Bollettino valanghe

Northwest Mountains

Crested Butte Avalanche Center
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Pericolo valanghe

Thu
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 9 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Signs of instability have continued to emerge since Sunday's storm and small natural avalanche cycle.  The most likely place for you to trigger an avalanche is on the north half of the compass near and above treeline or upper elevation terrain with previous drifting.  If you ride northerly-facing terrain, you can reduce your risk of an avalanche by choosing slopes less than 30 degrees.  Wind-sheltered, southerly terrain often lacks the problematic weak layer, providing lower-risk terrain options. 

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–1.5

    It may be easy to trigger soft slabs about 10 to 16 inches thick (thicker on wind-loaded features) on the north half of the compass, where the new snow accumulated on fragile facets.  The problem could be found below the treeline, but less commonly than at upper elevations.  Beware of remote triggering potential on steep slopes above you.  Shooting cracks and recent avalanche activity are clear signs of instability: manage the problem by choosing smaller, less consequential terrain or lower slope angles.   You can reliably avoid the problem by traveling where the new snow fell on bare ground on southerly aspects.  Some high elevation, southerly aspects held old crusts before the storm: evaluate how well the new snow is bonding to these crusts before committing to steep terrain.  

    (12/1/2025)

    An example of a natural avalanche observed on Monday (northeast-facing above treeline).  You can trigger a similar avalanche on wind-drifted slopes facing the north half of the compass today.

    Photo: Crested Butte Avalanche Center

  • Persistent Slabs

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

    Below Sunday's snow,  dense old slabs one to two feet linger on previously drifted, high-elevation northerly slopes.  An avalanche in the storm snow could step down and create a larger-than-expected avalanche.  Beware of previously cross-drifted terrain in high northerly areas that attract early-season riders; these features might have the problematic ingredients of a harder slab over old faceted October snow.  Large collapses, like this observation from Cinnamon, are clear signs you’ve found this problem.

    A remotely triggered slab on the north side of Mt. Baldy on Nov 22.  This slope held an old layer of weak snow from October's snowfall, buried beneath 1 to 2 feet of drifted snow.  

Avalanche Discussion

A layer of weak snow is fairly continuous on the north side of the compass from snowfall in October and mid-November.  A storm this Sunday, November 30th, deposited 8 to 16 inches of snow across this weak layer, accompanied by northwesterly winds strong enough to redistribute the snow at upper elevations.   A small natural cycle was documented on Monday, and signs of instability have been noted each day since (Anthracites, Mount Baldy, Baxter Basin).  More snow accumulated in the Northwest Mountains and at upper elevations, so the most likely place to trigger an avalanche is in these areas.  Lower elevations below roughly 10,000 feet and the Southeast Mountains received less snowfall, reducing the threat of avalanches.  In these areas, previous wind loading is often a necessary ingredient to form a small slab.  Most avalanches are expected to remain small in size, but given the shallow snowpack, any ride in an avalanche could be hazardous.  An outlier large-sized avalanche couldn't be ruled out on the most drifted slopes, or if you happened to find an isolated spot identified in the Persistent Slab problem.  One of these slides may be bigger than you expect.

Some uncertainty exists with the impact of today's weather.  Up to 6 inches of snow may accumulate, gently increasing the hazard.  Thankfully, wind speeds appear to be light with little to no drifting expected.  However, Sunday's avalanche cycle was small, with most natural avalanches coming from high elevations or wind-drifted features.  The additional snow could increase the sensitivity or increase the distribution below treeline.  Carefully monitor snowfall rates, and if you encounter 6 inches or more of new snow, then the hazard is increasing.

 

Upcoming Events: 

  • Holiday Tree Sale: December 3rd-5th from 3 pm-7 pm at Ace Hardware
  • Avalanche Awareness Night: Saturday, December 6th at the Center for the Arts. Doors at 5, show at 6:30.
  • Beacon Brush-Up: Sunday, December 7th, 9 am - 2 pm at the Community School

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