Bulletin d’avalanche

Northwest Mountains

Crested Butte Avalanche Center
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Danger d’avalanche

Fri
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
4 · Fort
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Périmé — ce bulletin a expiré 5 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

An Avalanche Warning is in place for very dangerous conditions as snowfall piles up today.  The exact timing of HIGH avalanche danger today is uncertain but with 6 - 12+ inches forecasted for daylight hours accompanied by strong west-southwest winds avalanche conditions will certainly worsen.  You can easily trigger very large slides and long-running natural avalanches may become likely.  Avoid avalanche terrain and stay out of avalanche runout zones to protect yourself against unusual avalanche activity. 

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely
    Taille
    2.5–4

    Large and destructive avalanches are sensitive to human triggers and natural avalanches may become likely today.  These widely propagating and long-running avalanches will break 5 to 8 feet thick or more on weak layers near the bottom of the snowpack.    Persistent slabs are most common on northerly and easterly aspects, where these buried weak layers are most fragile and slabs are more widespread. The distribution rose also includes south to west aspects where there may be potential for crusts near the bottom of the snowpack to collapse. Given how thick these slabs are, you may not observe any obvious signs of instability. For example, two large avalanches were human triggered on Mt Emmons on Saturday or this recently observed avalanche near the Red Lady skin track. 

    A persistent slab triggered from a low angle ridgeline on Red Lady Glades. The slide broke 3 to 4 feet deep and ran far.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1.5–2.5

    Around a foot of fresh snow accumulated in the past 24 hours, another 12+ inches forecasted today, and gusty southwest winds have created instabilities in the upper snowpack.   Slabs will be most sensitive near and above treeline where winds have stiffened or drifted the snow into more cohesive or thicker slabs.  New snow instabilities are easier to recognize: you are likely to see cracking in the snow or get feedback on steep terrain.  However, any moving snow in the upper snowpack could step down and trigger a larger persistent slab.  You can avoid triggering storm slabs by riding on slopes less than 30 degrees.  

    An example of an avalanche earlier this season, that propagated widely below a wind-loaded ridgeline.  

Avalanche Discussion

This video gives a brief snowpack history and context as to why avalanche conditions are so dangerous right now.  A historically significant stormy period is entering the eighth day of accumulating precipitation with the Schofield Snotel site registering 11 inches of Snow Water Equivalent (well over 10 feet of snowfall) and CBMR accumulated 75 inches of snow since December 23rd.  Forecast models suggest another 24 to 45 inches of snowfall by New Years' morning.  The recent weather pattern has left the snowpack teetering near the edge of failure for days and the final round of heavy snowfall today and tomorrow will spur another natural avalanche cycle.  Obscured visibility day after day has prevented avalanche observations, but two recent avalanche observations, one from the south side of Mt. Crested Butte and the other from the Red Lady skin track clearly illustrate the very dangerous avalanche conditions.  Use the utmost care to avoid avalanche terrain and avalanche runout zones.  Avalanche activity may impact common winter travel corridors beyond winter trailheads such as Kebler Pass Road, Slate River Road, Gothic Road, Brush Creek Road, and Cement Creek Road.

With week-long snow totals matching or exceeding previous historical monster storms (think March 2019, January 2017, and March 2015), you should exercise more caution than usual (take a look at the graphic in the media gallery below to see how this storm compares).  Unusual weather often produces unusual avalanche activity.  The final round of snowfall to this unusual stormy period will steadily increase the avalanche hazard for the next 36 hours.  Expect a crescendo of avalanche activity to occur overnight and into Friday.  An EXTREME danger rating trend has been set for the Northwest Mountains on Friday to account for massive slab size and the potential for valley bottoms to be hit by very large, destructive avalanches.

Régions couvertes