Bollettino valanghe

Southeast Mountains

Crested Butte Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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In sintesi

Recently wind-loaded terrain at near and above treeline elevations is the most concerning area for triggering a dangerous avalanche. A triggered avalanche in these locations could release in the upper snowpack, or step down deeply into older snow layers. In wind-sheltered areas on the northern half of the compass, you can reduce your chance of triggering a persistent slab avalanche by riding less complex terrain with slope angles in the lower 30-degree range. Riding conditions have also been great on wind-sheltered south-facing slopes, and those sunny slopes also have the lowest concerns for triggering a slab avalanche. 

Problemi valanghivi

  • Wind Slabs

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

    Yesterday afternoon, 12,000ft wind stations recorded westerly winds in the 20mph range with stronger gusts. Today, the wind direction will be northwest to north, with an increase in wind speeds occurring around mid-day or this afternoon. Human triggering a wind slab will become likely by this afternoon in areas that are receiving active wind-loading. In these same areas, natural avalanche activity will become possible. The travel advice is avoidance of freshly wind-loaded terrain features, especially where the wind slab avalanche problem overlaps the persistent slab avalanche problem. 

    Example of active wind-loading from earlier this winter. 

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2.5

    On the northern half of the compass, you can trigger a dangerous slab avalanche that breaks up to several feet thick on weak faceted snow that was buried last month. Slabs can be triggered remotely from below or adjacent slopes. Collapsing and cracking are clear signs of instability, although direct feedback on this problem has become less frequent. The most concerning areas are where the wind has continued adding load and slowly building slabs. You can decrease your chance of triggering this avalanche problem by avoiding those wind-loaded areas, and choosing slopes had have slope angles in the lower 30-degree range.

    This persistent slab caught and partially buried a snowboarder last weekend on a northeast aspect below treeline. The snowboarder triggered the avalanche from below the slope while he was hiking uphill.  

Avalanche Discussion

Fairly continues accumulating snow this week has created some excellent riding conditions around the compass. Total snow accumulations have stacked into the 1 to 2-foot range for the SE Mountains and 2 to 3+ feet in the NW Mountains. This has been one of the few times this winter where we have seen snow stack up, without a notable natural avalanche cycle. A prolonged dry spell earlier this winter left behind an exceptionally weak snowpack. We dubbed that weak layer of snow "the sandbox layer".  In early March, the sandbox was cooked into thick crusts on southerly facing slopes but remained on northerly facing slopes.  If we had seen this week's snow stack up in a shorter 24 to 48-hour timeframe, we certainly would have seen a natural avalanche cycle on the northern half of the compass. However, the slow but steady load had not produced an avalanche cycle. Instead, those slabs have been allowed to grow in size, and increase the consequence if a human finds the right trigger point to upset that balance. 

The most consistent loading this week has been at near and above treeline elevations. In these areas, there are copious amounts of snow available for transport, and we've seen periods of increased winds continue to load that snow onto the lee sides of terrain features. With another round of increased winds forecasted today, the avalanche danger will remain at CONSIDERABLE. Just how much loading occurs this afternoon, will be the driver for tomorrow's avalanche danger rating. If there is less loading than currently expected, we could see a drop to MODERATE avalanche danger as early as tomorrow. 

At below treeline elevations, the avalanche danger has dropped to MODERATE for the NW Mountains and remains CONSIDERABLE in the SE Mountains for another day. In short, where the February Sandbox is buried deeply, like in the NW Mountains, it has gained some strength and become stubborn to human triggering. However, where that weak layer has been closer to the snow surface, conditions have not been so favorable and it has remained more notably weak. Having a weak layer closer to the snow surface is also easier for the weight of a human to affect. The SE Mountains were given one more day before the below treeline avalanche danger is dropped to MODERATE. Kinler has summarized these conditions well in his recent observations here and here. 

Regioni coperte