Bollettino valanghe

Tetons

Bridger-Teton Avalanche Center
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Pericolo valanghe

Thu
Alta quota
1 · Debole
Limite del bosco
1 · Debole
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

Prolonged dry weather has caused a decrease in the likelihood of avalanches. Take advantage of conditions, but factor in low coverage and remember vigilance is always necessary in avalanche terrain. A dose of bad luck could trigger a slide 1-3 feet deep, particularly on shady slopes. 

Problemi valanghivi

  • Persistent Slabs

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

    Weak snow is buried 1-3 feet deep on most shady middle and upper-elevation slopes. Field observations find unstable conditions in snowpits, with propagation continuing several days after any new snowfall. On 12/30, a snowmobile-triggered avalanche was reported near Gunsight Pass in the Greys River forecast zone. This event illustrates the possibility of unstable snow on isolated features and highlights the need to remain vigilant during periods of low danger. 

    With each day of dry weather, the snow surface grows weaker. On most slopes that aren't steep enough or due solar and haven't been cooked by the sun, the top ~8 inches of the snowpack have faceted and are cohesionless.  These loose snow "facet avalanches" are relatively harmless unless you get knocked over by your sluff in high-consequence terrain. Any avalanche, even a small one, could result in serious injury due to rocks and trees lurking in most runouts. 

    (1/3/2024)

    Despite an absence of avalanche activity, pit results still show moderate to high strength and propagation. With a dose of bad luck, you could find terrain that harbors unstable snow and a slab capable of producing an avalanche.

    Photo: Gabrielle Antonioli

Avalanche Discussion

A Tom Robbins quote comes to mind: "Don't confuse symmetry with balance."

Now is a good time to adventure in the mountains and take advantage of unusually safe mid-winter avalanche conditions. Bear in mind that these conditions are the product of dry weather alone and not an improving or stabilizing snowpack for the season. Our habits follow us. Things will become more dangerous when the storm track returns, likely by this weekend.  In the meantime, have fun and keep it tight!

SOME GOOD

  • No obvious signs of instability. If you experience cracking or collapsing—do not pass GO! But it's been several weeks since reports of these signs in avalanche terrain have come in. Given the current setup, the recent triggered slide in the Greys Zone illustrates the possibility of encountering instability.  
  • Time without loading. Our last significant loading event was well over a week ago. Less snow usually equals fewer avalanches. 
  • Periods of temps near freezing. And not because they are healing anything, but rather because it is preferable to see if a weak layer can withstand a few days of warmer temps.  

SOME BAD

  • No physical signs of change in a thick weak layer. The best way to heal a weak layer is to compact it beneath a heavy snow slab. But even where 12/1 has been buried by a heftier slab, the physical properties of this weak layer have looked the same, remaining relatively thick and dry and propagating cleanly in tests.
  •  No improving snowpack test scores. Pits are great at telling us when things are unstable but not so good at predicting overall stability.  This category remains inconclusive and brings me pause (and should bring you pause, too). 

 

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