Bollettino valanghe

Northwest Mountains

Crested Butte Avalanche Center
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Pericolo valanghe

Mon
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

We are experiencing abnormal mid-winter conditions as if it were mid-December and not late March. Wide propagating and remotely triggered persistent slab avalanches are occurring. In some cases, these avalanches are very large and unsurvivable. The most dangerous areas are previously wind-loaded terrain at near and above treeline elevations. Save those more aggressive spring lines for whenever spring arrives and consider enjoying the good snow with more conservative terrain choices. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    Since Monday (3/20), 2 to 3 feet of snow has accumulated on a new round of persistent weak layers. The greatest number of avalanches have occurred on easterly-facing slopes where a collapsible crust exists. Similar conditions can be found on westerly-facing slopes. While on northerly facing slopes these slabs are resting on a layer of near-surface facets. Avalanches on these weak layers are exhibiting persistent slab characteristics with wide propagation and remote triggering. Some avalanches have further stepped down to even deeper weak layers and produced destructive avalanches. Recent wind loading is keeping this avalanche problem more sensitive to triggering at near and above treeline elevations. 

    Early warning signs for this avalanche problem are rare. So don't expect much for direct feedback. The majority of avalanches are occurring on steep slope angles near and above 40 degrees. You can reduce your chance of triggering this avalanche problem by avoiding wind-loaded terrain and limiting slope angles to 35 degrees or less, without steeper slopes above. 

    3:23 A pile of natural avalanches ran on Purple Ridge (easterly aspects).  The sharpness of the crowns suggests failure occurred at the tail end of the storm during the second half of Wednesday.  Nearly all of the avalanches pictured here are big enough to bury and kill you.

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    Westerly winds on Friday night and into Saturday have built fresh wind slabs and further loaded the deeper persistent weak layers at near and above treeline elevations. A triggered slab avalanche could release 1 to 2 feet deep, or step down into more deeply buried weak layers. Complicated avalanche conditions exist in these locations. You can avoid the wind slab avalanche problem by sticking to sheltered terrain and/or avoiding the lee sides of ridgelines and cross-loaded terrain features. 

    A human-triggered avalanche on 3/18, that propagated into a wind-loaded terrain feature, with a triple overhead crown and an unsurvivable avalanche. 

Avalanche Discussion

Remotely triggered persistent slab avalanches have been the main headlines in recent observations. On Friday, an avalanche was remotely triggered from a few hundred feet away on a west-facing slope below treeline, and another avalanche was remotely triggered on a south-east facing slope below treeline. On Saturday another couple of avalanches were remotely triggered on east-facing slopes below treeline, and 3 very large avalanches were remotely triggered on southeast-facing slopes near treeline. Those 3 very large avalanches should grab your attention, as avalanches of that size are difficult to survive. The observation tab is further populated with documentation of the recent natural avalanche cycle that occurred last week and a few more very large natural avalanches such as this one in Barcelona Bowl, and this one on Cement Mountain. 

The recent storm from Monday, 3/20 through Wednesday, 3/22 deposited a slab that is 1 to 3 feet thick in sheltered terrain and much deeper on drifted slopes. That snow has buried a new round of persistent weak layers and has further added stress to more deeply buried weak layers. 

Since the middle of March, we have been in a steeping back mindset as avalanche conditions have become complicated, and more unsurvivable avalanches are being documented. We are now entrenched in these conditions. Even though it is late March, this isn't a great time for big spring lines and aggressive terrain choices. The current avalanche problems will eventually settle out and they just need to be given some time to do so. 

Regioni coperte