Bulletin d’avalanche

Salt River and Wyoming Ranges

Bridger-Teton Avalanche Center
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Danger d’avalanche

Mon
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 3 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Human triggered avalanches will be likely at the middle and upper elevations, especially where wind affected snow overlies buried weak layers and crusts. Areas of the forecast zone with shallower snowpacks such as the Wyoming Range harbor weak snow deep within the snowpack. Pay attention to signs of instability such as cracking within wind drifted snow and use your shovel to assess buried weak layers. 

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Wind slabs: Soft wind slabs that are 1-2 feet thick will be sensitive to human triggering at the middle and upper elevations. Winds averaged out of the WSW and will veer to the W today. 

    Storm slabs: Soft storm slabs up to 1 foot in depth could be lingering in sheltered terrain at the middle and lower elevations. 

    Dry Loose: Dry loose avalanches could pose a threat in steep terrain. 

    The failure plane for all new snow problems will likely be the most recent crust that was buried on 3/30.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1.5–2.5

    The March 20th interface is now buried 2-3 feet below above a stout slab. Active loading of new snow with heavy wind transport will add stress and increase the chance of triggering a large avalanche. This layer is composed of facets/crusts on solar aspects and small preserved facets on northerly aspects protected by the sun. The sensitivity and distribution of this layer is hard to gauge due to the varying slab depths, recent temperature fluctuations, and differing characteristics across slope aspects. Remote triggering could occur from gentler slopes above, below, or adjacent to steep slopes. Wind loaded terrain will have the highest likelihood of finding reactivity. Long story short: persistent slab avalanches are unpredictable, so careful snowpack evaluation is required. 

    In areas with a weaker snowpack, such as the southern portion of the Wyoming Range, deeper weak layers still remain a concern. Triggering a wind slab or persistent slab on the March 20th interface could step down to these layers resulting in a large to very large avalanche. 

    (3/28/2023)

    The third rider near or on slope triggered 1' thick soft slab from the diagonal track on the right. The slab slid on a slick crust with small facets on it that was buried March 20.

    Photo: Frank Carus

Avalanche Discussion

The Greys River Zone has picked up 6-10 inches of snow over the last 24 hours. Winds have averaged out of the WSW in the 15-25 mph range on the ridgelines. Current temperatures are in the mid 20s in the valleys and near 10 degrees on the peaks. 

The Greys River zone is composed of multiple mountain ranges with variable snow depths and snow layering. Snow climates are generally split up into 3 different groups: Maritime (coastal), intermountain, and continental. The ranges within the Greys River Zone exhibit characteristics of all 3 at times but generally span the continuous spectrum from intermountain to continental. 

Ranges on the eastern edge of the Greys Zone such as the Wyoming Range trend towards the continental end of the spectrum. This is due to lower snowfall totals in the lee of the other ranges and the increased exposure to cold continental air masses. As artic air moves south out of Canada it usually slides down along the continental divide (the spine of the Wind Rivers) but it can spill over South Pass and affect the SE corner of the Greys Zone. 

Ranges on the western edge of the Greys Zone such as the Palisades and Salt River Ranges trend towards the intermountain end of the spectrum. This is due to higher snowfall totals on the windward side of the ranges (though maybe not as high as some of the interior ranges) and less exposure to artic air masses. 

Régions couvertes