Bollettino valanghe

Gunnison

Crested Butte Avalanche Center
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Pericolo valanghe

Tue
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

A strong and prolonged storm will significantly change avalanche conditions this week.  The avalanche danger will start rising from MODERATE today towards CONSIDERABLE overnight.  During the daylight hours, monitor new snow accumulations and watch for fresh slab development where the wind is transporting snow.  Sluffing will continue to be a threat on steep, northerly aspects where the snow surface is loose and sugary.   Expect natural activity to develop overnight on northerly aspects as snowfall and wind loading intensify.

Problemi valanghivi

  • Wind Slabs

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

    Southwest winds will increase today and new snow will add additional fuel for transport.  Watch for thin but sensitive drifts to form at higher elevations, especially once snow starts falling later today.  Look for blowing snow to alert you to the hazard.  You're most likely to find fresh slabs forming on the leeward side of ridges or in crossloaded gullies.  Cracking in the snow is a warning sign.  Drifted slabs near treeline could entrain more snow than expected if they run through weak, faceted snow lower in the track or step down into a lingering old hard slab.

    2/18. Purple Ridge, NE, 11,000t NTL. Heavly crossloaded terrain feature. Best guess is that the crown averaged in the 6 to 12″ range, and maybe a bit deeper where it broke into the wind wale. D2 in size.

  • Loose Dry

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

    Dry loose avalanches (sluffs) are a concern in wind-sheltered terrain on the north half of the compass.  Where the snow surface is weak and cohesionless, you can easily trigger sluffs that entrain the top 6" to 12" of loose snow on slopes steeper than 35 degrees.   Ski cuts, moving across the fall-line while descending, or choosing lower-angled slopes are effective techniques to manage this problem. These point-release avalanches will accumulate more mass in long-running, steep terrain. Use caution above gullies where an avalanche can pile more deeply and above trees and cliffs where the consequences of getting caught in a sluff will be magnified. This problem is most common in sheltered terrain below treeline, but you can also trigger sluffs on some near treeline slopes and a few above treeline slopes.    

Avalanche Discussion

The danger has been gradually trending down over the past couple of days, but starting this afternoon, the trend takes an abrupt and dramatic reversal.  Snowfall and wind loading will start up this afternoon and intensify overnight. Expect dangerous avalanche conditions to develop tonight. This is the first real storm to test our exceptionally weak snow surfaces (See this video).  For today, newly developing slabs will be confined to wind drifted terrain, while sluffs entraining all of the weak faceted snow will remain a manageable concern in sheltered, northerly terrain.  Tonight, instabilities will become larger, more widespread, and natural activity will be underway.  

Observations from the weekend suggest that the persistent hard slab problem that developed from the early February wind events has become stubborn enough that we are phasing it off the list for now.  Additional loading this week will re-ignite the issue, but more importantly, we'll see slab development that is much more widespread and sensitive, which will dictate our travel advice throughout the week. 

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