Bollettino valanghe

Gunnison

Crested Butte Avalanche Center
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Pericolo valanghe

Tue
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1 · Debole
Limite del bosco
2 · Moderato
Sotto il limite
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In sintesi

A taste of spring!  Stay alert for point-release avalanches in high-consequence terrain as the snow surface gets damp or wet on sunbaked slopes. Old drifted slabs remain an isolated concern: choosing softer wind-eroded, or wind-sheltered snow can help keep you from lingering slab concerns.  Both of these issues are most problematic in consequential terrain above trees, gullies, or cliffs.  

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    You can trigger wet avalanches as the upper snowpack moistens or gets wet on sunbaked slopes.  Some of these may gouge deeper or grow larger than expected because of how weak and unconsolidated the existing snowpack is in wind-sheltered terrain - it's a wetter, heavier version of our facet sluff problem from the past few weeks.  Wet loose avalanches will be most dangerous in high-consequence terrain above cliffs, trees, or gullies. If snow surfaces produce rollerballs, pinwheels, or natural sluffs, move to less consequential terrain. You can avoid the problem on slope angles less than 35 degrees or colder aspects where the snow surface is frozen.  

    An example of a small wet loose avalanche and rollerballs from last spring.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    1–2

    Slabs up to several feet thick are becoming increasingly isolated and difficult to trigger but remain a concern on a few previously wind-drifted slopes.  You are unlikely to see signs of instability before triggering an avalanche that breaks on old weak layers.  The most concerning terrain features are where old, drifted slabs are thin near their margins, convexities, or rocky areas. You can reliably avoid the problem on slope angles less than 30 degrees without steeper slopes above you, and wind-protected terrain generally lacks the problem.  

    This avalanche was triggered by a backcountry rider on 1/26 outside our forecast area near Ashcroft. This is a good illustration of the wind forming a slab below a midslope roll. 

    Photo courtesy CAIC. 

Avalanche Discussion

Under unusually warm temperatures and sunny skies, the snowpack will get a taste of spring on the southern half of the compass.  This may spur some natural or triggered wet activity. Observers yesterday reported a warming snow surface and facet sluffs starting to get damp thanks to warm temperatures and an ideal greenhouse effect (ex. A, ex. B).  The most concerning slopes for wet loose avalanches have weak, unconsolidated facets that are now getting wet under strong solar, specifically east aspects this morning or west aspects this afternoon.  Low-elevation southerlies have seen numerous melt-freeze cycles this season and should be more resilient to the heat, and the absence of greenhouse clouds should keep northerlies frozen today. Either way, use simple spring travel tactics to manage for wet avalanches: If you see rollerballs, pinwheels, or sink past your ankles through wet snow, be cautious in steeper terrain.   Yesterday's greenhouse weather stiffened the snow surface enough to put a lid on most dry facet sluffs now.   If you climb above 11,000' and encounter a weak and sugary snow surface, stay alert for the problem.  

We're in an odd transition of a shallow and cold snowpack intersecting with the early arrival of spring weather.  In the springtime, we often head towards higher or colder aspects to avoid wet problems.  This strategy works today, but remember there is still isolated potential to encounter a hard slab in previously drifted terrain.  There were several human-triggered wind slabs and an explosive-triggered persistent slab last week.  Eric's observation from Cement Creek illustrates the types of slopes (smooth, rounded, drifted) where you might still find trouble. Our most recent winds have shifted to the southwest, with up to 2" of new snow to drift into leeward features. That's not much, but enough to form a few thin but sensitive wind slabs in favored terrain.  If you're riding in alpine terrain where you can't afford to get pushed off your feet by a small slab, you should also monitor for fresh drifts.  

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