Lawinenlagebericht

Northwest Mountains

Crested Butte Avalanche Center
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Lawinengefahr

Tue
Hochgebirge
4 · Gross
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

Up to two feet of snow and strong winds are a significant strain on the snowpack.  Natural avalanches are likely to continue on windloaded terrain today and dangerous conditions exist elsewhere.  Some avalanches could be very large and run long distances into low elevations.  Traveling in or below leeward avalanche terrain is not recommended today.  At lower elevations,  conservative terrain choices free of overhead hazards will help you enjoy the powder safely.    

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    2–3.5

    In the Northwest Mountains, we're expecting some avalanches to fail on buried weak layers today on windloaded slopes, producing large to very large avalanches.  The most prominent and active weak layer is buried surface hoar several feet deep on the north half of the compass. There is also smaller potential for avalanches to break on faceted crust layers on some higher, southerly aspects, or depth hoar layers near the ground.  Persistent slab avalanches can be remotely triggered from low-angle terrain and break larger and wider than you might expect.  Avalanches breaking into old weak layers are unlikely on low elevation, southerly aspects.  Slope angles consistently less than 30 degrees away from runout zones are a reliable way to avoid the problem.  

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2

    Nearly two feet of snow and strong winds are forming sensitive slabs, most commonly in wind-loaded terrain. Storm slabs are possible in wind-protected areas.  Slab avalanches breaking in the new and drifted snow have potential to step down and trigger larger persistent slabs.  Avoid traveling on windloaded slopes, where slabs will look and feel thicker.  In wind protected terrain, monitor for signs of instability such as cracking on small, steep terrain features to evaluate for new snow instabilities.  

Avalanche Discussion

It ain't over yet! We picked up more snow than expected overnight (about 6" to 8") and today's winds are also upgrading to strong speeds.  Poor visibility yesterday prohibited avalanche observations, but if there is an avalanche cycle happening, it's still going on today.   With snowfall expected to wind down this morning, the focus of natural activity will be on windloaded slopes.  Winds are ideal loading speeds in alpine terrain, and we have High danger painted across the alpine in both forecast areas. Near treeline slopes in the Southeast Mountains tend to drift more efficiently, and the snowpack structure is worse there, thus High danger also continues near treeline in the shallow zone.  

If snowfall tapers as expected, the threat of natural avalanches should significantly diminish below treeline today.  In wind protected terrain at lower elevations, you'll need to manage for overhead hazards as well as the threat of triggering avalanches in the new snow or much larger avalanches breaking on a surface hoar layer up to a few feet deep.  Conservative terrain choices are recommended given the significant loading period onto these buried weak layers.  Observations yesterday suggested that storm slabs were bonding fairly well to the dusty storm interface.  By traveling on southerly aspects below treeline, problems will be easier to manage.  You won't have to manage for deeper instabilities, and you can focus on shallower instabilities in the new or drifted snow.  

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