Avalanche forecast

Tetons

Bridger-Teton Avalanche Center
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Avalanche danger

Sun
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Increased westerly wind over the last 48 hours continuing today will form wind drifted slabs on leeward and cross-loaded upper elevation terrain. Look for signs of wind drifted snow such as stiffened surfaces, large pillows, and cracking. Choose appropriate terrain as we still have persistent weak layers that could be triggered on thin, rocky, and previously wind affected slopes.

Avalanche problems

  • Wind Slabs

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

    Wind drifted snow has formed soft slabs less than a foot deep over the last 48 hours. Increased wind speed over 20mph of varying direction (WSW-WNW) has loaded leeward and cross-loaded slopes where you can find unstable snow in the upper elevations. Stay alert in alpine terrain especially above the forecast area of 10,500’. Wind slabs may be deeper on isolated terrain as seen in Upper Rock Springs yesterday. 

    Cornice Falls: Wind throughout the winter has formed cornices on N-NE-E-SE-S aspects in the upper elevations. Give cornices a wide margin of safety and be careful along ridgelines as they can break further back than expected. 

    (2/23/2024)

    Wind slab avalanche triggered outside of JHMR in the backcountry at 9700' NE aspect. 

  • Persistent Slabs

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

    Weak layers are persisting in the snowpack beneath hard slabs 3-5 feet deep above 7500’ primarily on the north half of the compass. These layers are trending dormant and there are a lot of slopes where you can avoid this problem. Triggering an avalanche is most likely on steep slopes with a shallow snowpack where the overlying slab is thin and riders can impact these weak layers. 

    • The most obvious slopes will be rocky and previously wind affected terrain where thin trigger points exist. 
    • Gain more knowledge of a given slope by probing for snow depths before committing to consequential slopes. Feel for hard snow above weak snow. The weaker layer will be closer to the surface in shallower areas. 
    • Large triggers such as recent cornice falls indicate that these weak layers can still be reactive (see observation from Mary’s Nipple).

    (2/17/2024) Photo: Teton County SAR

    The avalanche on No Name peak is a reminder of the destructive power of an avalanche failing on a deeper weak layer. This one required a very large trigger - either a cornice fall or possibly a smaller avalanche. Steep, rocky terrain like this is a breeding ground for this type of avalanche.

  • Loose Wet

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

    Warm temperatures combined with clear skies will decrease stability on southerly aspects by the afternoon. Solar influence on snow surfaces becomes stronger later into the year. Watch for snow surfaces to become wet and easier to penetrate as a sign of wet loose avalanche potential. The snow around rocks and cliffs will warm up earlier in the day.

Avalanche Discussion

Today we are expecting another beautiful day in the mountains. Unfortunately that gusty Wydaho wind decided to increase over the last 48 hours. Wind affect was very obvious yesterday while traveling in the alpine, and at least one wind slab was triggered outside the JHMR boundary in the backcountry. Pay attention to where the wind has drifted snow in peculiar ways as direction has varied with 439 miles of total wind in the last 24 hours (JHMR Summit weather station). Some models are showing increased wind speed up to 30 mph by the afternoon with gusts to 45 mph. Quick hand shear tests and identifying potentially wind loading areas will help you manage this problem today. Pay attention to heating of snow surfaces on southerly aspects with clear skies and temperatures reaching 30°F in the upper elevations. As for the persistent slab problem… it is persisting. Slopes with a particularly shallow snowpack or something such as triggering a cornice is how you could impact those buried weak layers. Seek slopes with a thick snowpack where the overlying slab is deep and difficult to impact. Splitting hairs between where the snowpack is thin or deep can be difficult. Default to riding less consequential terrain to manage the problem with more certainty.

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