Boletín de aludes

Gunnison

Crested Butte Avalanche Center
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Peligro de aludes

Mon
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 2 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Steer away from old, hard drifted slabs or fresh new drifts to reduce the chances of triggering a rare slab avalanche.  In wind-protected terrain where the snow surface is soft and sugary, stay alert for gouging dry, loose avalanches on very steep slopes, especially in consequential terrain.  

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely
    Tamaño
    1–2

    Slabs up to several feet thick are becoming increasingly isolated and difficult to trigger but remain a concern on a few previously wind-drifted slopes.  You are unlikely to see signs of instability before triggering an avalanche that breaks on old weak layers.  The most concerning terrain features are where old, drifted slabs are thin near their margins, convexities, or rocky areas. You can reliably avoid the problem on slope angles less than 30 degrees without steeper slopes above you, and wind-protected terrain generally lacks the problem.  

    This avalanche was triggered by a backcountry rider on 1/26 outside our forecast area near Ashcroft. This is a good illustration of the wind forming a slab below a midslope roll. 

    Photo courtesy CAIC. 

  • Loose Dry

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–1.5

    You can easily trigger gouging  "facet sluffs" on a few of the most wind-sheltered slopes where slope angles are steeper than about 40 degrees.  You're most likely to encounter the problem in start zones that have avalanched multiple times this season and have an unusually shallow and weak snowpack (<50 cm).  These avalanches release predictably and start small, but can grow to harmful sizes in long relief or if they push you into trees or gullies.  Use defensive or off-fall-line riding techniques to manage the problem, or move to lower slope angles to avoid the problem.  

    A debris pile from dry loose avalanches accumulating in a gully below the Climax Chutes. 

Avalanche Discussion

Sticking with the groundhog theme, our snowpack and travel advice feel like they have been on a daily loop because changes to our snowpack have been subtle and very gradual.  One of these subtle changes was a prolonged period of increased east-to-north winds that ended on Friday.  We're finding that those unusual winds worked through more of our wind-sheltered terrain. This damaged the snow quality while reducing the number of slopes capable of producing facet sluffs.  Of course, everyone is hunting for those soft, wind-protected turns. If you search hard enough, you will still find a steep, sheltered slope - the same type of terrain where it is easy to trigger a gouging sluff that can push you into trees or a gulley if you let your guard down. 

Alternating wind directions over the past few weeks with limited snow available for transport have eroded numerous slopes while depositing harder slabs in favored features such as concavities in the terrain or behind ribs or ridges at all elevations.  Those slabs are generally stubborn to trigger, though stability tests suggest you can still trigger one if you hit the sweet spot somewhere on the wrong slope.  Eric's observation from Cement Creek illustrates the types of slopes (smooth, rounded, drifted) where you might still find trouble. Our most recent winds have shifted to the southwest, with up to 2" of new snow to drift into leeward features. That's not much, but enough to form a few thin but sensitive wind slabs in favored terrain.  If you're riding in terrain where you can't afford to get pushed off your feet by a small slab, monitor for fresh drifts.  

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