Bollettino valanghe

Northwest Mountains

Crested Butte Avalanche Center
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Pericolo valanghe

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

In sintesi

Human-triggered avalanches remain a concern on upper-elevation slopes facing northerly or easterly directions.  You can confidently predict the presence of a poor snowpack structure in these places and the potential to trigger a large avalanche.  There could be isolated northerly slopes below treeline between 10,500 and 11,000 feet deep enough to create a slab avalanche.  You can generally find a safer snowpack below treeline and southerly-facing terrain.

Problemi valanghivi

  • Persistent Slabs

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

    You will find a fragile base to the snowpack on northerly and easterly aspects from the early seasonal snowfall that accumulated back in October.  Storms during the second half of November deposited up to 2 feet of snow on top of these Persistent Weak Layers.  Observations from last weekend included natural avalanches, collapses, shooting cracks, and remotely-triggered avalanches.   Several days of stable weather brought slight improvement to the Persistent Slab problem.  The threat of large human-triggered avalanches remains for upper elevation slopes but conditions have eased below treeline.  Cold temperatures have weakened slabs below treeline leaving most slopes without much hazard,  However, there could be an isolated slope at the highest portions of the below treeline elevation band where a slab avalanche is possible.  This observation from Purple Palace illustrates one of these isolated below treeline slopes.

    This persistent slab avalanche was remotely triggered from below on Purple Ridge. 11/26

Avalanche Discussion

Since last weekend the avalanche hazard slowly improved under stable weather conditions.  Most slopes below treeline don't pose much threat for slab avalanches.  Recent cold weather has weakened the slabs that formed during the second half of November and left a soft, weak snowpack throughout.  However, there could be an isolated slope or terrain feature with just enough strength for a slab avalanche.  One of these isolated slopes is more likely to be found in the Northwest Mountains and not in the Southeast Mountains.  Look for signs of instability like collapsing or cracking to help alert you to one of these isolated slopes.

Upper elevation slopes highlighted by the Persistent Slab problem continue to present worrisome structures with a clear strong over weak snowpack.  Selecting conservative terrain is the best way to manage the problem if you travel on suspect aspects at upper elevations.  A safer choice would be to travel on sunny aspects at upper elevations where you are unlikely to encounter the problem.

Looking forward, a prolonged stormy period is forecasted to begin Thursday night and last through early next week.  Expect avalanche hazards to worsen in the coming day with a good chance that we experience dangerous conditions.  Weak snow is common across the mountains and you should anticipate that the safe slopes of today could become dangerous this weekend.  Follow the forecast each day to stay ahead of the changing conditions.

Regioni coperte