Bollettino valanghe

Southeast Mountains

Crested Butte Avalanche Center
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Pericolo valanghe

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

In sintesi

Use caution at higher elevations for the lingering threat of triggering a relatively small wind slab.  Steer away from recently windloaded features in high consequence terrain.  On northerly aspects near and above treeline, aim for deep and uniform slopes to reduce the chances of triggering a low-likelihood but high-consequence avalanche breaking on old weak layers.  Manage for shallow sluffing in the recent snow where it gets moist or wet in the sun.   

Problemi valanghivi

  • Persistent Slabs

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

    High-consequence persistent slab avalanches have become isolated and difficult to trigger.  The most problematic terrain is on high elevation, northerly aspects in areas with relatively shallow snowpacks (<175 cm).  Old facet layers are weaker and easier to impact in steep rocky slopes with variable snow depths.   This video sums up an example of this type of terrain.  You can reliably avoid the problem on the southern half of the compass, where the snowpack has transitioned to more of a springlike structure.  

    Persistent slab avalanche crowns spanning steep, rocky terrain. This avalanche ran sometime during the late March storm cycle and wind-loading event.  

  • Wind Slabs

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

    Strong winds shifting from the southwest to northwest accompanied 5" to 10" of snow on Saturday.  Although most wind slabs are healing up now, there could be lingering instabilities at higher elevations, especially on colder aspects where slabs formed over weaker snow surfaces.  Look for smooth-looking and stiff-feeling wind slabs on the lee sides of ridgelines and cross-loaded terrain features to identify the problem. In high-consequence terrain, steer around suspect features and choose softer, more wind-protected snow.  

    A wind slab avalanche triggered by explosives on Mt. Crested Butte on Sunday.    

Avalanche Discussion

This looks like an excellent week for tackling spring objectives in more complex terrain.  Slab avalanche concerns will become increasingly rare as the week goes on.  Saturday's blustery storm left some relatively small wind slabs (generally up to D1.5) scattered across higher elevations.  They're now on the mend, and should be phasing off the list by tomorrow.  Stay cautious in high-consequence terrain where a wind slab would take you for a traumatic ride.  Use surface textures to identify problematic features and monitor potential wind slab size by probing down to the hard crust or old interface below.

Following a surge in persistent slab activity during our late March storm cycle, signs of instability and stability tests have shown significant improvement in the last week. Our last persistent slab was triggered on April 3rd.  Last week's warmup sent meltwater into the snowpack on all but the high northerlies, effectively narrowing the distribution to those coldest slopes.  The most recent weak layer interface (March 23rd near-surface facets) is now buried several feet deep and has been rounding and gaining strength since the late March storm cycle ended. Persistent slab avalanche concerns are transitioning away from this specific interface, and back to more isolated areas with unusually shallow snowpacks.  If you are riding on high, northerly terrain, seek out slopes with deep and uniform snow depths to reduce your risk of a low likelihood, high-consequence avalanche.  

The most recent snow will transition from dry powder to wet snow in the next few days causing shallow wet loose instabilities on sun-baked slopes.  Unlike last week's warmup, entrainment potential looks to be limited to just the fresh snow over hard crusts below.  In most areas, storm totals were meager, and wet loose concerns will be very small and isolated. In favored parts of the Northwest Mountains, there's upwards of 8" or 10" of new snow available to sluff, which will require your attention in high-consequence or extreme terrain.  Use sluff management techniques or time your travels to avoid very steep slopes after they get too warm and wet.  

Regioni coperte