Avalanche forecast

Tetons

Bridger-Teton Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Avalanche conditions remain dangerous. Make your terrain selection accordingly and be alert to the consequences of being caught in a slide where you are traveling. The recent storm formed sensitive wind drifts and added weight to weak layers buried in the snowpack. Reduce your risk by sticking to gentler slopes sheltered from the wind.  

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Yesterday brought a buffet of wind in the upper elevations from multiple directions. Fresh wind slabs will continue to form with moderate winds from the south/southeast at ridgetops, shifting to the northwest into the tail end of today. Yesterday we found sensitive wind slabs and upside-down snow (harder snow on lighter snow). Other folks skiing sheltered terrain on the west side found protected conditions and right-side-up snow (lighter snow on harder snow). The middle elevations were definitely touched by winds yesterday, and though speeds will taper today, the primary problem will remain the movement of recent and continued storm snow.

    As new snow settles or is worked further by the wind, slabs can become stiffer and sometimes the above problem can be worse days after a storm. This is worth bearing in mind as the weather clears briefly tomorrow. Slab depths will range from1-3+ feet, dependent on your elevation, and may break on mid-storm interfaces but also hold a higher possibility of breaking on layers deeper in the snowpack.  

     

    (2/28/2023)

    A rider found sensitive soft slabs, particular on lee aspects around 9,000'.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    We've got a complex snowpack stacking up and it's worth dissecting this problem rose because there's also plenty of safe riding to be found on the above aspects and elevations. It is more about your assessment and personal process of elimination with evidence of this problem, as well as locations you frequent.

    The Teton zone illustrates a wide range of conditions across elevations currently, as well as between the east and west sides.  A layer of facets, buried on Feb. 18th, remains particularly suspect, as incremental loading continues to occur throughout this week and into the next.  Numerous soft and hard slab avalanches have been triggered recently on this weak layer, now buried 2-3 feet (and counting) across all elevations and most aspects. Luckily, it's still fairly high enough in the snowpack that one can assess its presence by digging a pit, and is a crust+facet sandwich found on the southern half of the compass across most elevations, E-S-W. Weak snow is also present on the northern half of the compass, but I don't think the above layer will survive long as it continues to be buried deeper and lacks a crust to "preserve" it. For now, the process of elimination rules it out. On a NE aspect ~10,000 feet in the Tetons, Feb. 18th was nowhere to be found. However, we also triggered an avalanche from our pit location within the new snow, so keep your eyes peeled for the primary problem above on northerly aspects. 

    Recent activity on this layer: (Wolf Trap, No Name Canyon, Nugget).

     

    (2/26/2023)

    Crown an explosive-triggered avalanche at Targhee which failed on a crust facet combo.

    Photo: Dan Nagy

Avalanche Discussion

Remember back to the first half of the winter when we had one primary facet layer, and we knew that each loading event would likely produce large avalanches and dangerous conditions? Sigh...those were the days: dangerous, but simple and predictable. But the times are a-changin'.  Our snowpack isn't as hair-trigger, and unfortunately, has become more complex and a much less predictable animal. Even though we've seen a very snowy February, brief intervals earlier in the month between storms crafted some new weak layers. The higher sun angle of late winter has easily formed crusts, brief periods of clear and cold weather have created near-surface facets, and we've even had a few high-elevation rain events in the northern portion of the Greys River.

As we move towards spring, these fast-forming weak layers usually heal quickly.  But this steady trickle of light to moderate loading continues to keep some weak layers on edge, and we appear to be heading towards a colder and snowier spring. There have been enough natural and triggered avalanches to know that several weak layers remain in play. Realizing that snowpack conditions are exceedingly complex can be relieving in a way. It requires a shift in our approach to the problem—we can simplify the situation by going back to the basics. New snow + wind + weak layers + recent avalanches = dangerous conditions. Luckily we also have plenty of tools at our disposal to combat the aforementioned hazard equation. We can read a forecast and hopefully gather some useful information, look for evidence of the problems in the field, assess and reassess as winds or weather change, and ride plenty of fun snow this week. 

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