Bollettino valanghe

Snake River Range

Bridger-Teton Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Avalanche danger will start at Moderate and rise to Considerable. New snow and wind have built slabs less than 1 foot thick at middle and upper elevation terrain. These slabs will grow larger as snowfall and strong winds continue. The possibility of triggering a larger avalanche 2-3 feet deep remains in terrain above 8500'. Be conservative with decision-making around slopes steeper than 30°.

The NWS has issued a Winter Storm Warning that is in effect until Friday, 11:00 PM

Problemi valanghivi

  • Wind Slabs

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

    New snow and southwest wind overnight have formed slabs less than a foot thick in the middle and upper elevation on leeward aspects. These slabs will increase in size and sensitivity as an additional 5 inches of snow and moderate to strong winds are forecasted today. Carefully evaluate terrain where wind slabs typically form - ridgelines, cross-loaded gullies, and leeward slopes. The formation of drifts, fresh cornices, or blowing snow will give you an early indication of where wind slabs may be forming. Watch for obvious signs of instability such as shooting cracks, collapsing, and recent avalanches. Pay attention to rapidly changing conditions as the storm continues today. Seeking lower-angle or wind-sheltered terrain will help reduce your risk. 

    Additional Discussion: Temperatures above freezing may cause small wet avalanche activity at low elevations. Pay attention to - and stay out from under - very steep slopes where the new snow feels heavy or wet. Colder temperatures this afternoon will help reduce this problem. 

    (2/4/2025)

    A natural wind slab avalanche from the SE ridge of Smoky Hollow Peak. NE aspect 8800'. 

    Photo: Bridger-Teton Avalanche Center

  • Persistent Slabs

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

    Triggering a large avalanche big enough to bury you is possible on steep, rocky, convex, or wind-loaded slopes over 35° above 8500’. The 2-3 feet of snow that fell this week sits on a variety of weak layers that were covered on January 31st. This 1/31 weak layer is widespread and consists of facets and crusts. Avalanches failing on the 1/31 interface could travel far distances (including above you) due to the widespread distribution and continuous nature of the overlying slab. Managing this problem will be difficult because signs of instability, such as collapsing, cracking, or recent avalanches, may not be present. Due to the nature of the hard slab - slopes may appear stable. Multiple tracks on a slope are not necessarily an indication that it is safe – it might take one more rider to find the trigger point. Choose conservative and lower-angle terrain to manage the dangerous high-consequence avalanche conditions. 

    Weak snow near the base of the snowpack lurks 3-6 feet below the surface. The snowpack is continuing to adjust from the weight of the recent storm. Avalanches involving these layers could occur with a significant trigger, such as a large avalanche triggered at the 1/31 interface.

    (2/3/2025)

    A large skier triggered avalanche on a NE facing slope at 9,400' south of JHMR. It failed just above the new/old interface that was buried on 1/31. Seven skiers were caught and carried. All members of the party survived the incident.

    Photo: Bridger-Teton Avalanche Center

Avalanche Discussion

The latest storm is bringing an additional load of snow to our snowpack. Last night, 4 inches of snow fell at the Baird weather station. An additional 3 - 9 inches of new snow is forecasted to fall by 5 pm today with moderate to strong winds from the SW. This wide precipitation range creates uncertainty for the size and distribution of our wind slab problem today. We can confidently conclude that wind slabs will form based on snowfall totals and winds, but the large question mark is how large they will be. Should this storm produce on the upper end of expected precipitation, slabs may grow large and more sensitive. With this in mind, it will be important to pay close attention to changing conditions today. Many slopes will carry a higher level of uncertainty - due to this fact, using conservative decisions will help you avoid getting into trouble. 

The snowpack has gone through a lot of rapid change since Jan 31st causing unstable snow in the top portion of the snowpack. Before the recent storms, cold and dry conditions formed widespread weak layers of facets across many aspects and elevations. These weak layers are now buried by dense slabs and capable of producing destructive avalanches. Over 3” of snow water equivalent (weight of the snow) fell onto this weak interface – that’s a lot of weight, and the snowpack is still adjusting.

As we give the snowpack time to adjust, be conservative around avalanche terrain. It’s a good time to go back to an assessment mindset and start digging in the snow to see where the latest persistent weak layer (1/31) exists and if it is more likely to propagate a fracture (ECT and PST tests). 

Please continue to send in your observations, thanks!

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