Bollettino valanghe

Southeast Mountains

Crested Butte Avalanche Center
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Pericolo valanghe

Mon
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
4 · Forte
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In sintesi

An Avalanche Warning is in effect.  Heavy snowfall and strong winds are creating easily human-triggered and natural avalanches, some of which could be very large and run long distances.  Traveling on or below slopes steeper than 30 degrees is not recommended.  The largest and most dangerous avalanches will be breaking on wind-loaded slopes at higher elevations or on the north half of the compass below treeline.  This avalanche terrain map can help you make a plan to avoid avalanche terrain.   

Problemi valanghivi

  • Persistent Slabs

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

    In the Southeast Mountains, we're expecting many avalanches to fail on buried weak layers today, producing large to very large avalanches.  The most prominent and active weak layer is buried surface hoar a couple of feet deep on the north half of the compass. There is also smaller potential for avalanches to break on faceted crust layers on some higher, southerly aspects, or depth hoar layers near the ground.  Persistent slab avalanches can be remotely triggered from low-angle terrain and break larger and wider than you might expect.  Avalanches breaking into old weak layers are unlikely on low elevation, southerly aspects.  Slope angles consistently less than 30 degrees away from runout zones are a reliable way to avoid the problem.

  • Storm Slabs

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

    Up to a foot of snowfall and strong winds will form easily triggered slab avalanches in the new snow.   Slabs will be largest and most sensitive in wind drifted terrain near and above treeline.  A triggered or natural storm slab could step down and trigger a much larger persistent slab avalanche.  At lower elevations where the problem doesn't overlap with persistent slabs, carefully assess slab size, bonding, and terrain consequences before riding on slopes steeper than 30 degrees.  

Avalanche Discussion

The storm is performing as expected, along the lower end of our expected range of outcomes.  By the end of the day, we're expecting about 10" to 20" across our forecast area, with strong winds westerly winds intensifying loading at higher elevations.   By themselves, storm slabs thickened by wind drifting are dangerous enough to warrant avoidance of leeward avalanche terrain and cautious route-finding elsewhere.   However, conditions are more complex and more dangerous because of our troublesome buried weak layers.  

As far as our persistent slab problem is concerned, this looks to be the biggest hit on our snowpack since our February weak layers were buried.  Imagine your scrawny friend who has struggled to hold the barbell all month, and you just added a pair of big weight plates overnight.  That's a good illustration of our snowpack, especially the Southeast Mountains which have shown a significant pattern of continued persistent slab activity in recent weeks.   Although we may not see as much persistent avalanche activity in the Northwest Mountains, any avalanches that break on old layers are likely to run long and far, potentially reaching the valley floor, similar to the Axtell slides last week.  The most intense loading right now is happening on windloaded slopes; near and above treeline terrain is very dangerous.  We have less confidence about whether this storm is enough to break the camel's back below treeline.  Even though storm totals are smaller in the Southeast Mountains today, there's a higher potential for the surface hoar to wake up in a big way below treeline, along with greater concern for many dangerously large avalanches starting high and running far into below treeline terrain in our shallower zone.  Thus we're showing High Danger at all elevations below treeline in the Southeast Mountains.    

Events: The CBAC Fireside Chat Series presents legendary American alpine climber George Lowe on Sunday, March 3 at the Mallardi Cabaret Theatre in downtown Crested Butte at 6 p.m. Best of all, it’s free!

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