Bollettino valanghe

Bitterroot

West Central Montana Avalanche Center
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Pericolo valanghe

Fri
Alta quota
4 · Forte
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Very dangerous avalanche conditions exist today. Large human triggered avalanches are very likely at middle and upper elevations due to significant new snow and wind. Stay off of and out from under steep slopes, especially where the wind has drifted fresh snow. 

Problemi valanghivi

  • Wind Slabs

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

    Large human triggered wind slab avalanches are very likely today. Over the last 24 hours, a significant storm delivered 8 to 12+ inches of new snow with strong shifting winds. Due to shifting wind directions, you will likely find wind slabs on all aspects at middle and upper elevations. Northeast winds today will drift the new snow onto atypical south and west aspects. 

    Wind slabs often appear smooth and rounded, but may be more difficult to identify today due to shifting wind directions. 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, which can cause a large destructive avalanche. Stick to slopes under 30 degrees in steepness today without steep slopes above. 

  • Persistent Slabs

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

    Large and potentially destructive persistent slab avalanches are likely 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. Over the last 24 hours, 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. 

    You can recognize persistent weak layers 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. You could remotely trigger avalanches from flat or gentle terrain above, below, or to the side of steeper slopes. Stay off of and out from under avalanche terrain today. 

    (1/13/2024)

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

Avalanche Discussion

After several days of cold but calm weather, a significant storm impacted the region yesterday into last night. Very dangerous avalanche conditions exist today. Large human triggered avalanches are very likely, and natural avalanches are possible. 

Last night’s storm delivered over 1” of snow water equivalent to all three forecast zones with strong west winds. The Central Bitterroot received the most snow, with 1.6” of SWE. This morning, an arctic front is moving across the region, bringing a wind shift to the northeast. There is plenty of new snow available for transport, so wind slabs will continue to build and shift today. 

Over the last week, we received reports of several significant persistent slab avalanches that occurred during last week’s storm cycle. They failed on a variety of buried weak layers. Last night’s storm added a significant load to the weak layers and likely brought them near their breaking point again. 

The best way to manage the hazard today is to avoid avalanche terrain. Be aware of the terrain above and around you, as you can trigger an avalanche from a distance (remote triggering). 

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 new 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!

Regioni coperte