Bulletin d’avalanche

Southeast Mountains

Crested Butte Avalanche Center
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Danger d’avalanche

Fri
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Points saillants

The recent storm snow will start to shed naturally today on sunbaked slopes as the snow surface gets wet.   Move towards colder aspects or less consequential terrain to avoid getting pushed around by a wet loose avalanche.   On shaded aspects, it is possible to trigger soft slabs that break on weak layers in the upper snowpack, such as this skier triggered slab avalanche yesterday.  Both of these problems have the potential to be larger in size and more common in terrain that was favored by the last storm, further west and further east from the Crested Butte donut hole.   Pay attention to recent snow amounts and terrain consequences before considering avalanche terrain.  

Problèmes avalancheux

  • Loose Wet

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

    Natural and human-triggered wet avalanches will develop on steep, sun-baked terrain that saw more than about 6" of snow over the weekend.  Wet loose instabilities are easy to recognize and avoid:  If you see rollerballs, pinwheels, or small sluffs starting from rocky terrain features, move towards colder aspects or lower slope angles to avoid the problem.  While most wet avalanches will be small, they can cause trouble if they drag you into rocks, trees, or a gulley.    Expect wet avalanche activity to develop late morning on easterly aspects, and move around the compass to south then west aspects as the day progresses unless increasing cloud cover arrives first.    

    Small wet loose avalanche activity initiated by solar warming yesterday. Slides like these will become larger and more widespread under today's sunnier and warmer weather.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    A handful of recent skier and remotely-triggered soft slabs have failed on buried weak layers in the upper snowpack this week (Example A, Example B).   Avalanche activity has been most common on the northeast quadrant of the compass, where there are thin crusts surrounding facet layers paired with more favorable windloading from the last storm. You can also find isolated instabilities on the northwest quadrant of the compass.  The ingredients for an avalanche only exist on some slopes, but slabs are soft and shallow enough to be easily triggered if you do find the wrong slope.  You can get into trouble on a slope with enough recent or windblown snow to form a slab overlying facet or faceted crust layers below it.  Monitor potential slab thickness and terrain consequences as you move through steeper terrain, treating suspect aspects as guilty until snow assessments have proven them innocent.  

    3/17: A small skier triggered persistent slab that failed on weak layers formed during the dry spell in late February and early March.

Avalanche Discussion

Today marks the sunniest and warmest day since our weekend storm.  The recent snow will start to sluff off of steep, sunny terrain as it gets wet.  Areas that saw more snow over the weekend will see more action. We're showing a higher likelihood and larger potential size for wet loose activity in the Northwest Mountains today because that terrain generally picked up more snow from the last storm - up to about a foot of settled storm snow below treeline in the Anthracites and Ruby Range.  Wet loose concerns will be smaller and more isolated in the Southeast Mountains unless you are near the headwaters of the Cement or Brush Creek.  Some weather models are pointing towards clouds thickening this afternoon, which would temper wet loose activity. 

Skiers yesterday triggered a pair of soft slabs that broke on faceted layers that formed during our late February and early March dry spells.  Although these slides were shallow and relatively small in size, they demonstrated characteristics that are common with persistent slab behavior:  wide propagation and remote triggering.  The triggered slides yesterday were about 6" thick, on a northeast aspect of Wolverine Basin.  This fits the pattern of where we have seen most avalanche activity on our March weak layers.  Expect slides like this to be thicker in areas that saw more snowfall, again further west or further east of Crested Butte.  We have a new blog post that describes this new generation of persistent slabs - a very different beast than the persistent slabs that we saw back in February.    On that note, we haven't put the deep persistent weak layers to bed.  Although it has been several weeks since we have observed an avalanche breaking on deeply buried weak layers, yesterday an observer triggered a collapse and shooting crack that would have produced a deeply failing avalanche if it were on a steeper slope.  This is the first obvious sign of instability we've observed on deeper layers this month: a stark reminder that there are still a few land mines out there.  Our travel advice for those isolated concerns remains the same: seek out deeper, more uniform snowpacks and don't dilly dally below large cornices.  

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