Bollettino valanghe

Northwest Mountains

Crested Butte Avalanche Center
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Pericolo valanghe

Tue
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

The avalanche danger is Low this morning and could rise to Moderate as the day warms up.  On steep, sunbaked slopes, manage for shallow wet avalanches once the snow surface gets wet or starts to rollerball.  Larger slab avalanches are unlikely, but we can't completely rule out the threat of triggering a persistent slab on an unusually shallow or rocky slope or from cornice fall.   

Problemi valanghivi

  • Loose Wet

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

    Sunshine and warming temperatures will increase the threat of shallow wet avalanches involving the recent snow.  Watch for rollerballs, pinwheels, or natural sluffs to indicate developing instabilities first on east, then south, then west aspects.  Natural sluffs are most likely to initiate from very steep or rocky slopes.  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.  

    A small wet loose avalanche from earlier this week.

    (3/16/2024)

  • Persistent Slabs

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

    In the Northwest Mountains, high-consequence slabs breaking on older weak layers have become isolated and difficult to trigger. Any lingering persistent slabs are most likely triggered from an unusually shallow or previously wind-eroded slope where the total snowpack height is below average.  Large cornice falls could act as triggers as well. Persistent slab avalanches can be remotely triggered from low-angle terrain and break deeper and wider than you might expect.  The most problematic structures are on shallower slopes on the north half of the compass.  Mid to low-elevation, southerly aspects have the most trustworthy snowpack.  Slope angles consistently less than 30 degrees are a reliable way to avoid the problem when in doubt.  

    The crown of a very large persistent slab remotely triggered by snowmobiles on March 8.  This slope is west facing and eroded by seasonal winds, making for a shallower and more problematic snowpack than other slopes. 

Avalanche Discussion

In the Northwest Mountains, we bumped the danger back up to Moderate today due to increasing concerns for wet loose avalanches.  Periods of sunshine and greenhousing earlier this week spurred some wet loose activity up to D1.5 in size.  We have some uncertainty about whether today's wet instabilities will be hazardous enough to increase the danger: some slopes have run their course and easterly winds scoured other slopes.  However,  with significantly greater amounts of solar warming today relative to earlier this week, we erred on the side of caution to see how today's wet loose activity plays out.  Regardless, wet instabilities are fairly easy to recognize and avoid with spring travel protocols and terrain selection.  

On the shady side of the compass, you'll find drier snow but have to manage for the larger threat of slab avalanches breaking on older weak layers.  This issue is most concerning in our shallower Southeast Mountains.  The most recent example is a natural avalanche in Terminator Chutes on Saturday evening.  This observation from Saturday demonstrates how slopes with a deeper snowpack are relatively stronger and more trustworthy.  You can significantly reduce the risk of triggering a large avalanche by traveling where the snowpack is consistently deeper than about 200 cm (~6 feet).  If you're looking to step out into big alpine terrain this week, the deeper snowpack of the Northwest Mountains is generally a safer choice right now. 

Thanks to everyone who helped out or participated in the Al Johnson yesterday. We appreciate the community support and love to see all the great costumes!

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