Lawinenlagebericht

Northwest Inland

Feb 2 – 3, 2013Avalanche Canada
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Archiviert · abgelaufen 14 years ago

Lawinengefahr

Mon
Tue
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–5
    New snow and strong shifting winds will build touchy wind slabs that are likely found behind terrain breaks such as ridges and ribs. Hollow sounds and cracking snow is a good indicator of unstable snow.

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–5
    Buried beneath the new snow sits a surface hoar/crust/facet weakness. This may be sensitive to rider triggers in steeper sheltered terrain or over convex rolls, especially at treeline and below treeline elevations.

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely - Possible
    Größe
    2–6
    A deeply buried weak layer near the base of the snowpack could be triggered by large loads such as a cornice collapse or from a thin-spot trigger point.

Confidence

Poor - Due to variable snowpack conditions

Weather Forecast

Sunday: A Pacific frontal system moves in bringing moderate precipitation amounts (10-15 mm). Ridgetop winds blowing strong from the SW. Alpine temperatures near -4.0 and freezing levels falling to 500 m. Monday: A trailing warm front moves onto the region bringing continued moisture and wind. Ridgetop winds will be strong from the SW.  Alpine temperatures -6.0 and freezing levels falling to valley bottom. Tuesday: Unsettled conditions prevail with mix of sun and cloud and no significant precipitation. Ridgetop winds will be light from the South. Alpine temperatures near -7 and freezing levels will rise to 800 m.

Avalanche Summary

Natural sluffing from steep terrain features.On Thursday, a remote triggered slab avalanche size 2.0 initiated 50 m away from the skier at treeline elevation. Another report of a size 2.0 slab avalanche (skier triggered) also occurred. Both incidents were at 1200-1300 m on North aspects with crowns 50-60 cm deep, 30-40 m wide, and running up to 150 m in length.

Snowpack Summary

Touchy wind slabs have built on lee slopes (N-SW) and behind terrain features likes ribs and ridges. Up to 50 cm buried a variety of old surfaces including old wind slabs, scoured thin slopes, crusts and surface hoar. This interface has shown reactivity to rider triggers, especially around treeline and below treeline elevations. Warmer temperatures have promoted some settlement and consolidated the recent snow into slab-like characteristics. With little observations from the field it's hard to get a good handle on how widespread this layer is. I stress the importance to dig down and test weak layers. Become familiar with the snowpack in your neck of the woods.The average snowpack depth at treeline is near 100 cm but remains quite inconsistent across the region. A strong mid-pack currently overlies a weak base layer of facets/depth hoar. Triggering of this basal weakness may still be possible from thin spots, rocky outcrops or under the weight of larger triggers such as cornice fall and larger amounts of new storm snow.

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