Bollettino valanghe

Tetons

Bridger-Teton Avalanche Center
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Pericolo valanghe

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

In sintesi

Triggering an avalanche large enough to bury a person is likely in steep, wind loaded terrain above 8,500', especially at ridgetops. Evaluate snow for cracking where you see wind sculpted pillows and drifts.  A few inches of new snow overnight obscured these clues of wind slabs that developed yesterday so you'll need to dig. Periods of sunshine today could make triggering easier.

Problemi valanghivi

  • Wind Slabs

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

    The month of March roared in like a lion with 66" of new snow falling since March 1st. 12-18" of that fell in the Tetons on  Tuesday night and early Wednesday. Southwest and west winds over the past three days periodically built wind slabs and cornices and did so very actively through the afternoon yesterday. South-southwest wind speeds gusted to 69 mph late last night. Yesterday morning, JHMR snow safety reported slab depths averaging 1-2' thick and a few up to 3-4' deep during mitigation. Human triggering and minor natural activity were also observed in the backcountry north and south of the resort and near Ski Lake. As mentioned above, signs of wind affect will be less obvious today due to the 3" of new snow that fell overnight. Partly cloudy skies and wind protected many areas from the destabilizing effect of sunshine yesterday.

    Skies will clear today with light wind so beware of sun on the snow. Steep, rocky couloirs facing the sun could grow wet and slide more easily. Snow depths at lower elevations have grown substantially in the past week. Natural small, wet avalanches are possible today on sunny buttes and steep rocky areas.

     

     

    (3/5/2024) Wind slab at 9500', SW aspect, 33 degree slope, trees of First Turn at Teton Pass. This observation shows slabs breaking easily yesterday afternoon even before the bulk of the new snow arrived overnight. Photo: Tianse Abeles-Allison

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    As stated yesterday, very large avalanches involving deeply buried layers of weak snow remain a possibility when we receive a large load of snow. True they are few and far between but when they break, they break big. At the risk of sounding like a broken record, very steep, hanging snowfields above cliffs along with rocky or notably shallow slopes are where you're most likely to find this problem. The avalanche pictured here is an example of this deep, but stubborn type of avalanche that occurred towards the end of the storm Tuesday night. 

    A weak layer of snow buried in January currently sits 3-5+ feet beneath a firm slab, depending on elevation. The shallow but growing snowpack at lower elevations makes triggering some depth hoar or this January weak layer possible at this point.   A large wind slab release or cornice fall also has the potential to trigger a very large natural avalanche such as this one on Treasure Mountain. 

    (3/6/2024) Crown of a very large (D3) avalanche in the South Fork Teton Canyon. This slide was triggered by a cornice fall on the right side of the photo. The avalanche occurred in steep, rocky NE-facing terrain at 9400' and ran 2400' to the valley floor and broke many mature trees.

    Photo: Cameron Galt

Avalanche Discussion

The copious amounts of snow that have fallen in the past week appear to be settling and bonding pretty well in most locations leaving us with mostly human-triggered avalanche problems today. The buried weak layer from January 4 reared its head during this storm in the Tetons and maybe elsewhere but appears dormant without a very large trigger. Only time and continued observations from forecasters but especially from the public will help us gain a better understanding of how deeply this layer is sleeping.  The persistent slab problem slider remains at possible due to the almost unlikely potential of a fresh cornice drop triggering this slab. All aspects of the upper elevation band are highlighted for wind slabs. You'll find lots of scouring on the southwesterly aspects but sunshine could make slabs or cornices on these aspects more sensitive to triggering.

If it seems like it's been snowing a lot, it has. Historical snowpack data shows that we surpassed snow depths at this time last year by five inches and the year prior by 49". You can find archived forecasts, snowpack summaries, and weather records here. (These pages are best viewed on a computer rather than a mobile device.)

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