Lawinenlagebericht

Southeast Mountains

Crested Butte Avalanche Center
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Lawinengefahr

Sun
Hochgebirge
2 · Mässig
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

The heatwave peaks this weekend.  Start and finish your tours early while the danger is lower and choose more conservative terrain as the day progresses.  Unusually warm temperatures will increase the threat of dangerous wet avalanches and cornice falls.  Stay off of steep terrain if you are sinking past your ankles into wet, mushy snow.  Dangerous avalanche conditions could develop this afternoon, particularly in the Southeast Mountains.  

Lawinenprobleme

  • Loose Wet

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

    In steep, sunbaked terrain, the threat of natural and triggered wet avalanches will increase as the snow becomes wet and slushy. The warm temperatures and the high sun angle will spread wet loose concerns around the compass to all but the highest, shadiest aspects.  Wet loose avalanches at higher elevations will be relatively small, some at lower elevations could gouge deep into the snowpack causing more destructive slides.   In isolated terrain, large wet slabs could release. Be especially careful above trees, cliffs, and gullies, or if you are sinking through bottomless wet snow.  Obvious signs of wet problems include rollerballs, pinwheels, or if you start sinking deep into a saturated snowpack. Move to colder aspects or lower-angle terrain when the snow gets hot and mushy. 

    4/2: Debris from a skier triggered wet loose avalanche that gouged into weak and wet snow.

  • Cornices

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2

    This week, cornice falls have produced a handful of large avalanches. Overhanging masses of snow can break under your feet further back than you might expect, or they can release naturally (ex. Whetstone, Emmons, and Owen). This is a difficult avalanche problem to predict, but they are more likely to topple during sustained warmups. Give these overhangs a large berth when traveling near them on ridges, and consider your exposure to overhead hazards below corniced terrain. 

    Recent Cornice Fall on Mt Owen. Photo: Dave Kozlowski

  • Persistent Slabs

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

    An isolated distribution of stubborn slabs over persistent weak layers several feet deep exist across high elevation aspects on the northern half of the compass.  Although avalanche activity has been infrequent, use caution on previously drifted, shady aspects where the snowpack is shallower than normal.  That's the type of terrain that most avalanches breaking into older snow have released on in the past few weeks.   Cornice falls have been the most common triggers for this problem recently, although there have also been several natural and human-triggered slides across the Central Mountains in recent weeks.  Some avalanche paths that ran in February are suspect because they hold shallower, weaker snowpacks.   Pay attention to the snowpack structure and assess the consequences of a rare but larger avalanche before riding steep terrain where the snowpack has remained mostly dry.  

    3/27: A natural persistent slab on Mt. Whetstone, triggered by wind loading.

Avalanche Discussion

Near or record high temperatures this weekend will accelerate melting and increase wet avalanche hazards.  This video sums it up well.  A handful of natural and skier-triggered wet loose avalanches ran yesterday, spanning the compass to all but due north aspects.  In terrain that has held a shallow, weak, and cold snowpack all season, wet loose avalanches have the potential to gouge through the entire snowpack and create larger debris piles. This setup is most common on below treeline, shadier aspects that are transitioning from dry to wet this weekend.  We've observed a string of large cornice falls this week. In some cases, cornices have triggered large slabs.  More intense warming will only exacerbate the issue.  Use extra caution below cornices this weekend: that means minimize or avoid spending time below corniced slopes.    

The threat of wet slabs is increasing. We have some uncertainty about how extensive wet slab activity will be today.  So far with this warmup, we have not seen indicators of wet slab releases.  However, this is the hottest day yet and the refreeze was worse last night.   We have well-developed weak layers lower in the snowpack capable of producing large wet slabs when and if water rapidly drains into them.  The most concerning slopes are those that held a mostly dry snowpack that are now seeing efficient melt-water for the first time.  I suspect that would be "shoulder aspects": westerly or easterly facing terrain, or perhaps high elevation slopes on the southern quadrant.  Whether or not we see wet slabs develop today, it is wise to travel suspiciously given the alarming temperature trends.  Move off of steep slopes before they are saturated and before you start sinking through the snow surface into wet, mushy snow.  Harvest the corn early in the day while the upper snowpack is still frozen or choose mellower terrain if you are roosting your snowmachine through wet mushy snow later in the day.    

Deeper and denser snowpacks will be more resilient to both the full depth wet loose gougers and the onset of wet slab activity.  Because the Southeast Mountains have more slopes with a shallower and weaker snowpack, we expect to see more large wet avalanche activity developing in that zone first.  Thus we are showing the rise to CONSIDERABLE danger in the Southeast Mountains for this afternoon, and expecting the Northwest Mountains to follow suit tomorrow after another night of weak refreeze. 

Are you still reading? You should be heading out the door by now, it's already warming up.    

 

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