Bollettino valanghe

Northwest Mountains

Crested Butte Avalanche Center
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Pericolo valanghe

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

In sintesi

A handful of large naturals have run during the past two days from solar warming on sunbaked slopes.  If cloud cover fails to develop by this afternoon, we could see more of the same today.  You are most likely to trigger a large avalanche in wind-affected terrain with variable snow depths, rock bands, or shallow spots.   You can find safer riding and higher quality snow in wind-protected, shady terrain where the snowpack is consistently deeper than about 4 or 5 feet deep.  

Problemi valanghivi

  • Persistent Slabs

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

    January storms formed slabs averaging 2 to 4 feet thick over widespread persistent weak layers lower in the snowpack.  Persistent slab avalanches have the potential for wide propagation and remote triggering,  and may not give any warning signs. We've observed a recent uptick in natural persistent slabs on higher elevation southerly and westerly facing terrain over the past few days, where the problem appears to be most reactive right now.   The easiest and most reliable way to manage this problem is to ride on slopes consistently less than 30 degrees in steepness.  Other strategies for reducing your risk include riding on slopes where the problem has recently avalanched away, avoiding trigger points where the snowpack thins near rock outcrops or wind-eroded terrain features, or traveling where the snowpack is consistently deep (>150cm) and uniform. 

    A large persistent slab that ran 1/29 on the southwest side of Afley.  

  • Loose Wet

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

    As the snow surface gets wet later today, shallow wet avalanches can be triggered or could run naturally from very steep, sunbaked slopes, especially near rock bands.  Look for rollerballs, pinwheels, or pushy wet snow under your machine or skis to warn you of the developing problem.  Wet loose avalanches can cause trouble if they push you into a terrain trap or if they trigger a larger persistent slab.  There is isolated potential for large wet avalanches to occur today, either a long-running wet loose avalanche or a wet slab from a hot, rocky slope. Choose lower slope angles or colder aspects to avoid the issue.  

    Small wet loose activity like this was common yesterday, especially near and above treeline.  Expect more of the same with today's warmer temperatures.  

Avalanche Discussion

Natural activity continued yesterday, with a handful of D1.5 to D2 slab avalanches observed on the Aspen side, and more slabs observed on the CB side that ran sometime in the past day or two.  We've got one more day in the solar oven. Temps are expected to stay a little cooler with some midday cloud cover, so we're expecting a downturn in natural activity compared to the last two days.  Human triggering a large avalanche remains a concern on all aspects, especially in wind affected terrain or shallower parts of the forecast zone.  Yesterday, a skier was caught in a large avalanche in the San Juans on a north-facing slope.  Check out a photo of the avalanche and note how the slab is variable in thickness; the skier triggered the avalanche after crossing a "punchy" or thin part of the slab.   Now almost two weeks since the loading event ended, there are fewer slopes capable of producing this type of avalanche, but those lingering troublemakers are hard to identify.  Traveling in terrain where the snowpack is consistently deep and uniform is one strategy to reduce your risk. 

Although the current warmup is adding another layer of complexity to our persistent slab issues, it will help us in the long run.  Slopes where meltwater is moving deeper into the snowpack will be stronger once that meltwater remains frozen in the form of thick crusts.  With cloudier and cooler temperatures tomorrow, we will finally start chipping away at the distribution of our persistent slab problem where crusts are thick enough to significantly reduce the chance of human triggering.  Unfortunately, we have new persistent weak layers forming on the snow surface right now that will be a problem with heavy snowfall coming this weekend and beyond.  Take note of the surface hoar and near-surface facets now before they get buried.     

Events: Our next Fireside Chat is this Sunday, February 4 at 6 p.m. at High Alpine Brewing Company in Gunnison. A local snowmobiler will talk about his experience with an avalanche burial and rescue while snowmobiling last year.

Regioni coperte