Avalanche forecast

Purcells

Feb 26 – 27, 2020Avalanche Canada
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Archived · expired 7 years ago

Avalanche danger

Fri
Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Wind slabs have been triggerable by riders in the past few days. As snowfall continues to accumulate, slabs may become surprisingly touchy where they rest on surface hoar.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Around 10 to 30 cm of recent snow has been blown around by variable wind. This snow may be sitting on top of a layer of surface hoar found at all elevations and on all aspects. On solar aspects, the surface hoar may be sitting on a melt-freeze crust, which is a particularly nasty combination. For now, the recent snow has been touchiest where wind affected. Once enough snow accumulates and forms slab properties, this problem may become widespread. This is most likely to occur first in the snowier spots in the west of the region.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–3.5

    Weak snow at the bottom of the snowpack continues to pose a deep persistent slab avalanche problem. The most recent activity has been focused around the Golden area, but wind scoured, rocky, shallow terrain can be suspect. Avoid big alpine slopes that are threatened by cornices overhead.

Confidence

High -

Weather Forecast

TUESDAY NIGHT: Partly cloudy with isolated flurries, accumulation 1 to 3 cm, moderate west wind, alpine temperature -7 C.

WEDNESDAY: Morning snowfall and afternoon clearing, accumulation 2 to 5 cm, moderate west wind, alpine temperature -8 C, freezing level rising to 1400 m.

THURSDAY: Partly cloudy with isolated flurries, accumulation 1 to 3 cm, light to moderate west wind, alpine temperature -5 C, freezing level rising to 1500 m.

FRIDAY: Partly cloudy with isolated flurries, accumulation 1 to 3 cm, light southwest wind, alpine temperature -4 C, freezing level 1600 m.

Avalanche Summary

A few small (size 1 to 1.5) wind and storm slab avalanches were triggered by skiers and naturally on Monday. They generally occurred on north to east aspects but one occurred on a southwest aspect. They were 20 to 30 cm thick and occurred at alpine elevations.

Snowpack Summary

Around 10 to 30 cm of recent snow covers a widespread layer of surface hoar (size 5 to 15 mm) that was found at all elevations and on all aspects. On southeast through southwest facing slopes, this surface hoar likely grew on a thin melt-freeze crust, which is a nasty combination. The recent snow has been blown around by variable wind, forming wind slabs at higher elevations, particularly near ridges.

The middle of the snowpack is strong. The base of the snowpack contains basal facets, which have been responsible for occasional and hard-to-predict Deep Persistent Slab avalanches in shallow rocky start zones.

Terrain and Travel

  • Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

Regions covered