Avalanche forecast

Tetons

Bridger-Teton Avalanche Center
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Avalanche danger

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

Persistent weak layers are still lingering in the snowpack where riders could trigger large avalanches in areas with a thin, shallow snowpack. Winds shifting and increasing out of the W/NW have formed shallow slabs on isolated terrain, especially in the alpine of upper elevations. Reduce your chances of triggering an avalanche by riding areas with a thick snowpack away from wind affected terrain.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    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. Although the likelihood is decreasing, the slight chance remains. Triggering an avalanche is most likely on steep slopes where the overlying slab is thin and riders can impact these weak layers. 

    • The most obvious slopes will be rocky and 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). 

    Stick to lower angle and less consequential terrain to reduce the unpredictable nature of persistent slab avalanches.

    (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.

  • Wind Slabs

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

    Watch for new, thin slabs on isolated terrain less than a foot deep formed from shifting wind. This wind shift out of the NW accompanied by increased speed around 20 mph formed fresh slabs starting yesterday afternoon. Pay attention to wind speed today as these slabs could increase in size with continued sustained winds. Stay alert in alpine terrain especially above the forecast area of 10,500’. 

    Cornice Falls: Wind throughout the winter has formed cornices on N-NE-E-SE-S aspects in the upper elevations. Two cornices were triggered two days ago indicating that cornices are becoming unstable. Give cornices a wide margin of safety and be careful along ridgelines.

    (2/19/2024)

    Wind pockets will vary in size and distribution at upper elevations in the Tetons. Choose terrain accordingly, and consider the consequences of even a small slide that rips in an unexpected way. 

Avalanche Discussion

The importance of paying attention to subtle changes in the weather can help keep you out of harm's way when traveling in the backcountry. Something as small as a slight wind shift can change snow conditions on a day to day basis. There’s plenty of snow available for transport with the slight shift and increase in wind speed. Rendezvous Bowl weather station interval board shows increased snow depth even though we haven’t received any precipitation indicating that wind loading is occurring. These slabs should remain small but could easily knock a rider off their feet or machine. 

In addition, we are still dealing with the persistent slab problem. It is difficult to determine how thick the snowpack is on a given slope. Local knowledge and understanding of snowpack while traveling in terrain can significantly improve your ability to avoid this problem. Gaining knowledge by finding out where that thin, shallow snowpack exists before committing to consequential terrain is important. Remember that persistent slab avalanches are difficult to predict. Choosing lower consequence terrain away from steeper slopes is the primary way to avoid this problem. 

February is coming to a close as we are transitioning to stronger solar influence later in the winter. Clear skies by this afternoon will decrease stability on southerly aspects. Pay attention to those subtle changes of snow becoming wet and loose by this afternoon.

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