Avalanche forecast

South Rockies

Jan 20 – 21, 2013Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
2 · Moderate
Treeline
1 · Low
Below
1 · Low
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Highlights

Low danger doesn't mean no danger. Be cautious around steep sun exposed slopes Monday afternoon.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–4
    Watch for the odd tired old wind slab just below ridge crest or lee of a midslope feature like a rib or rock outcropping.  Sensitivity may increase slightly on slopes receiving direct sun Monday afternoon.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2
      Loose snow avalanche activity will likely pick up Monday afternoon on slopes receiving direct sun.

Confidence

Good - Forecast snowfall amounts are uncertain on Wednesday

Weather Forecast

Monday: Inversion. Freezing level at surface. Above freezing layer from 1500m – 2500m. Ridgetop winds strong NW. Treeline winds mod NW. No precip. Scattered cloud, clearing in the afternoon.Tuesday: Should be the last inverted day. Freezing level at surface. Above freezing layer from 1500m – 3000m. Ridgetop winds Mod NW. Treeline winds light W. No precip.  Broken cloud cover for most of the day.Wednesday: Freezing level at valley bottom.  Snowing all day Wednesday with total daytime accumulations in the 5 – 10 cm range. Snowfall tapering overnight. Ridgetop winds initially strong W, steadily increasing to extreme NW by late afternoon.

Avalanche Summary

Activity has been limited to size 1 loose snow avalanches on slopes receiving direct sun.  Interestingly, a glide avalanche was observed on Mt. Fernie Saturday. 

Snowpack Summary

Intense recent winds have redistributed snow and created large cornices. The snow surface is now a mix of sastrugi, hard slab and soft slab in open areas. While the effects of the wind were dramatic, the sensitivity of the wind slab to triggering is decreasing. With the warm temps, slopes receiving direct sun are moistening in the afternoon. Surface hoar is continuing to form in protected areas too with recent observations of 10cm crystals. Below this around 50cm of settled snow rests on a myriad of old surfaces (January 4th interface) that include sun crust on steep south and west facing terrain, surface hoar in sheltered locations at treeline and below and facets everywhere else. Tests on this interface are still yielding sudden planar results, but the overlying slab has settled significantly and there haven't been any reported avalanches on this layer in some time now.  There are some reports of glide cracks on Mt Fernie, these mysterious phenomena should be given a wide berth.

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