Avalanche forecast

Southeast Mountains

Crested Butte Avalanche Center
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Avalanche danger

Mon
Alpine
2 · Moderate
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

A record-setting warm-up is causing dangerous wet avalanche conditions.   The threat of large natural and triggered wet avalanches will increase as the day warms up. Start and finish your tours early and move to mellow terrain before thin surface crusts thaw into wet mush.  This is the warmest day following the weakest freeze of the week.  Wet loose avalanche activity will continue to escalate starting early in the day, and the threat of dangerous wet slabs is increasing.  There is still a lingering chance of triggering a large, dry slab avalanche on northerly aspects as well.  

Avalanche problems

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Wet loose activity has been increasing in size and expanding to more terrain during our warmup.   Warm temperatures and sunshine will cause the upper snowpack to lose cohesion throughout the day, making natural and triggered wet loose avalanches likely in steep terrain.  Rollerballs, pinwheels, or ankle-deep slushy snow are warning signs that steep slopes are unstable.  Move to a colder aspect or lower angle terrain to avoid this problem once it develops.  Wet loose avalanches are growing to dangerous sizes that are large enough to easily injure or bury you in some terrain.  With a poor overnight freeze, expect wet loose activity to begin early in the day on northeast and east aspects before moving south and then west as the day progresses.  

    3/26:  A large wet loose avalanche below Gibson Ridge.

  • Wet Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    Consecutive days of meltwater production and a poor overnight refreeze are increasing our concerns for natural or triggered wet slabs.  As meltwater drains into weak layers, it can compromise their strength and cause a dangerous wet slab to release.  Our most concerning aspects are where our mid-winter weak layers are transitioning from dry to wet this weekend: east and west aspects.  There is also potential for wet slabs on higher elevation southerly aspects.    Avoid travel on steep terrain and in runouts once the snowpack becomes unsupportive and trenchy.  Use extra caution below sunbaked cirques or rock bands, which tend to exacerbate meltwater.

    A large wet slab avalanche ran naturally on 3/26 in the Northern San Juans.  When the San Juans start seeing wet slabs, we are usually quick to follow.  

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    On the northern half of the compass, you can trigger a slab avalanche that breaks up to several feet thick on weak faceted snow that was buried last month. Slabs can be triggered remotely from below or adjacent slopes.  Collapsing and cracking are clear signs of instability, although direct feedback on this problem has become less frequent.  In the Southeast Mountains, slopes holding a snowpack deeper than 1 meter and less than 2.5 meters are most suspect.  When in doubt, head for lower consequence terrain, or slope angles in the lower 30-degree range and less.  Large cornice falls or wet loose avalanches caused by warming temperatures today could also act as natural triggers for this problem.   When in doubt, head for lower consequence terrain or slope angles in the lower 30-degree range and less. 

    This large persistent slab avalanche was remotely triggered on 3/18. 

Avalanche Discussion

This video helps illustrate today's dangerous conditions. Yesterday, we observed wet loose avalanche activity continuing to ramp up in size and distribution, with activity spanning almost the entire compass except for due north.  With a poor refreeze overnight and some cloud cover shifting the energy balance to northerly aspects, I'm expecting wet loose activity to be even more active today, especially on slopes that have been transitioning from dry to wet snow over the past couple days.  Large wet loose avalanches like the one that ran on Gibson Ridge yesterday will become more common.   A weak surficial freeze will shorten the window of morning stability compared to previous days.

Although we've yet to observe significant wet slab activity locally, conditions are just now becoming optimal, with multiple days of exceptionally warm temperatures and mediocre refreezes.  This small slab yesterday near Copper Creek and this large wet slab in the Northern San Juans could be precursors to more or larger wet slab activity here today.   Predicting when and which specific slopes will produce wet slabs is very challenging because meltwater flows through the snowpack in unusual and unpredictable ways.  My biggest concerns are east, west, and higher southeast aspects which are all in the phase of transitioning from previously dry to wet.  Although wet slabs are most common after the snow surface becomes saturated and unsupportive, some can be triggered when the upper snowpack is not giving warning signs.  It's prudent to give suspect aspects an extra buffer over the next couple of days until the meltwater faucet has turned off.    

With our primary concerns shifting towards wet avalanches, it's easy to forget that northerly aspects are still capable of producing large dry or mostly dry slab avalanches on some slopes.  Just a few days ago, a skier had a close call with a deadly persistent slab just north of our forecast area in Express Creek.  This destructive avalanche in the San Juan Mountains yesterday appears to be a dry, hard slab that was triggered by a wet loose avalanche.  Similar concerns exist in our forecast area, especially where the snowpack is shallower.    

 

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