Avalanche forecast

Gunnison

Crested Butte Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Wet and warm weather is creating unusual conditions in the backcountry. Precipitation over the last 36 hours has fallen as both rain and snow, adding additional load to buried weak layers on the northern half of the compass. Strong west to northwest winds continue transporting snow onto the lee sides of terrain features, and destructive natural avalanches have been observed as recently as Tuesday. Dangerous avalanche conditions persist, and conservative travel is recommended to manage these complex conditions.

Avalanche problems

  • Persistent Slabs

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

    Slabs over buried weak layers 2 to 4 feet thick vary from stubborn to reactive under the weight of humans, and we can't rule out additional natural avalanches from contained windloading.  These slabs are stiffening and often do not show obvious warning signs before someone triggers a large and destructive avalanche. The north half of the compass has the most fragile weak layers buried in the middle and bottom of the snowpack and is most likely to produce remote-triggered, widely propagating, and destructive avalanches from steep or adjacent flat terrain (see several videos illustrating this).  Some higher-elevation southerly terrain also harbors problematic structures.  Manage today's persistent slab problem by choosing lower-angle and more conservative terrain without steeper overhead hazards on the aspects highlighted above.

    Below ~10,000ft, this avalanche problem has a moist to wet slab from recent rain and warm temperatures. A triggered avalanche may run more like a wet slab, but the above travel advice will remain the same. 

     

    A pair of large persistent slabs below Scarp Ridge, which likely ran during increased winds on Tuesday.  

    Photo: Irwin Guides

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    A little new snow and gusty winds are forming shallow slabs that might be sensitive to triggers on heavily drifted slopes near or above treeline.  Slabs will typically be small, but could be problematic if they push you into a terrain trap, or worse, if they step down and trigger a much larger persistent slab. Likewise, warm temperatures and wind drifting can cause cornice failures, which can trigger larger, persistent slabs.   Avoid these issues on wind-eroded or wind-sheltered terrain.  

    Wind transport began on Tuesday and continues today.

Avalanche Discussion

Observers yesterday noted rain crusts that extended well above 11,000ft, and found a moist to wet snow surface below ~10,500ft. Last night, 9,000ft weather stations stayed above freezing while 10,000ft weather stations dropped below freezing. The freezing level may have landed somewhere around 9,700ft. A mostly cloudy sky overnight will also have limited the snowpack's ability to lose heat. Free water is not expected to be plentiful enough to commonly be draining into dry persistent weak layers on the northern half of the compass and creating wet slab avalanche conditions, but the moist to wet snow in those slabs will exhibit a hybrid wet flowing motion for a triggered avalanche. Those surface crusts will make finding good skiing and riding more challenging today, until warming temperatures help soften the snow. 

More destructive natural avalanches were observed on Tuesday, and are a reminder that our snowpack remains unstable. There was no visibility to observe if additional avalanche activity occurred on Wednesday. This steady string of large remote triggers continues to paint the picture of the dangerous avalanche conditions. Our forecast team has continued to travel conservatively while tracking avalanche conditions and has avoided some terrain we typically use to gather feedback because of the fear of a widely propagating, potentially destructive avalanche releasing without obvious warning signs. 

SWE (snow water equvelent totals for the last 36hours average .4 SWE at remote weather stations across the forecast area. Hand measurements at Irwin, recorded .65 SWE as of yesterday afternoon. This is notable, becuase it shows additnal load is being added to burried persistent weak layers. Slabs above those weak layers have become strong enough that they don't often produce obvious signs of instability. The thinner slabs more commonly found in the SE Mountain forecast area were more commonly producing obvious signs of instability earlier this week, but even those areas may be starting to quiet down. While conditions may be quieting down in some areas, the buried weak layers are not gaining significant strength, and that is where the scary accident potential lies. 

Ideally, we'll see a nice freeze tonight with a mostly clear sky. That would help lower the avalanche danger at lower elevations. While upper elevations need to wait until after we see an end to additional wind-loading, and burrie weak layers further have more time to adjust to their load. 

Regions covered