Avalanche forecast

Purcells

Mar 15 – 16, 2015Avalanche Canada
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Archived · expired 12 years ago

Avalanche danger

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

Hazard ratings reflect conditions in the south of the region where heavy snowfall is expected overnight.Touchy storm slabs have formed at higher elevations. Use a very conservative approach and avoid avalanche terrain during periods of heavy loading.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–4
    Storm slabs continue to develop in the south of the region. These slabs sit over a weakness from mid-February and is reactive to human-triggering.  Thicker touchy wind slabs can be found in leeward terrain features in wind exposed terrain.

Avalanche Summary

Observations were limited on Saturday due to the storm conditions but ski cuts produced size 1 slab avalanches. On Monday, touchy storm slabs are expected in the alpine and possibly at treeline, especially in the south of the region. There is some uncertainty regarding the distribution of these storm slabs but they could be widespread. Thicker winds slabs associated with the storm are expected in leeward features and are the biggest concern for Monday.

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

The south of the region can expect another 15-30mm of precipitation Sunday overnight with freezing levels around 1500m and moderate alpine winds. A ridge of high pressure should keep the region dry for the next two days expect lingering flurries on Monday morning. A mix of sun and cloud is expected for the north of the region on Monday while the south will be mainly overcast. Alpine winds should be light and freezing levels should reach around 1800m in the afternoon. Overnight the freezing levels should fall close to valley bottom. On Tuesday, a mix of sun and cloud is expected with light alpine winds and freezing levels reaching around 2000m. Light flurries or showers are possible for Wednesday.

Snowpack Summary

At higher elevations, new snow sits over a variety of surfaces including moist snow, crusts, wind affected surfaces, and/or old wind slabs which may still be reactive. Rain has soaked the upper snowpack to around treeline elevation. In the alpine, strong winds during the storm have redistributed the new snow into wind slabs in leeward terrain features. Prior to the storm, 10-30cm of snow was sitting over a weak facet/crust layer that was buried in mid-February. This layer has been quite reactive recently and may increase the likelihood of triggering a storm slab. The late-Jan crust/surface hoar layer (around 70cm deep) and the mid-January surface hoar (around 1m deep) have been dormant for several weeks.

Regions covered