Lawinenlagebericht

Bitterroot

West Central Montana Avalanche Center
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Lawinengefahr

Sat
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Kernpunkte

Large and potentially destructive human triggered avalanches are possible at middle and upper elevations today. You could trigger avalanches from flat or gentle terrain adjacent to steeper slopes. Look for red flags like cracking, collapsing, whumpfing, or recent avalanches. If you encounter these, stick to slopes under 30 degrees in slope angle without steep terrain above. 

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–2.5

    Large and potentially destructive persistent slab avalanches are possible today at middle and upper elevations. A variety of overlapping buried weak layers, including surface hoar, facets, crusts, and depth hoar exist on all aspects at upper elevations and north through east aspects at middle elevations. On Wednesday, a significant storm delivered over 1” of snow water equivalent to the region. This added a significant load to the buried weak layers, making them more sensitive. Yesterday, we received multiple reports of riders remotely triggering avalanches that failed on weak snow near the ground. 

    You can recognize persistent weak layers and poor snowpack structure by digging into the snowpack and looking for a dense slab on top of weak, sugary snow. Buried surface hoar can be more difficult to identify in a snowpit but often appears as a thin horizontal line across the snowpit wall face. 

    Red flags include whumpfing, collapsing, shooting cracks, and recent avalanches. Be aware of the terrain above and around you, as you can trigger an avalanche from a distance (remote triggering). If you find poor snowpack structure or signs of instability, stick to low angle slopes. 

    (1/13/2024)

    Large persistent slab avalanche on an upper elevation east facing slope in the Bitterroot. 

  • Wind Slabs

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

    Human triggered wind slab avalanches are possible at upper elevations today.  On Wednesday, a significant storm delivered 8 to 12 inches of new snow with moderate to strong shifting winds. Due to shifting wind directions, you could find wind slabs on all aspects at upper elevations. 

    Wind slabs often appear smooth and rounded. However, light snowfall today may conceal the wind slabs and make them difficult to identify. Expect to find wind-drifted snow just below ridgelines, and in cross-loaded gullies. 

    Signs of instability include shooting cracks, collapsing, and recent avalanches. Any wind slab also has the potential to step down onto deeper buried persistent weak layers and cause a large and destructive avalanche. The simplest way to manage the hazard is to avoid steep, wind loaded slopes, especially if you find signs of instability.

Avalanche Discussion

Yesterday, we received multiple reports of riders remotely triggering avalanches that failed on weak snow near the ground. One of these slides occurred in the Central Bitterroot and was 4 to 6 feet deep and around 300 feet wide. Wednesday’s storm added a significant load to the many weak layers buried in the snowpack. It brought them near their breaking point again. Avalanches failing on these weak layers have the potential to be very large and destructive, especially in areas with deeper snowpacks. 

Peak storm instability has passed, especially for wind slabs. However, persistent weak layers take time to heal, and triggering a persistent slab avalanche remains possible. Remain diligent and remember that persistent slab avalanches take time, patience, and self-control to manage. Pushing the boundaries and stepping out to steeper slopes can be tempting. It's essential to resist this urge and opt for low-angle skiing and riding while giving the snowpack time to strengthen. 

After a dry and cool day yesterday, today, we can expect light snowfall to accumulate 1 to 4 inches. Light winds will blow from the south, and there will be a warming trend into tomorrow. 

The snowpack at lower elevations is slowly building but remains thin. Continue to keep an eye out for ground hazards such as downed logs, stumps, and rocks. They may exist under recent snow and be obscured from view.

Let us know what you are seeing in the mountains by submitting an observation. Even just a photo or letting us know how much snow fell helps us greatly! 

Ski and ride safe!

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