Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
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Avalanche danger

Fri
Alpine
1 · Low
Treeline
1 · Low
Below
1 · Low
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Out of date — this forecast expired 8 months ago. You’re viewing past conditions, not the current bulletin.

Highlights

Most slopes offer safe travel without the threat of avalanches, with only a few inches of new snow expected today.  Stay alert for old, hard drifts that formed earlier this month at upper elevations and in extreme terrain (e.g., Irwin, Marble).  Today's weather forecast is highly uncertain; if you encounter around 8 inches of new or windblown snow, or if you experience rain at the lowest elevations on northerly slopes, the danger is increasing.

Avalanche problems

  • Persistent Slabs

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

    An extreme wind event last week formed a few thin, hard slabs scattered across all elevations, in concave catchments and behind abrupt transitions in the terrain. Where these drifts formed over facets on colder aspects, you might still be able to trigger one, and they're stiff enough to knock you off your feet.  Look for firm, rounded snow surfaces to identify potential features of concern. 

    Snowfall and wind drifting in early December formed slabs up to a couple of feet thick over facets near the ground.  These weak layers are most widespread on the northern half of the compass. Mild weather through the middle of December has helped the snowpack adjust to its current load, and in many areas, the slabs have decayed or been scoured away by winds. The last documented avalanche on these old, weak layers was accidentally triggered on 12/14.  Similar instabilities will be very rare, but not impossible.  

    An example of a thin, hard slab over sugary facets. The resulting avalanche would be small in size, but the hard snow surface could easily pull you off your feet or push you into a tree. 

Avalanche Discussion

It appears Santa put us on the Naughty List this year.  Weather models continue to predict less snow today, even though ample moisture streams into the region.  Snowfall totals on Christmas Day likely amount to just a few inches, not exceeding 6 before sundown.  With this forecast, the danger rating remains at LOW.  A new avalanche problem is not likely to form today.

Without substantial new snow, avalanche hazards are rare across the landscape and patterned by previous wind drifting.  Avalanche activity has been scarce in the last week, limited to a few small, hard slabs following last week’s extreme wind event.  Where these slabs formed over weak snow surfaces on colder aspects, they remain a small and stubborn concern in high-consequence terrain.  The thicker slabs that formed in early December have had two weeks of quiet weather to adjust or decay, and most slopes are expected to be unreactive. Recent reports of collapses and shooting cracks from Hunter Hill are a reminder that these older slabs still have the potential to surprise if you find the wrong slope.

Uncertainty lingers for today's weather forecast. I don't personally have any memory or experience with such a warm and wet storm in the dead of winter.  Models suggest just a couple of inches around the forecast area before sunset, but the anomalous amount of moisture could overproduce.  Stay alert for changing conditions today, and the slight chance of a new slab to form if 8 inches or more accumulates.  If the storm were to exceed forecasts, the hazard would likely increase on wind-drifted terrain first and possibly protected northerly slopes where the new snow would fall on a very weak, faceted snowpack.  Finally, the unusually warm weather could produce some rain at the lowest elevations (a light sprinkle started in town around 5:45 am).  A moderate rain shower could produce Wet Loose avalanche conditions, particularly on low-elevation northerly slopes due to the highly faceted snowpack. 

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