Bulletin d’avalanche

Lizard-Flathead

Feb 21, 2018Avalanche Canada
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Archivé · expiré 9 years ago

Danger d’avalanche

Thu
Fri
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Points saillants

Wind slabs still linger in lee features at higher elevations. Watch for signs of avalanche activity and locally unstable snow, such as whumpfing and shooting cracks.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2.5
    Wind slabs formed during last weekends storm still linger in lee features. Be cautious of overhead exposure on solar aspects when the sun is out.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    2–4
    Several weak layers are lurking in our snowpack. Although the probability of triggering them is relatively low, they would produce avalanches with high consequences. Watch out for thin spots in the snowpack, where it is more likely to trigger them.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

WEDNESDAY: Mostly sunny, moderate westerly winds, alpine temperature near -13 C, freezing level below valley bottom.THURSDAY: Partly cloudy, light easterly winds, alpine temperature near -12 C, freezing level below valley bottom.FRIDAY: Mostly sunny with increasing cloudiness, light to moderate southwesterly winds, alpine temperature near -11 C, freezing level below valley bottom.

Avalanche Summary

On Monday, a few small slab avalanches (size 1 to 1.5) were reported on northerly to westerly aspects, triggered by small cornice chunks and skiers.  They were 10 to 30 cm deep and in treeline and alpine terrain.Avalanche activity may slow down with a period of cold, clear weather that is expected to persist this week.  However, the sun is packing more of a punch as the days get longer and it will warm the snow surface on solar aspects if clear skies prevail. Watch for steep sunny slopes due to the sun’s influence, lee features for reactive wind slabs, and be extra cautious near thin spots and shallow snow pack areas where triggering a deeper weak layer is more likely.  There is a lower probability of triggering a deeper layer than in previous weeks, but the consequence would be very high if one was triggered.

Snowpack Summary

Around 50-80 cm of recent snow with strong winds have created wind slabs in direct lee features. On steep solar aspects, a thin sun crust exists.  These overly a layer of surface hoar, graupel, and a melt-freeze crust buried mid-February.  The melt-freeze crust exists up to 1700 m in elevation.Deeper in the snowpack, a widespread weak layer from mid-December composed of facets, crusts, and surface hoar is 120-160 cm deep. Also, a rain crust with sugary facets buried in late November is near the base of the snowpack. If triggered, these weak layers could produce large, destructive avalanches with high consequences.

Régions couvertes