Boletín de aludes

Northwest Mountains

Crested Butte Avalanche Center
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Peligro de aludes

Wed
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 4 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Strong winds and up to 8" on Sunday night formed small wind slabs scattered across higher elevation terrain, easily triggered by skiers yesterday.   Be cautious of lens-shaped, thicker-looking drifts if you are riding in high-consequence terrain above cliffs, gullies, or trees. 

Problemas de aludes

  • Wind Slabs

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

    Up to 8 inches of snow and gusty winds in the past 36 hours formed small drifts in wind-affected terrain.  Sunday night's winds were strong out of the southwest, and have since shifted to the north at lighter speeds. To identify the problem, look for signs of recent drifting, such as thicker or denser wind deposits and cracking underfoot.  Today's wind slabs are generally small and will be most harmful if they push you into a terrain trap.  They'll be most common near ridgelines and concave terrain features or rollovers that catch drifting snow.  

    2/6:  A skier triggered wind slab on a leeward slope on Mt. Emmons. 

Avalanche Discussion

Today's avalanche danger is driven by the threat of small wind slabs across the entire forecast area at higher elevations, and low likelihood/high consequence persistent slab concerns in shallower parts of the Southeast Mountains.  The Sunday night through Monday morning storm brought 8" at Irwin and 3" at CBMR, with initially strong winds out of the southwest.  Skiers yesterday triggered small slabs in wind-affected terrain. It's worth highlighting that one of these was unintentionally triggered further down the slope than expected.  The wind slabs formed over a faceted snow surface, so they will probably remain sensitive to triggers today.  I expanded the distribution rose of wind slabs in the alpine after last night's gusts out of the northwest to the northeast may have formed fresh drifts on the opposite side of the compass.  This problem is generally small, but something you'll want to manage in high-consequence, wind-affected terrain.  

We're shifting the upper snowpack persistent slab (our mid-January near surface facet layer) from stubborn to unreactive in our assessments.  Dozens of aggressive tracks in suspect terrain over the weekend and recent targeted stability tests (Ex A, Ex B) provide evidence of the upper snowpack persistent slab problem becoming increasingly rare, so we've removed it from our problem list.  In contrast, persistent slabs breaking on basal weak layers are still a concern in the Southeast Mountains because those depth hoar layers are much larger and better developed, thus slower to improve.  Evidence of the lingering problem comes from a close call last Wednesday, just outside of our forecast area on Park Cone, and unstable pit results over the weekend on a shallow, windward slope near treeline by Gothic.  

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