Bollettino valanghe

Southeast Mountains

Crested Butte Avalanche Center
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Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Dangerous avalanches are easy to trigger on or adjacent to some steep terrain.  On west, north, and east aspects,  avalanches can be remotely triggered from flat terrain, and slabs can entrain most of the snowpack once they get moving in more sheltered areas.  You can safely enjoy the powder on slope angles consistently less than 30 degrees that don't connect to steeper terrain above you.  This terrain map can help you choose simpler terrain.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2.5

    Soft slabs of new and drifted snow averaging 2 feet thick will be most sensitive to triggers where they formed over fragile facets, collapsible crusts, or surface hoar layers on west, north, and east aspects.  Slab behavior is becoming more challenging as slabs stiffen and thicken, with increasing potential for remote triggers and wider propagation around terrain features.  On these same aspects at mid and low elevations, avalanches will grow larger as they entrain the weak, sugary snowpack under the new snow.  Cracking and collapsing are blatant warning signs to travel on slope angles less than 30 degrees, though not all slopes will give obvious feedback.  

    Older, hard slabs exist below the storm snow on some leeward slopes and can produce avalanches that are more surprising or difficult to manage. Identifying the locations of these older slabs is now challenging beneath the new snow.  

    A pair of remotely triggered avalanches on Snodgrass.  12/29.   

  • Storm Slabs

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

    While most avalanches are expected to break on persistent weak layers described above, instabilities within the storm snow or breaking on top of crusts lacking persistent weak layers are also a concern around the compass.  Last night's snow was top heavy, which could cause shallow storm instabilities that step down once they get moving. On southerly aspects, monitor how the recent snow is bonding to slick crusts and stay alert for solar-triggered sluffs before riding in steeper terrain.  Small, steep test slopes can be used to gather feedback before riding in bigger terrain.  Shooting cracks are signs to choose mellower terrain.  

    An example of a storm slab from the archives.

Avalanche Discussion

Observers yesterday reported easily triggered slab avalanches breaking about a foot deep in the Southeast Mountains (ex. Snodgrass) and two feet deep in the Northwest Mountains (ex. Washington Gulch, Irwin) on the problematic aspects highlighted by the persistent slab rose.  This observation from near Marble yesterday also highlights the very sensitive conditions and large natural activity adjacent to our deep zone.  Most of the human-triggered avalanches yesterday were remotely triggered, meaning you can trigger and be buried by an avalanche by traveling underneath a steep slope.  The combination of warmer temperatures and additional loading overnight stiffened slabs. This will cause slabs to fail wider or be triggered from further distances today, while sensitivity may decrease a small amount in some deeper areas.  This is certainly a setup to avoid in steep terrain unless you're traveling on slopes that already flushed.

We likely saw another period of natural avalanche activity overnight with an additional .3" to .7" of SWE and rapidly consolidating slabs under warming temperatures.  We should see a downturn in natural activity under relatively light winds and dry weather today.  Large naturals are possible from warming-related releases, especially if solar-triggered sluffs run over the aspects highlighted by persistent slabs.  Winds are expected to increase significantly tonight and tomorrow, which will cause more loading onto our snowpack and likely increase the danger on windloaded slopes.  Our forecast team has the most uncertainty for above treeline slopes, where snow surfaces before the storm were most commonly stout wind crusts over facets.  That setup has a higher threshold for withstanding loading but potential for wider and more destructive avalanches when it fails.  

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