Avalanche forecast

Tetons

Bridger-Teton Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

At elevations above 9,000', triggering a large avalanche remains likely on steep, wind loaded slopes. Many lower elevation areas also contain wind drifted slopes, as well as 1' to 2' thick slabs of storm snow that sit on top of weak snow. It is possible to trigger an avalanche large enough to bury a person on steep slopes even near valley bottoms. Evaluate the snowpack and terrain carefully for wind drifts, shooting cracks in the snow surface or sounds like whoompfing that indicate weak layers  in the snowpack. 

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Avalanche problems

  • Wind Slabs

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

    Thirty to forty inches of snow fell in the Tetons since Saturday. Since then,  winds howled from the southwest, west and north even at lower elevations. You are likely to find wind stiffened snow that may still be reactive to your weight in many wind-exposed locations and aspects. So far, challenging weather conditions have limited the number observations (and potential human-triggers) but a number D1-1.5 natural avalanches have been observed at lower elevations. Due to strong winds yesterday and continuing snowfall, these slabs may remain reactive today. Keep an eye out for shooting cracks, drifts and pillows. Remember that atypical wind directions, like the north wind yesterday, create wind slabs in unusual locations.

     

    (2/22/2023)

    Shooting cracks and whompfing were found on both supported and unsupported features. These clues to instability were supported by nearby moderate snow pit tests for propagation. Similar signs were found in the Tetons.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–3

    A significant slab has been added to locations that have held weak snow, particularly at lower elevations.  Avalanches were observed or triggered yesterday that indicate the sensitivity of buried weak layers. Triggering an avalanche will be most likely on weak snow recently buried within the top 1-3 feet of the snowpack. The drought condtions and cold clear nights prior to the most recent storm resulted in widespread near surface facet growth.  While not the weakest of weak snow grains, they are not to be trusted.  Perform stability tests near your intended line and consider terrain factors that could create problems like convexities, buried rocks or slope angles over 35 degrees.  

    Low-elevation slopes have very weak snow. Any slope steep enough to slide, regardless of elevation, should be assessed carefully. Conditions remain sensitive, especially in wind loaded areas where slabs are thickest. So far, upper elevation avalanches on the more deeply buried persistent layer (Jan 26th layer) have not been observed and it's possible that these locations with a much deeper snowpack over the buried weak layers will remain dormant.

    (2/21/2023)

    This natural avalanche occurred on Cache Creek Road and propagated a long distance due to well-developed weak snow. 

Avalanche Discussion

The recent storm delivered a strong dose of water weight (30-40" with 3-4" water) and along with it, another test to our snowpack. Today's forecast is supported by a fair number of direct observations that show that most avalanche activity above 9,000' was a result of wind loading and up to 4' in depth. Areas below that elevation saw widespread avalanche activity thgouh avalanches were smaller. Of course smaller is a relative term. Some of these were just large enough to bury a person and definitely large enough to carry someone into rocks, trees and terrain traps. So far, upper elevation avalanches on more deeply buried persistent layers have not been observed and it's possible that these locations with a much deeper snowpack over the buried weak layers will remain dormant. This dormancy seems unlikely in shallower areas at mid elevations and below that have received the first "test" with this snowfall. Keep the weak snow in areas with a thinner snowpack in mind as you venture out. 

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