Bollettino valanghe

Tetons

Bridger-Teton Avalanche Center
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Pericolo valanghe

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

In sintesi

Two feet of snow over the last three days sitting on a poor crust interface combined with shifting wind speed and direction will create reactive slabs on specific slopes exposed to the wind. The possibility also exists to trigger a larger avalanche on buried weak layers. Conservative terrain choice is warranted due to the unpredictable nature of buried weak layers experiencing rapidly changing conditions.

 

Problemi valanghivi

  • Wind Slabs

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

    The Tetons have received upwards of 24 inches of new snow in the last three days favoring the west side yesterday with 16 inches. Winds during this storm started off strong (20-30 mph) out of the SW transitioning N/NW and decreasing today. Wind slabs will be found primarily above 8500’ today in specific areas such as ridgelines, below cliff bands, and leeward terrain exposed to wind on NE-E-SE aspects. These slabs have been reactive to triggering due to poor bonding interface on a fairly widespread and concerning crust layer (see observation on Twin Slides). Slab depths will be 2-3 feet with the deepest pockets possible on isolated features in the form of large pillows. Be aware that shifting wind direction will change loading patterns. Always look for obvious signs of instability such as cracking. 

    In addition, pay attention to recent storm snow in areas with higher amounts of new snow if it begins to slab up. As a result you’ll see increased reactivity on the crust interface even in sheltered terrain. 

    (12/7/2023)

    D1 avalanche at the top of Twin Slides triggered remotely on a wind loaded pocket that propagated 30 feet wide and ran 400 feet. 9700' S aspect

    Photo: Alex Drinkard

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2.5

    We’ve got a complicated early season snowpack setting up. Weak layers now buried around 3 feet have experienced an active avalanche cycle over the last week that is slowly trending towards decreased reactivity. Even with decreased reactivity, it is still possible to trigger these weak layers. The highest likelihood will be where a stout crust below recent snow does not exist. This will be on northerly half of the compass above 9500’. Additionally, recent loading of new snow will add stress to these weak layers. Triggering a wind slab will increase the possibility of stepping down and creating a large to very large avalanche. Due to the uncertainty of these layers, cautious route-finding to avoid steep terrain is advised as the snowpack adjusts to recent loading and large temperature fluctuations.

     

    (12/5/2023)

    D2.5 Remotely triggered on Teton Pass that failed at persistent weak layer. 

    Photo: Travis Baldwin

Avalanche Discussion

Snowpack complications continue...

I want you to focus on those problems above thoroughly. Don’t try to out trick those problems today. There’s been a lot of new snow recently and a tricky early season snowpack. Wind slabs should be fairly straight forward to distinguish if you observe the snow surface and hardness changes of new snow carefully. The uncertainty lies on the poor interface with the slick crust formed during rapid warming on the 5th and 6th. The continuity and character of this crust makes the hair on the back of my neck stick up. So far new snow is bonding decently with the lack of firm slab quality. Cold temperatures today should preserve the new snow. The persistent slab problem is much trickier to identify. Northerly aspects above 9500’ without the new to old crust interface is the prime suspect to uncover this problem. And nobody likes getting in trouble. We can't count out the possibility of triggering those buried weak layers even where the crust exists.  There was a crust present on the avalanche triggered remotely at the Top of Triple Direct. Don’t be scared though, there’s plenty of good deep powder riding in sheltered terrain. I'll be avoiding those steep consequential slopes until I know more.

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