Bulletin d’avalanche

Gunnison

Crested Butte Avalanche Center
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Danger d’avalanche

Thu
Alpin
2 · Modéré
Limite forestière
1 · Faible
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Extreme winds over the past 24 hours have blasted snow into Kansas, into the stratosphere, and in some cases, into thin drifted slabs in leeward terrain features.   Use caution in consequential terrain where you find signs of wind-loaded snow.  Drifts will have a chalky and dense feel to them compared to surrounding crusts or rippled eroded snow.    Although it's unlikely, we have lingering concerns that you can trigger a larger slab avalanche that breaks deeper into the snowpack on northerly facing aspects in very steep, rocky, or unsupported terrain.  

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    Strong to extreme winds since Monday night have been actively blowing snow at all elevations, especially above treeline.  In many cases, it appears that winds were too strong to effectively load typical leeward slopes.  However, in some catchments such as gullies or concave features, you may find drifts that are stiff enough to knock you off your feet and take you for a ride.   Wind slabs will look and feel different than eroded or protected snow surfaces.  They'll have a chalky, pillowy appearance that might differ in color tone.  Drifted snow will feel thicker and denser than adjacent crusts or eroded snow surfaces.   Because winds were unusually strong, you may find slabs lurking further down slope than normal or in unusual locations.  Use extra caution above cliffs, gullies, or trees, where the consequences of a small slab will be magnified.  

    4/5: Blowing snow off of the summit of Mt. Whetstone, caused by strong westerly winds.  

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    1.5–2

     Slab avalanches breaking into old weak layers several feet deep have become unlikely, but not impossible.  Higher elevation, northerly facing terrain still holds a dry, winterlike snowpack; thus we can't completely eliminate the potential for a rare but large slab avalanche on these aspects.  The most suspect terrain is convex or unsupported slopes, especially near rock bands. You are most likely to trigger a slide from a shallower spot on the slope.  If you are skiing or riding in that type of terrain, reduce your group's exposure during uphill travel and choose appropriate safe zones from a large avalanche while descending.  Let your friend wrestle their stuck snowmobile off of suspect slopes by themselves.  

    Example of a persistent slab avalanche that likely failed last week.  The avalanche highlights the type of terrain that is most worrisome:  northerly, rocky, and unsupported.  

Avalanche Discussion

The mega-wind event steals the headlines.  All of our wind stations recorded extreme gusts yesterday, ranging from 70 to 80 mph in the alpine, to 40 to 50 mph at mid and low elevations.  Observers yesterday reported blowing snow, snapping trees, and small airborne pets.  As is often the case with these extreme wind events, wind slab formation appears to be small and fairly isolated because winds were too strong for effective loading.  Of course, there's some forecaster uncertainty following an unusual wind event, especially above treeline, where we saw extensive blowing snow off of the peaks and had limited travel or visibility yesterday.  Winds are shifting from the west to northwest and may find more transportable snow to work with today.   Fortunately, wind slabs should be fairly easy to recognize and avoid in your travels.  Their chalky texture will contrast sharply against the melt-freeze crusts that blanketed all but northerly aspects prior to the wind event.  On northerly slopes, loaded slabs will look smoother than eroded sastrugi ripples.  

Mostly stable test results over the past few weeks and only a couple of persistent slab avalanches since Mid-March  (Example A, Example B) highlight that our buried weak layers are becoming increasingly less of a concern within our forecast area.  East to south to west aspects have transitioned to a strong spring snowpack, while northerly aspects give us enough uncertainty that we continue to list the problem.  This fresh persistent slab from the Continental Divide between Aspen and Leadville exemplifies what the problem looks like.  

End of season party! Join us at the Talk of the Town Friday, April 8 from 6-10 p.m. as we wish to say thank you to all of our sponsors, supporters, and the community at large. We will have complimentary Modelo beer for everyone, live music from Congo Turner & Company, and a free raffle.

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