Avalanche forecast

Southeast Mountains

Crested Butte Avalanche Center
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Avalanche danger

Sun
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

Chrismas Day has arrived with very dangerous avalanche conditions thanks to the recent historic storm. Tell your friends, tell an out-of-towner, and remind yourself that these avalanche conditions are DEADLY. Wind-loading may contribute to additional natural avalanches releasing today, and it is possible for those avalanches to reach below treeline elevations or valley bottoms. These avalanches would be very large in size and destructive. Human triggering a large to very large avalanche also remains likely. Travel in avalanche terrain is not recommended.

Avalanche problems

  • Storm Slabs

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

    Storm totals have stacked up to multiple feet of snow, while SW winds have added additional feet of snow onto wind-loaded terrain. This avalanche problem could release within the storm snow, or multiple feet deep on the old snow surface around the compass. Expect unusual avalanche conditions. The travel advice is avoidance. 

     

    An example of an avalanche earlier this season, that propagated widely, which gives a good representation of how far the current Storm Slab avalanche problem may propagate due to the cohesiveness of the slab.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2–3

    Persistent weak layers exist as facets near the ground, and in the middle of the snowpack as buried surface hoar and additional weak faceted layers. Many steep slopes avalanched earlier in December and developed an entirely faceted snowpack. With the exceptionally dense and heavy storm snow resting above these weak layers, you can expect natural avalanche activity and a high likelihood of human-triggered avalanches. Anticipate that you can remotely trigger a dangerous avalanche from below or adjacent terrain. Avalanches can break wide and connect through terrain features particularly for areas that receive the most snowfall or where southwest winds have drifted snow into larger, thicker slabs on leeward terrain. The travel advice is avoidance. 

    This widely propagating persistent slab ran naturally on December 10th on Mt. Axtell that illustrates the wide propagation potential as well as the impressive destructive size you expect today.

Avalanche Discussion

The Santa Slammer has made its way into the record books. This was the recent storm that started on Thursday, peaked on Friday and slowed down overnight. Looking specifically at the Schofield Pass Weather station, the 24hr snow water equivalent (SWE) totals landed this storm in the 90th percentile of all major storms on the historical record. The biggest midnight to midnight SWE increase at Schofield was 3.9 SWE in 2010. The Santa Slammer recorded a 3" SWE increase from Thursday Midnight to Friday Midnight. However, if we pick the greatest 24" SWE increase during the Santa Slammer we land at around 4" SWE. Historic.

As we are emerging from this storm on Chrismas Morning, avalanche forecasters are feeling entrenched and have no confidence pulling back avalanche danger ratings. Historic storms often lead to historic avalanche cycles and/or unusual avalanche conditions. We are entering a lull in the loading and this has allowed the below treeline avalanche danger rating to drop to CONSIDERABLE. A level of uncertainty and continued wind-loading at upper elevations will keep the avalanche danger at HIGH. Natural avalanche activity could continue today and some of those avalanches could impact below treeline elevations and valley elevations. Those avalanches would be very large in size, destructive, and DEADLY. 

A note on potential, unusual avalanche behavior. The new slabs are so thick, and deep, that many test slopes may not produce the results that you expected. Those slopes may be too small and the slabs may have good support which could lead to a false sense of stability. 

A quick look at storm totals since Thursday. Schofield Pass 5.5 SWE. Irwin 3.5 SWE (estimated). Upper Taylor Snowtel 3.4 SWE. This was a warm storm that produced high water to snow ratios and dense heavy snow. Actual snow total numbers are still adding up to multiple feet of snow and have more than doubled the total snowpack. 

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