Lawinenlagebericht

Southeast Mountains

Crested Butte Avalanche Center
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Lawinengefahr

Sun
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist 3 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Friday's storm deposited about 6 to 11 inches of snow on average and created a small wind slab avalanche problem. The bigger persistent slab avalanche problem remains the greatest concern with the potential for avalanches to break 1 to 3 feet deep into old snow. The riding quality is great, even on lower-angled slopes. Consider using the terrain to your advantage to manage these avalanche problems, such as riding lower-angled slopes or smaller terrain features with lower pointal consequences. 

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–2

    Slabs 1 to 3 feet thick exist above persistent weak layers buried at the bottom of the snowpack. Recently this avalanche problem has become less sensitive to human triggering. The accumulating new snow will add load and potentially make this avalanche problem more reactive again. The most concerning aspects are northerly and easterly-facing slopes where we have recorded the majority of avalanche activity. The potential for triggered avalanches exists in other aspects but will be less commonly encountered.  Avalanches have the potential to break wider than you expect, and they can be triggered from flat slopes connected to steeper terrain. Consider the consequences of a large avalanche in the terrain you want to ride; smaller terrain features can lower the consequence if you do trigger an avalanche. While lower slope angles, without overhead hazards, can lower the chance of triggering an avalanche. 

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–1.5

    In some areas, recent westerly to northwesterly winds will have created small wind slabs on the lee sides of ridgelines and cross-loaded terrain features. Your eye may be clued into this potential avalanche problem by looking for thicker drifts or lens-shaped snow deposits. While this avalanche problem is generally small, a triggered avalanche could be enough to wake up the deeper persistent slab avalanche problem where the two overlap. 

    In this example photo, previous winds moved the snow from right to left and formed a wind slab avalanche problem were you can identify the thicker-looking drifts. 

Avalanche Discussion

Let's look at some storm totals from Thursday evening through this morning. The snow water equivalent (SWE) is the easiest to compare, as the actual snow height measurements are a bit variable with snowpack settlement not capturing all the pulses of snow we saw. Starting with SWE totals. Schofield Pass: .9" SWE. Irwin: 1.1" SWE. Gothic: .58" SWE.  Butte Snotel: .6" SWE. . Total snowfall in the NW Mountains between Irwin and the Upper Slate is between 8" and 12". Snow totals in the SE Mountains between Crested Butte and CBMR are between about 6" and 11". 

Alpine wind stations recorded periods of both light winds, and multi-hour periods with westerly to northwesterly winds averaging in the 20 mph range with gusts into the 30's and 40's from the west and northwest. 

This storm has added another small load to the persistent slab avalanche problem. In wind-protected areas, there will likely not be enough load to notably change the sensitivity of this avalanche problem, while wind-loaded areas will be more concerning. In the big picture, we are observing this avalanche problem trending towards more of an isolated/reactive distribution. In shallow snowpack areas, the slab is becoming weak and not propagating collapses, while in deeper snowpack areas the weak layers are slowly adjusting to the load and becoming more stubborn to trigger. The Goldilocks slopes still exist, where the problem is reactive and ready to be human-triggered. This patchwork of reactive vs stubborn vs unreactive isn't easy to manage and conservative terrain choices are one way to begin managing the uncertainty. Put your hand at your thigh or hip and imagine what a 1 to 4-foot-deep slab would look like in consequential terrain. 

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