Boletín de aludes

Gunnison

Crested Butte Avalanche Center
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Peligro de aludes

Tue
Alta montaña
2 · Moderado
Límite del bosque
1 · Débil
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 2 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

With up to 7 inches of recent snow and gusty west-to-southwest winds, you may encounter sensitive drifts at upper elevations.  Most triggered avalanches would involve just the recent drifted snow, but there's an outside chance an avalanche could break deeper into the snowpack on older layers.  Steer away from leeward terrain features below ridgetops and cross-loaded gullies where you encounter recent drifting to reduce the chances of triggering a slab avalanche.  Wind-sheltered areas offer lower-risk options. 

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–1.5

    Up to 7 inches of snow accumulated in the past few days. Recent westerly winds averaged in the 20 to 30mph range with notably stronger gusts near and above 12,000ft.  Above treeline slopes are the most likely places to encounter the problem, but isolated near treeline slopes may have the problem too.  The specific locations to keep an eye out for new slab development would be on the leeward sides of ridgelines and in crossloaded gullies. Consider utilizing small test slopes to help identify the potential size and how reactive this avalanche problem is in your area. 

    An example of shooting cracks along a wind-loaded ridgeline from earlier this winter. 

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely
    Tamaño
    1–2

    Old hard slabs up to several feet thick have become isolated and difficult to trigger. You are unlikely to see signs of instability before triggering an avalanche that breaks on old weak layers.  The most likely trigger points would be where these hard slabs thin near their margins, on convexities, or near rocky areas.  Recent snowfall and wind drifting may have obscured the surface clues, making identification of old, hard slabs difficult.

    This hard slab was triggered near Pearl Pass on 2/3.  This location is just beyond the CBAC's Southeast Mountain forecast boundary. 

    Photo: CAIC

Avalanche Discussion

Mother Nature provided a much-needed refresh to surface conditions the past few days.  Irwin and observers in the Ruby Range reported about 7 inches of storm snow from the past few days.  Areas closer to town and Mount Crested Butte snagged less, with around 3 inches.  We have little data from the higher terrain in the Southeast Mountains near the tops of the East River, Brush Creek, and Cement Creek drainages, so there could be larger totals in those areas.  Unfortunately, the wind has been equal opportunity at upper elevations, commonly blowing 15 - 30 mph with gusts exceeding 50.  Weather forecasts on Monday called for an additional inch or two and continued gusty winds.  Expect Monday's weather to transport snow to leeward terrain features and help recent drifts grow in size and maintain sensitivity.

Winds don't have a lot of snow to form Wind Slabs, but just enough for some terrain to be problematic, particularly features with a large fetch.  On Sunday, forecaster fieldwork from Purple Ridge suggested that not all leeward features have sensitive slabs, but glassing around the range found evidence of significant wind transport in some zones.  Carefully read the terrain if you travel at upper elevations and look for scoured fetches and stiffer, pillow-shaped deposits in leeward terrain features.  Avoid these drifts to greatly reduce the risk of triggering an avalanche.  The wind slab problem was removed from the near treeline elevation band due to less wind effect, but you may find a fresh slab here, just less frequently.

The old Persistent Slab problem is unlikely due to an isolated nature across the landscape and a difficult-to-trigger sensitivity.  You can find old, hard slabs of snow below ridge tops, cross-loaded in gullies, and pressed into concave features. Locally, a few slabs released during the warmup at the start of last week.  More recently, a couple of slab avalanches were triggered in the Aspen area on Monday. However, this area received more snow than the CBAC forecast zone.  After failing in the recent storm snow, one of these slides stepped down to the older Persistent Slab problem.  Although unlikely, a similar avalanche could happen around this area.

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