Avalanche forecast

Purcells

Apr 20 – 21, 2013Avalanche Canada
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Archived · expired 13 years ago

Avalanche danger

Mon
Tue
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

The Public Avalanche Forecasts and Danger Ratings will come to an end on Tuesday. General spring messaging will be found under the Forecast Details tab.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–4
    Touchy wind slabs exist on lee slopes at treeline and above. Cornices have grown very large, so be aware of overhead hazards and stay back on ridgelines.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    1–6
    A weak interface buried in the upper metre of the snowpack can create surprisingly large avalanches. It's been reactive in nearby regions, and remains a concern with professionals. Be cautious in steep, alpine terrain.

Avalanche Summary

On Friday, numerous size 1.5-2 wind slab avalanches were skier triggered. All of which were from 35-40 degree slopes on NE aspects above 2100 m. All of these avalanches failed within the recent storm snow interface approximately 30 cm down, and the early April interface around 80 cm down. One of these was remotely triggered from 15 m away, size 2. 

Confidence

Fair - Due to limited field observations

Weather Forecast

The Interior will remain under a cool, dry North-West flow through to Tuesday. A slow warming trend will persist through the end of next week.Sunday: Scattered-broken cloud cover, allowing some sunshine through.  Ridgetop winds will blow light from the North. Freezing levels 1100 m and falling to valley bottom overnight.Monday/Tuesday: Mostly clear, sunny skies. Ridgetop winds will blow light from the NW. Freezing levels 1800 m in the afternoon.

Snowpack Summary

Up to 20 cm of new snow overlies a variety of old snow surfaces. These consist of melt-freeze crusts, buried surface hoar and surface facets. Touchy wind slabs exist on lee slopes and behind terrain features. Cornices on ridgelines have grown large, and pose a threat to slopes below.Deeper in the snowpack a weak interface buried in early April is down about 60-120 cm and consists of a crust and surface hoar. Earlier this week, very large avalanches were reactive on this interface in neighboring regions. The bond may be getting stronger, but I would still use caution and be suspicious of large, steep upper elevation slopes.

Regions covered