Lawinenlagebericht

Northwest Mountains

Crested Butte Avalanche Center
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Lawinengefahr

Sun
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist 2 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Stay cautious of previously drifted slabs about a foot thick below leeward ridgelines and in concave gullies, such as this skier-triggered avalanche yesterday.  Dry loose avalanches that can gouge to the ground through weak facets are easy to trigger in wind-protected, shady slopes steeper than 35 degrees.    Santa's video from the field yesterday shows what these problems will feel like under your feet or machine. 

Lawinenprobleme

  • Persistent Slabs

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

    Since 12/9, several northwest-to-southwest wind events formed slabs around a foot thick. These wind-drifted slabs are most commonly found at higher elevations below leeward ridgelines and rollovers on east to northeast-facing terrain. They can also be found around the northern half of the compass in a few concave terrain features that collect drifting snow, such as gullies. These slabs are often hard and difficult to trigger, but some formed over weak, faceted snow that is slow to heal, making for variable feedback.  Assess recent wind-loading patterns and avoid previously wind-loaded terrain features, especially in high-consequence terrain.

  • Loose Dry

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–1.5

    In terrain that has been protected from the sun and wind, the snowpack is growing increasingly weak and cohesionless, causing easily-triggered dry loose avalanches in terrain steeper than 35 degrees.  These point-release instabilities are relatively small and easy to recognize. Still, they can spell trouble by pushing you into trees, rocks, or gullies, especially in long, steep terrain where they will gouge to the ground and gain more volume.  Use sluff management techniques or move to less consequential, lower slope angles to manage the problem. 

Avalanche Discussion

Despite the dry and mild weather this week, our snowpack remains relatively stagnant.  Where the snow surface is soft (most commonly below 11,000' on the north half of the compass), the snowpack continues to gradually get weaker with each day of our prolonged dry spell.  In both zones, observers report sluffs gouging to the ground, with "noteworthy speed and distance" once they get moving (ex. Snodgrass, Schuylkill Ridge, Axtell, Emmons). Two people have been caught and carried in these avalanches near Marble, one last week and one yesterday. Unlike the sluff management you see in ski movies, the harsh reality today is that one good ski cut on a 40-degree slope often forces you to sidestep through the rocks and grass left behind by the full-depth sluff.  Good for the bloopers reel.

On the other hand, the persistent slabs that formed from a series of wind transport last week are also not improving much.  That's because a) they typically formed over shallow, weak bed surfaces, and temperature gradients in a thin snowpack prohibit these layers from bonding, and b) they are commonly hard slabs, which means they aren't decaying quickly like soft slabs do when the facet factory turns on.  Recent observations of triggered avalanches and collapses in both zones demonstrate this ongoing issue (ex. Schuylkill Ridge, Upper Cement). Slopes that saw wind erosion are your safer (and typically softer) option at higher elevations.  The variable snow is not quite ski movie material either, but hey, now we are really building a good bloopers reel. Our field observations and observed avalanche activity since the wind events started suggest slabs are generally more common and thicker north and west of town, where winds have had more snow available to transport. However, both zones have problematic slopes if you find a terrain feature that saw productive wind loading rather than erosion.  

Events:  Our first Fireside Chat of the year is this Sunday (12/22) at 6 p.m. at the Eldo.  Andy Sovick(Beacon Guidebooks/OnX Maps) will chat about Maps and Tour Planning.  These events are free and open to all.

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