Lawinenlagebericht

Northwest Mountains

Crested Butte Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist last year abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

The pattern of avalanche activity over the past few days showcases our concerns well.  You can trigger shallow wet avalanches as the day warms up on sunbaked slopes.  Travel early for better stability on sunny aspects or move to mellower terrain after the upper snowpack gets wet and starts sluffing.  Lower likelihood dry slab concerns linger on higher, colder aspects.   

Lawinenprobleme

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Manage for shallow wet avalanches once the upper few inches of snow get wet.  Today's wet loose avalanches should entrain just last week's new snow, and most are relatively small in size.  Long, steep terrain could grow larger or a few slopes could propagate wider as thin wet slabs.  Rollerballs, pinwheels, and ankle-deep wet snow indicate decreasing stability.  Move to less consequential terrain as the problem develops.  You can avoid wet avalanches by traveling early while snow surfaces are frozen or moving to colder aspects as the day warms up.   

    These recent wet loose avalanches on Gothic exemplify the average size you can expect to encounter later today. 

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2.5

    New and windblown snow last week formed soft slabs about 1 to 2 feet thick, especially on terrain features favored by westerly winds.  These slabs have bonded well in most terrain, with some potential exceptions where they formed over a faceted crust.  This buried weak layer is variable across the landscape.  Carefully assess slab size, bonding, and terrain consequences before riding in steep leeward terrain.   Problematic slabs are rare below treeline and have improved on sunnier aspects from ongoing warming.     

    There's a rare chance you can still trigger a deep persistent slab on high, northerly aspects where the snowpack remains winter-like. Terrain where the snowpack is unusually shallow due to wind effects or previous avalanche activity is most concerning.  Choose deeper, more uniform snowpacks over thin, rocky areas to reduce your risk.   

    This persistent slab was triggered by a shallow wet loose avalanche yesterday on Teocalli Mountain.  

Avalanche Discussion

Wet loose avalanches should remain the most active problem on the menu today.  We've documented numerous small (D1 to D1.5) wet loose avalanches on east, south, and west aspects involving last week's new snow. We're showing D2 potential in the Northwest Mountains, where there's enough recent snow to grow large in isolated areas, such as this long-running wet loose near Marble.   Activity has been concentrated near and above treeline where there's more fresh snow for entrainment and more exposed rock bands that act as natural triggers.  If surface warming creeps around the compass to colder aspects below treeline, there's enough recent snow at these lower elevations to be productive, especially north and west of town.  An uptick in wind speeds and some high cloud cover today may cause a minor downturn compared to yesterday's natural activity. 

Our wet loose problem is fairly easy to recognize and manage.  There are still some surprise slab avalanches lurking out there as well.  Yesterday, forecasters on Teocalli found unstable stability tests and triggered a persistent slab by sending a shallow wet loose onto a previously drifted slope.  We've been finding the problem to be hit-or-miss on colder aspects.  The warm weather is narrowing the distribution of the problem and is favorable for strengthening in the upper snowpack. There's a chance these same structures could produce thin wet slabs as meltwater reaches the faceted crust that has been the culprit in handful of human-triggered avalanches in the Elk Mountains in the past week.  By managing for wet loose instabilities, you can also avoid the isolated threat of a shallow wet slab.  It's been a few weeks since we've observed a dry slab avalanche breaking on deep, weak layers (ex. Axtell).  A lack of major loading events and warmer temperatures in recent weeks are working in our favor.  The isolated and high-consequence threat remains on high, northerly terrain where the snowpack has remained dry all spring.  For example, last week a skier in the San Juans was surprised when they triggered a shallow wind slab that stepped down and produced a very large avalanche. 

Events: CBAC's Party for the People is at the Talk of the Town next Thursday.  Come celebrate the end of the season with us!  (Don't worry, we'll be forecasting for at least a few more weeks.)

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