Bollettino valanghe

Southeast 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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In sintesi

The chances of triggering a dangerous slab avalanche slowly decrease but the consequences remain deadly.  A close call near Snowmass on Monday illustrates the lingering potential for dangerous human-triggered avalanches.  Use caution on the north half of the compass with a snowpack depth of around 3 to 5 feet or on rocky slopes with a variable depth.  You can find safer conditions where the snowpack depth is consistently 6 feet deep or more.  Warming temperatures and sunshine likely create wet snow avalanche problems on sunbaked slopes at lower elevations.  Rocky areas and terrain with dust at the surface could produce larger loose avalanches as the snowpack wets by the afternoon.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    In the Southeast Mountains, high-consequence slabs breaking on older weak layers are becoming more difficult to trigger but remain a concern on the north half of the compass, or potentially on a few southerly slopes above treeline.  The most prominent weak layers are surface hoar buried a couple of feet deep and depth hoar near the ground.   Persistent slab avalanches can be remotely triggered from low-angle terrain and break deeper and wider than you might expect.   Triggering avalanches are unlikely on mid to low-elevation, southerly aspects, or areas where the snowpack is consistently deeper than 200 cm.  Slope angles consistently less than 30 degrees are a reliable way to avoid the problem.

    A large persistent slab on Mt. Crested Butte that ran on 3/16.  This slope is shallow, variable in depth, and on the north half of the compass: a combination of ingredients you want to avoid.  

  • Loose Wet

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

    Sunshine and warming temperatures will increase the threat of shallow wet avalanches involving surface snow.  Watch for rollerballs, pinwheels, or natural sluffs to indicate developing instabilities first on east, then south, then west aspects.  Natural and triggered sluffs are most likely to initiate from very steep or rocky slopes or places with a dirty snow surface.  Be careful in or above consequential terrain once the snow surface gets wet or sticky.  You can avoid triggering wet loose avalanches by riding on slope angles less than 35 degrees or moving to colder aspects.  

    (3/18/2024)

    Recent wet loose avalanches from easterly terrain on Whetstone.  This is a good representation of the potential size.

    Photo: Zach Guy

Avalanche Discussion

The Persistent Slab problem is the primary issue on Wednesday.  Recent avalanche activity and observations suggest that shallower snowpacks on the north half of the compass represent the most likely place for you to trigger a dangerous slab avalanche.  You are more likely to encounter a shallow snowpack in the Southeast Mountains, but a thin snowpack can still be found in isolated places in the Northwest Mountains.  A recent natural avalanche in Terminator Chutes on Saturday and a triggered avalanche resulting in a very close call near Snowmass on Monday highlight the issue.  Both of these avalanches occurred in terrain with shallower snowpack due to less seasonal snowfall and/or previous wind erosion.  You can reduce your risk of triggering a slab avalanche by traveling where the snowpack is consistently deeper than 200cm (~ 6 feet) and by avoiding terrain with obvious trigger points.

Wet snow concerns exist in both forecast zones due to seasonally warm temperatures and sunshine.  Wet avalanche problems are expected to remain small with this observation from Monday illustrating the current character.  A few places could produce natural sluffs today; very rocky areas are warmer than open slopes and the lowest elevation sunny slopes where warmer temperatures more effectively wet the upper snowpack.  Slopes with a dusty, brown surface will warm faster and may produce larger wet loose avalanches.  Ideal conditions for riding have just enough softening for good turns, but the snowpack should remain supportive below.  If you find punchy and mushy snowpack head to a cooler aspect or lower angled terrain.

As meltwater infiltrates the snowpack, concerns for Wet Slab avalanches slightly increase.  An observation from near Snodgrass suggested that east and west aspects at low elevations have meltwater draining into a winter-like snowpack.  Rocky, bushy, and/or dusty surfaced terrain often moves meltwater faster than open, white snow slopes.  Wet Slabs are difficult to predict and manage.  A good rule of thumb is to start your day early and move off east and west aspects with wet snow surfaces earlier than usual.  This isolated and unlikely threat will linger until cooler weather arrives this weekend and meltwater production ceases.

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