Bollettino valanghe

Gunnison

Crested Butte Avalanche Center
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Pericolo valanghe

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

In sintesi

Cautious route-finding and conservative decision-making are still warranted as the current warmup adds uncertainty to how the snowpack will tolerate this change. If a slab avalanche releases naturally or from a human trigger, it will likely be large and destructive. You can reduce your chance of triggering one of these slabs by choosing terrain with lower slope angles and a deep/uniform snowpack. Persistent slabs are more likely to be human-triggered from areas with variable snow depths and/or many trigger points. As the sun warms the snow surface, wet loose avalanche activity will also increase on the southern half of the compass. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3.5

    Weak facets and collapsible crusts are widespread on the northern half of the compass and on some sunnier aspects at high elevations.  Slabs on top of these weak layers average 2 to 3 feet thick in wind-sheltered terrain. Slabs are thicker and harder in wind drifted terrain and can step down through older slabs to the ground.    This problem is becoming more stubborn to triggers, often requiring a thin spot on the slope, such as near buried rocks, trees, or where slabs thin from wind effects. Avalanches can break widely across multiple terrain features and be remotely triggered from flat terrain near or below steep slopes without warning signs. The problem is less common on south and southwest aspects, and can be avoided on slope angles consistently less than about 30 degrees.  

    These destructive persistent slabs released on Wednesday 2/19. 

  • Loose Wet

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

    As temperatures rise and the sun warms the snow surface, the potential for wet loose avalanche activity will increase. Pinwheels and roller balls are an early warning sign that this avalanche problem is developing, and a loose wet avalanche may release on a steep slope. Consider avoiding travel on or under steep sunny slopes as you see this avalanche problem developing, or if you find a few inches of wet snow on the snowpack surface. 

    An example of roller balls and small loose wet avalanches from Saturday. Most commonly releasing from hot spots on the slope, such as rock outcrops in this example. 

Avalanche Discussion

High temperatures today climb a couple of degrees warmer than Saturday, and again, climb a couple more degrees on Monday. This warming temperature trend is adding uncertainty as to whether the persistent slab avalanche problem will continue to become less reactive or if there will be a period of more reactive conditions during the warmup. Given the destructive size and potentially deadly outcome of getting caught in one of these avalanches, dangerous avalanche conditions and CONSIDERABLE avalanche danger prevail through this warmup. As we get to the other side of the warmup, the volume of snow available for entrainment will have notably decreased and allowed the potential size of an avalanche to come down a notch, and some aspects may be removed from the problem rose as new crusts have formed. This combination will finally allow the avalanche danger rating to decrease. 

Wet loose avalanche activity increased yesterday but remained small in size. Given the gradual nature of this recent warming trend, we expect more of the same today. Of course, we can't rule out that a wet loose avalanche doesn't pull out a larger persistent slab, or perhaps the warming temperatures cause a cornice to fall and trigger a larger avalanche. These are just a couple more checks in the box that are holding the current avalanche danger rating.

The recent pattern of large to very large natural avalanches took a break after last Wednesday when a period of active wind-loading finally came to an end. As we moved away from that period of loading, the snowpack had time to adjust, and the sensitivity to human triggering dropped. That is, in part, reflected in the current likelihood rating for the persistent slab avalanche problem. The avalanche danger has also dropped a notch at lower elevations for a few reasons, most notably being that the potential avalanche size most commonly fits into the large category versus the very large and destructive category that is more common at higher elevations. 

Regioni coperte