Bollettino valanghe

Northwest Mountains

Crested Butte Avalanche Center
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Pericolo valanghe

Wed
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

Several noteworthy slabs released yesterday, including a remote trigger on Axtell, a large natural on Teo, and 3 people caught in a slide near Marble.  Our warmest and sunniest day since the storm ended will keep avalanche concerns elevated on sunbaked slopes, where small wet loose avalanches and warming storm slabs are possible.  The threat of triggering a large avalanche is most concerning on steep rollovers, heavily drifted terrain features, or where the snowpack was unusually shallow prior to the storm.  Collapses or shooting cracks are clear warning signs to stay off of steep terrain.  Don't linger below large cornices during today's warmup.  

Problemi valanghivi

  • Storm Slabs

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

    The weekend storm delivered 2 to 3 feet of mostly dense snow accompanied by periods of strong west/southwest winds.  The storm produced widespread natural storm slab avalanches on Saturday,  many of which were large enough to bury you.  Although storm instabilities are improving, several storm slabs were triggered yesterday.  Solar warming today could destabilize slabs or in rare instances, meltwater could trigger a wetting storm slab.  You are most likely to trigger a lingering storm slab up to several feet thick in terrain that is very steep or unsupported, especially where winds have drifted the snow.  Consider terrain characteristics and consequences before riding in avalanche terrain.    

    This large and dangerous storm slab released on Monday afternoon (3/13) due to solar warming.  

  • Loose Wet

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

    In very steep or rocky terrain, watch for shallow wet loose avalanches once the sunshine and warming temperatures wet the snow surface.  Rollerballs, pinwheels, and sluffing snow indicate the snow surface is becoming unstable.  Although most sluffs should be small today, they could cause harm if they push you into trees, rocks, or gullies, or if they trigger a larger slab avalanche.  Avoid the problem by moving to colder aspects or mellower slope angles.  

    Small sluffs like these are signs of developing wet loose avalanches.  

Avalanche Discussion

We're keeping storm slabs on the list for another day following several newsworthy slides yesterday.  Three skiers were caught and carried in a large (D2.5) storm slab near Marble while ascending a steep rollover. All three deployed their airbags which helped them survive.  On Mt. Axtell, a skier remotely triggered a 2-foot storm slab (D1.5) above a steep, unsupported slope.  And on the South face of Teo, a large wind-drifted storm slab ran in the afternoon sun (D2.5).    Rapid surface warming yesterday likely played a role in some, if not all, of these slides.  More sunshine and warmer temperatures today will keep the concerns for warming slab weirdness going, and promote the development of small wet loose avalanches.  Note the terrain characteristics of yesterday's slabs in the gallery below.  As the threat of storm slabs diminishes after a storm, lingering instabilities are most common on steep rollovers, heavily drifted features, or unsupported slopes.

The snowpack becomes more complex with a higher potential for triggering a persistent slab in the Southeast Mountains, where snow depths have remained shallower all winter.   We've expanded the distribution rose of the persistent slab problem after documenting several persistent slabs on the south/southwest face of Teo yesterday.  Persistent slab activity and signs of instability in the past month have been infrequent enough that it is difficult for us to diagnose a specific pattern, but the most common theme has been wind-drifted slopes during or shortly after storms or wind events.  This weekend's system brought an impressive amount of snow to some lower elevation or windward areas that are typically snow-starved.  These areas have a shallow and weaker snowpack that will be slower to heal after the storm and could be developing into a new persistent slab problem.  This video from Sunday describes the setup. Regardless of where you are in our forecast zone, if you are on terrain that has been unusually shallow, and thus weaker, all winter, be extra cautious of persistent slab behavior. 

The next storm will bring increasing avalanche danger tomorrow that peaks overnight on Wednesday.  A new generation of dangerous storm instabilities could develop tomorrow at higher elevations in Northwest Mountains and spread to the shallower zone overnight on Wednesday as the storm intensifies.  Stay tuned for changing conditions.    

Events:  The Al Johnson race is Sunday, March 19. Information and registration are here.  Day of race registration and bib pick up 9-11 a.m. at the Adventure Center in Mountaineer Square. Proceeds go to the CBAC.

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