Bollettino valanghe

Southeast Mountains

Crested Butte Avalanche Center
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Pericolo valanghe

Tue
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Two serious accidents over the weekend illustrate the snowpack's potential for dangerous surprises.  Feedback is becoming more sporadic, but human-triggered avalanches continue to occur daily.  A tricky layer of buried surface hoar one or two feet thick has been the culprit in much of the recent avalanche activity.  Conservative decision-making is the best strategy for handling our persistent slab problem.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2.5

    A new round of weak layers was buried on February 2nd. These weak layers consist of surface hoar and facets on most east, north, and west-facing slopes, and faceted crusts on high-elevation southerly aspects. This weak interface is now buried 1 to 2 feet on average. In the last week, there have been daily human-triggered avalanches and natural avalanche activity. This avalanche problem can be remotely triggered from flat terrain, or propagate widely across terrain features.  Shooting cracks or collapses are a clear sign of danger, but these obvious signs of instability will not always show themselves before an avalanche releases.

    There are old faceted weak layers near the ground that are more stubborn to human triggers. These dense old slabs may not give warning signs before they release; they are most commonly triggered from terrain features with shallow or variable snowpacks, or if avalanches in the upper snowpack gain enough mass to step down.  

    A human-triggered persistent slab avalanche that failed on buried surface hoar and stepped down into older weak layers as well.

     

Avalanche Discussion

I'm at a loss for words this morning after a devastating weekend involving a serious injury on Snodgrass and a fatal avalanche in the Anthracites.  A pursuit that brings so much joy to our community can so abruptly take that joy away, and we lost someone who truly embodied that sense of joy yesterday.  Take care of yourselves and each other, CB State of Mind offers local mental wellness services for trauma and grief.  

Field observations suggest that the February persistent slabs are becoming more stubborn in the deeper Northwest Mountains.  Evan's video from Schuylkill Ridge on Saturday describes the situation: decreasing sensitivity while slabs remain 2 to 3 feet thick.  Slabs are still soft and shallow enough that human triggering remains a very serious threat. Variability from slope to slope is now common due to both slab variability and differences in how large or preserved the surface hoar or near surface facets were at the start of our loading period on February 2nd.  For example, these pre-storm obs from the Beckwiths, Peeler Peak, and Axtell describe how our problematic surface hoar changed across the landscape.   On the most troublesome aspects highlighted above, assessing or predicting that variability is a challenge fraught with uncertainty; lower slope angles and less consequential terrain features are the most reliable tools right now as we give the snowpack its due time to adjust.

Observations suggest persistent slabs remain reactive in the shallower Southeast Mountains.  Skiers on Teocalli yesterday reported widespread collapses and remotely/sympathetically triggered an avalanche from a half mile away.  At lower elevations, the latest generation of slabs are thinner and aren't as widespread on a zone-wide scale. Still, expect to encounter some instabilities on steeper terrain features, especially closer to the zone boundaries and as you get closer to treeline.  Sunday's triggered avalanche on Snodgrass and this recent slide on Meridian Lake are examples.  There is also a greater threat of triggering an avalanche that breaks into early-season weak layers in the Southeast Mountains.  

Northerly winds over the past 24 hours were just strong enough to form a few fresh drifts on leeward terrain features in the alpine. It's a relatively minor issue compared to our persistent slab problem, but something to stay alert for in consequential terrain above treeline.

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