Bollettino valanghe

Salt River and Wyoming Ranges

Bridger-Teton Avalanche Center
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Pericolo valanghe

Sun
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

Human triggered avalanches remain possible at all elevations today. Fresh wind slabs near ridgelines and start zones as well as avalanches failing on buried weak layers on the southern half of the compass are the primary concerns. The avalanche danger could rise to Considerable on steep slopes that receive direct sunlight and have been recently wind affected. Pay attention to cracking within wind drifted snow and monitor the effects of the sun today. 

There were two avalanche involvements this week involving burials, one of which was critical with a fatal outcome. You can find details here. Our sincere condolences go out to the friends and family for their loss.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–1.5

    Fresh wind slabs near ridgelines and start zones will be reactive to human triggering today. If triggered, soft slab avalanches up to size 1.5 will be likely in lee terrain with slope angles nearing 40 degrees. Old stubborn wind slabs from the February 19-23 storm cycle exist in the alpine in isoloated areas. 

    Pay attention to signs of instability such as cracking within wind drifted snow and monitor slope angles. 

    Dry Loose: Dry loose avalanches are a concern in very steep, rocky, sunlit terrain today. Monitor the effects of the sun today.

  • Persistent Slabs

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

    Stubborn slabs that are both soft and hard could be triggered by humans today in specific locations. Slopes in excess of 35 degrees on the southern half of the compass are the most suspect, especially near rocky outcroppings and unsupported terrain features. 

    Weak faceted snow and slick crusts exist at both the Feb 18 and Jan 26 interface.  The Feb 18 crust/facet combo is buried 30-60 cm below the surface of the snow on West through South through East aspects at the middle and upper elevations. The Jan 26 crust/facet combo is buried 60-90 cm below the surface of the snow on southerly aspects. Triggering avalanches from a distance (remote triggering) is possible. 

    Pay attention to signs of instability such as audible collapsing of the snowpack and monitor the effects of the sun on the snow surface today. Your best line of defense against a persistent slab problem is to dig a snowpit in a representative location and perform some stability tests such as an Extended Column Test. 

     

Avalanche Discussion

Recent avalanches have been observed at all elevation bands, with failure planes either within the new snow or at the new/old interface. However, avalanches that have failed on deeper persistent weak layers have also been observed in some locations at the middle and lower elevation bands. This includes the fatal incident that occured on the Jan 26 layer in the Greys River Zone on Thursday. Wind slabs are present on a variety of aspects and elevations but mostly confined to alpine zone in the lee of WSW winds. 

The snowpack structure varies throughout the Greys River Zone. The Palisades, Salts, and Snake River core have depths and structure that is akin to that of the Tetons (think deeper, stronger). As you move south and east towards the Wyoming range snow depths become more shallow, and the effect from arctic air masses more pronounced (similar to Togwotee). A great deal of uncertainty revolves around the structure and stabilty of the more remote areas within the Wyoming range due to a lack of observations. 

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