Bollettino valanghe

Gunnison

Crested Butte Avalanche Center
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Pericolo valanghe

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Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

Following another weak refreeze, triggering a large wet avalanche remains a concern.  East aspects near and below treeline have been most active for wet slabs in the past two days.  Travel early and move to mellower terrain if the snowpack is saturated and not supporting your weight or if you see rollerballs and pinwheels occurring.   The threat of triggering a large persistent slab remains on high, northerly aspects, especially where the snowpack is variable in depth with previous wind drifting.  

Problemi valanghivi

  • Wet Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2.5

    Over the past two days, a handful of large wet slabs failed as buried weak layers became saturated.  This is a difficult problem to assess or predict.   Weak facets a couple of feet deep and depth hoar at the bottom of the snowpack are getting flooded for the first time this season on some easterly and westerly aspects.  Steep slopes below rocky terrain tend to be the most problematic.  Most northerly aspects have not received enough meltwater to be a problem, though terrain transitioning from E to NE and W to NW is a concern.  You can reduce your risk by traveling early while the upper snowpack is frozen and avoiding the most suspect terrain highlighted above.  

    A large, messy wet slab that ran yesterday on Gibson Ridge.  

  • Loose Wet

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

    Wet loose avalanches can be triggered where the upper few inches of snow become wet and mushy.  Most are relatively small, while some gain volume in longer terrain or gouge deeper into the snowpack and grow large and dangerous in size.  Wet avalanches are most likely to develop on easterly aspects this morning.  Increasing clouds and wind may prevent the problem from developing on higher terrain or on the western half of the compass later today.  Travel early and monitor the snow surface for over a few inches of thaw.   Pinwheels, rollerballs, and natural wet activity are signs of decreasing stability.   If this happens, move to lower angle slopes, smaller terrain, or colder aspects.  

    A wet loose avalanche that started below a steep rock band and gained volume in long, steep terrain.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    In the past two weeks, numerous large to very large slab avalanches broke on weak layers in the upper snowpack and near the ground.  Feedback on the problem is variable and infrequent. These issues are most concerning on wind-loaded terrain on northerly aspects.  Avoid steep, wind-loaded slopes and wind-affected terrain with variable snow depths to reduce your risk.   Persistent slab instabilities are more isolated below treeline; stay alert on very steep or unusually shallow slopes. The south half of the compass lacks the problem.

    A large persistent slab on Gothic triggered by a shallower wet avalanche on 3/25.

Avalanche Discussion

Wet avalanche problems are caught in a tug-of-war between the forces of evil (another weak refreeze overnight and a snowpack that is becoming saturated) and the forces of good (cooling temperatures, increasing cloud cover and winds today).  We expect a significant downturn in natural activity compared to the last few days, but human triggering a large wet avalanche remains a concern.  Meltwater finally reached our buried depth hoar layers yesterday, evidenced by several large wet slabs that broke near the ground on east aspects near and below treeline.   Some of these slabs were near the transition from E to NE aspects, so we expanded the wet slab rose due to concerns for the problem creeping into those shadier aspects, with a similar pattern expected on W to NW aspects.  Until the upper snowpack freezes hard, I'd remain cautious of that type of terrain.   Most southerly aspects have already transitioned beyond concern, and your primary hazard there is monitoring for any developing wet loose instabilities if clouds lose the tug of war with the sun.  On slopes where surface crusts break down, there will be potential for wet, loose avalanches to gouge deeply because the snowpack has become saturated in the past few days.     

Tomorrow, new snow problems will develop at upper elevations, particularly on wind-drifted slopes.  The new snow may also insulate our saturated snowpack and keep the threat of wet slabs lingering, especially at lower elevations.  The snowpack has remained mostly dry on high, northerly aspects, thus our persistent slab issues are still a low-likelihood threat on those higher, colder aspects.  

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