Lawinenlagebericht

Purcells

Feb 28 – 29, 2020Avalanche Canada
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Lawinengefahr

Sun
Mon
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Kernpunkte

A warming trend has the potential of activating a couple weak layers buried in the snowpack. Use added caution while travelling, particularly where snow overlies a layer of surface hoar and in rocky, shallow snowpack areas.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Around 10 to 30 cm of recent snow has been blown around by recent wind. This snow may be sitting on a layer of surface hoar found at all elevations and on all aspects. The recent snow has been touchiest where wind affected. Once enough snow accumulates and forms slab properties, this problem may become widespread. The western half of the region may be reaching a threshold amount of snow to be able to trigger the surface hoar and a warming trend could help build slab properties across the region.

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely - Possible
    Größe
    2–3.5

    Weak snow at the bottom of the snowpack continues to pose a deep persistent slab avalanche problem. Treat wind scoured, rocky, shallow terrain as suspect. Also avoid big alpine slopes that are threatened by cornices overhead. A warming trend has the potential of waking up this layer on Friday.

Confidence

High -

Weather Forecast

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

FRIDAY: Partly cloudy with isolated flurries, accumulation 1 to 3 cm, light to moderate southwest wind, alpine temperature -5 C, freezing level 1700 m.

SATURDAY: Cloudy with snowfall, accumulation 5 to 10 cm, moderate southwest wind, alpine temperature -9 C, freezing level 1300 m.

SUNDAY: Morning snowfall then a mix of sun and cloud, accumulation 1 to 3 cm, light northwest wind, alpine temperature -10 C.

Avalanche Summary

A few small (size 1 to 1.5) wind and storm slab avalanches were triggered by humans on Wednesday. They occurred on northerly to easterly slopes around 2300 m and the slabs were generally 20 to 30 cm thick. A few of the avalanches released on the surface hoar layer described in the Snowpack Summary, which occurred in the western (deeper) half of the region.

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 may sit 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.

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