

Regions covered