Bollettino valanghe

Northwest Mountains

Crested Butte Avalanche Center
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Pericolo valanghe

Fri
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto last year. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

An Avalanche Watch is in effect.  The avalanche danger will rise through the day due to heavy snowfall rates and strong winds.  Large avalanches will become easy to trigger and can run naturally on wind-loaded slopes by later today. There's increasing potential for wind slab avalanches to step down and trigger a deep slab at higher elevations. The danger could rise to High at upper elevations tonight.  In sheltered terrain, storm instabilities will become more dangerous by this evening.  

Problemi valanghivi

  • Wind Slabs

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

    Strong southwest winds are drifting the new snow into sensitive wind slabs below leeward ridges and in crossloaded terrain.  Slabs will grow in size through the day, and in some cases, overlap with an older and more stubborn generation of wind slabs that formed earlier this week.  Avoid traveling on or below leeward slopes for a safer day.  Blowing snow, thick feeling drifts, or cracking are obvious signs of danger.  There is potential for a wind slab to step down and trigger a much larger avalanche that breaks on deeper weak layers.  

    A skier triggered wind slab on Purple Ridge  (3/4/2025) 

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2.5–3.5

    Deeply buried facets and depth hoar layers on the northern half of the compass are becoming more concerning with this loading event.  Slabs on top of these weak layers are several feet thick or more and capable of producing destructive avalanches.  The problem is stubborn to triggers: the most concerning terrain for triggering a deep slab is near and above treeline in rocky or wind-drifted terrain where slabs thin.  Avalanches can break widely across multiple terrain features and be remotely triggered from flat terrain near or below steep slopes without warning signs.   Windloading, cornice falls, or avalanches in the upper snowpack could be natural triggers.   The problem can generally be avoided on slope angles consistently less than 30 degrees or on southerly aspects.  

    An example of a very large deep slab avalanche that broke on depth hoar layers near the ground in the Elk Mountains last week.  

  • Storm Slabs

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

    In wind-sheltered terrain, slab avalanches can break in the new and recent snow.  Storm slabs are expected to be relatively small and possible through most of the daylight hours, and become more widespread and grow larger near or after sunset due to heavy snowfall.  Cracking on steep test slopes can help you identify the problem.  Monitor new snow amounts and choose mellower and less consequential terrain as slabs grow in size later today or tonight.  

    Cracking in the storm snow is a sign of unstable storm slabs.  These cracks were triggered yesterday - about a foot deep.  

Avalanche Discussion

Conditions will change dramatically in the next 24 hours; bring a stepping-back mindset to the backcountry today. Yesterday, skiers triggered a few small storm slabs in favored areas near Kebler Pass. We won't see significant changes below treeline until we see more than a few hours of heavy snowfall rates, which appear to hold off until late afternoon or evening per model guidance.   The danger will flip from Moderate to Considerable below treeline once we get about a foot of new snow. 

Winds are already ramping up the danger at higher elevations this morning. They will continue to increase the danger throughout the day as more snowfall adds fuel to increasing wind speeds later this afternoon and tonight.   Wind loading is now pointed directly at our most worrisome aspects for persistent and deep persistent slabs, forming wind slabs and stressing cornices above the slopes that can produce D3 avalanches if they fail near the ground.  Persistent slabs could become likely in shallower parts of our forecast area tonight.  Consider your overhead hazards today and stay off those slopes catching heavy windloading.  With strong to extreme winds over the next 24 hours, wind slabs may form in unusual locations.   

The peak of instability and natural activity looks to happen tonight, and High danger may pass during the overnight hours while most of us are comfy and cozy at home.  Tomorrow's danger will hinge on how the storm plays out and if we are still in an active snow/windloading pattern at sunrise.  

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