Lawinenlagebericht

Purcells

Mar 16 – 17, 2020Avalanche Canada
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Lawinengefahr

Wed
Thu
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

Expect an upward swing in temperatures as the freezing level rises on Monday. This shift in temperature may result in a rise in the likelihood of triggering persistent slab avalanches. Be especially cautious underneath steep sun exposed slopes and around rock outcrops.

Lawinenprobleme

  • Wind Slabs

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

    Moderate to strong northeast and east wind formed wind slabs at all elevations which might be reactive to human triggers. 

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible - Likely
    Größe
    1.5–2.5

    A weak layer of surface hoar sits 50-100 cm deep, within the range for human-triggering. Over the past week, large human-triggered avalanches have released on this layer.

  • Deep Persistent Slabs

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

    Weak facetted snow at the near the base of the snowpack continues to be a concern. Treat wind-scoured, rocky, shallow terrain as suspect and avoid big alpine slopes that are threatened by cornices overhead. 

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

SUNDAY NIGHT: Mainly clear, light northeast wind, alpine temperature -8 C.

MONDAY: Clear skies, light northwest wind, alpine temperature -1 C, freezing level 1800 m.

TUESDAY: Mix of sun and cloud, light northwest wind, alpine temperature -2 C, freezing level 1700 m.

WEDNESDAY: Mix of sun and cloud, light northwest wind, alpine temperature -4 C, freezing level 1500 m.

Avalanche Summary

There were reports of a few natural wind slab avalanches on the weekend size 1.5 to 2.5 on north and southeast aspects in the alpine. 

Snowpack Summary

Recent moderate to strong northeast and east wind has redistributed the snow and formed wind slabs at all elevations. New snow from last week may sit on a weak surface hoar layer and a sun crust on steep solar aspects. 

A weak layer of surface hoar buried February 22 may be found 50-100 cm deep. It may sit over a crust on solar aspects. This persistent weak layer will likely remain a problem until there is a substantial change in the snowpack. Read more about surface hoar on our forecaster blog.

Deeply buried facets lurk near the bottom of the snowpack. This layer has been responsible for sporadic deep persistent slab avalanches, usually triggered from shallow, rocky start zones.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.
  • Minimize exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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