Avalanche forecast

Purcells

Feb 20 – 21, 2015Avalanche Canada
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Avalanche danger

Sun
Mon
Alpine
2 · Moderate
Treeline
1 · Low
Below
1 · Low
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Highlights

Watch for deep and touchy pockets of wind slab in wind exposed terrain.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–3
    Pockets of touchy wind slab may still be sensitive to triggering in lee and cross-loaded terrain. Some areas could see these slabs build if there is a decent amount of snow on Saturday with moderate winds. 

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–6
    Buried persistent weaknesses are largely dormant but could still be triggered by a large load (i.e. cornice fall) or from areas with a shallow or variable snowpack.

Confidence

Good

Weather Forecast

The ridge of high pressure rebuilds and should result in clearing skies in most parts of the Province. However, there is a weak cold front sliding in from the east that could bring cloud and light snow to parts of the Southern Interior (particularly the east side of Purcells). By Sunday all regions should be enjoying sunny skies. The freezing level on Saturday is 500-1000 m and it bumps up a couple hundred metres each day. Ridge winds are light gusting to moderate from the NW to NE.

Avalanche Summary

Avalanche activity has gradually tapered off throughout the week. On Thursday explosive control work on steep North and East facing slopes only resulted in loose snow sluffs. Earlier in the week there were reports of natural and explosive triggered cornice falls and slabs, typically size 2-3 and all from alpine terrain.

Snowpack Summary

A light dusting of new snow covers the previous variable snow surface of crusts, surface hoar, dry facetted snow, or wind affected snow depending on aspect and elevation. Thin new wind slabs are likely in exposed lee terrain, and cornices remain large and weak. The 'Valentine's Day' crust is thick and supportive below 2100 m. The late-Jan crust/surface hoar layer is 1-2 m deep in the west, and can be found within the upper metre of the snowpack further east. It is variably reactive in snowpack tests and still the main concern in many areas. The mid-January surface hoar, deeper again, remains problematic in some areas. The mid-December and mid-November weak layers of crusts and facets can still be found near the bottom of the snowpack, particularly in shallower eastern parts of the Purcells.

Regions covered