Avalanche forecast

Purcells

Nov 30 – Dec 1, 2015Avalanche Canada
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Avalanche danger

Wed
Thu
Alpine
No rating
Treeline
No rating
Below
No rating
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Highlights

A big change in the weather is headed our way. Tuesday is the probably going to be the last day you can confidently get after it in big terrain for a while.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–3
    Previously strong north winds formed wind slabs that extend from treeline to just below ridge crest. Most of these wind slabs are probably old, tired and hard to trigger, but there may be a few that remain sensitive to human triggering.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    3–6
    We suspect that this is really only a problem on high elevation north facing features where weak faceted snow *may* exist at the base of the snowpack.

Confidence

Poor - Due to the number of field observations

Weather Forecast

Bottom Line: The weather is changing, the inversion should be cleared out by Tuesday morning. The coast will likely get hammered as a digging upper trough makes landfall over the next few days. Some of the snow and southerly winds associated with this event are expected to spill over into the Purcells. At this point amounts and timing are too dynamic to pin down, but the region should see 1 to 3cm of snow Tuesday night, with an additional skiff of snow Wednesday. Strong SW winds are expected throughout the region beginning Tuesday night. The freezing level should remain at valley bottom through Tuesday night. Its expected to climb to around 1500m Wednesday before returning to valley bottom Wednesday night. The pattern looks similar for Thursday with the freezing level once again rising to around 1500m. For detailed mountain weather information visit: avalanche.ca/weather.

Avalanche Summary

The only recent avalanche activity reported has been loose snow sluffing from steep north facing terrain.

Snowpack Summary

The snowpack is extremely variable at this time. Wind scoured north facing slopes exist at treeline and above from the recent strong winds associated with the arctic front. South facing slopes have wind slabs at tree line and above and may be hiding surface hoar from the previous spell of cold clear weather. Surface facetting has been observed in the region as a result of the recent cold weather and clear skies, and surface hoar up to 20mm has been reported in sheltered locations below treeline. There are a number of surface hoar layers now buried in the snowpack, but at present they appear to be unreactive, the most recent having been buried on Nov 24th. In shallow snowpack areas, especially on northern aspects, there may be a weak facetted layer at the base of the snowpack. Recent warming at upper elevations has likely changed the snowpack on all aspects, especially those facing south where you can expect a suncrust above 1500m.

Regions covered