Boletín de aludes

Northwest Mountains

Crested Butte Avalanche Center
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Peligro de aludes

Fri
Alta montaña
4 · Fuerte
Límite del bosque
4 · Fuerte
Bajo el límite
3 · Notable
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Desactualizado: este boletín caducó 4 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

An Avalanche Warning is in place.  Another pulse of snowfall accompanied by drifting snow from westerly winds will overload the snowpack.  An increase in westerly wind speeds is likely to spur another round of natural avalanches on drifted terrain.  Select low-angle terrain that is not below steeper slopes where you find old snow near the ground.  Travel in avalanche terrain is not recommended today.   

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Very Likely
    Tamaño
    2–3

    Days of snowfall and increased westerly winds on Thursday have the snowpack teetering on the edge of failure.  There's a widespread weak layer of facets and faceted crusts buried by 2 to 4-foot slabs on west to north to southeast aspects. The slabs are largest in leeward terrain at higher elevations.  The problem is less common, but still possible, on windward terrain or south-facing slopes that hold old snow layers near the ground.  Choose routes that keep you off and out from under steep terrain that holds old snow below our recent storms.  Collapses and shooting cracks are clear signs of danger warning you to stay on slope angles that are consistently less than 30 degrees.  Avalanches on drifted terrain could reach to very large sizes in the Northwest Mountains.

  • Storm Slabs

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

    Up to 24 inches of snow fell in the past 36 hours, with moderate winds last night.  You are most likely to trigger a storm slab avalanche at higher elevations where winds have stiffened the recent snow. At lower elevations, loose dry avalanches are more common.  Cracking in the upper snowpack is a clear sign you have found sensitive conditions in the recent storm snow.  Relatively shallow releases in the storm snow are likely to step down and trigger a larger persistent slab avalanche where the two problems overlap. 

Avalanche Discussion

Overnight snow totals range from 3 to 7 inches with up to .4 inches of water as of 5 am.  A couple more inches are expected in the few hours after sunrise.  Winds from the west are blowing in the 20s and gusting to 50 at upper elevations.  The increase in wind speeds will allow substantial amounts of this week's snowfall to be transported to leeward terrain features.  These factors point to dangerous natural avalanche activity at upper elevations and easily human-triggered avalanches in sheltered terrain.  Yesterday, observers documented dangerously large natural avalanches on Axtel, Gothic, and Mount Owen, and human-triggered avalanches in sheltered terrain on Snodgrass.  Expect similar very dangerous avalanche behavior today.

Any terrain that you encounter, or expect to find, old snow near the ground should prompt you to select low-angled slopes free from overhead hazards.  Slabs have gained strength, but weak layers have not.  This means you can trigger avalanches from a great distance even from below.  Most natural and human-triggered avalanche activity will be large enough to bury and kill you.  Avoiding avalanche terrain will be your best defense against a dangerous encounter with moving snow.  Travel in avalanche terrain is not recommended.

The snowpack isn't nearly as dangerous on slopes that were bare dirt prior to our recent storms.  These two observations from the Northwest Mountains and Southeast Mountains document the distribution of our problematic weak layer that formed during November's dry spell.  In terrain that's lacking the troublesome old snow layer, you'll need to manage storm instabilities that developed over the past few days of snowfall and wind.  Even steep terrain without old snow near the ground requires conservative decision-making and terrain selection as an avalanche just in recent storm snow can be large enough to bury and kill you.

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