Avalanche forecast

Tetons

Bridger-Teton Avalanche Center
View on map

Avalanche danger

Wed
Alpine
1 · Low
Treeline
1 · Low
Below
No rating
Open full map
Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Prolonged dry weather has caused a decrease in the likelihood of avalanches. Vigilance is always warranted in avalanche terrain, and there remains a remote chance of triggering a slide 1-3 feet deep, particularly on shady slopes.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    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. Read the discussion below for more information on pit propagation and lack of avalanche activity. 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. 

    Remember that the habits we practice at LOW danger will be those we slip into when conditions change.  Very steep terrain on the north half of the compass punctuated by rocks, trees, and cliff bands are the most likely places to find this problem. Any avalanche, even a small one, could result in serious injury due to rocks and trees lurking in most runouts. Common right now are loose snow "facet avalanches" that could knock a rider off their feet in steep terrain. 

    Upper elevation terrain that has been affected by the wind. Note the rocky, scoured slope to the left of the skier. Slopes like this contain shallow areas where humans could impact the weak layer.

Avalanche Discussion

When advising people on 7,000-odd square miles of (somewhat) snowy mountain terrain, you want to be sure you're not missing anything in the bigger picture. Messaging low danger with a persistent slab problem is tricky, just ask Colorado. So I did just that to discuss the current structure, the continued moderate to strong results in snowpit tests, and the lack of avalanche activity. 

The boxes we can check:

  • 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. The recent triggered slide in the Greys Zone illustrates the possibility of encountering instability given the current setup.  
  • Time without loading. Our last significant loading event was well over a week ago.
  • 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.  

The boxes we cannot check:

  • Physical signs of change. 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.
  •  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 to me, but brings me pause (and should bring you pause, too). 

The prolonged dry weather since early December has left us with a widespread weak, faceted snowpack. 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 turned sugary and cohesionless.  While the shifting weather pattern will open the door to instability, the forecasted snowfall over the coming week is not looking as promising as it once did. As usual in the business of avalanches, only time will tell.

Regions covered