Avalanche forecast

Snake River Range

Bridger-Teton Avalanche Center
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Avalanche danger

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

Triggering a large avalanche that fails on weak snow buried 2-3 feet deep is possible in very steep terrain today. In addition, an incoming storm will bring new snow and wind to the area beginning around noon. Triggering a newly formed wind slab up to one foot in depth may become possible in steep, wind loaded terrain at the upper elevations by the afternoon. Avalanches are unlikely in the lower elevations except for in isolated pockets of very steep terrain.

 

Avalanche problems

  • Persistent Slabs

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

    Triggering a large avalanche that involves weak layers of snow buried 2-3 feet deep is possible in very steep (>35°), rocky, and unsupported terrain. Signs of instability such as cracking or collapsing may not be present before triggering. A significant natural avalanche cycle involving these layers occurred at the tail end of the most recent storm four days ago (2/19). Avalanches involving these layers were observed on a variety of aspects at all elevation bands. The likelihood of triggering has decreased over time, yet it is worth keeping this problem on the radar in suspect terrain (see photo) given the consequences of being involved in avalanches of these sizes. Practicing safe travel habits such as skiing one at a time, stopping in islands of safety, and communicating with partners are ways to increase safety margins in avalanche terrain.

    A large avalanche in the southern Tetons that likely occurred around 2/19. This terrain is very steep, cliffy,  and has produced multiple avalanches in the past 10 days.

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    The Snake River Range could receive up to 5 inches of new snow in the upper elevations by the evening. Strong winds out of the west/southwest will redistribute loose snow and create new soft slabs up to a foot deep on leeward slopes. These slabs will be small, but could become sensitive to the weight of a rider in very steep (>35°) wind loaded terrain at the upper elevations by the afternoon. Be on the lookout for signs of instability in wind drifted snow such as cracking or collapsing and consider moving to lower angle terrain if these signs are present.

Avalanche Discussion

Today’s avalanche problems primarily involve weak layers in the middle of the snowpack. Storms between Feb 14th and 19th deposited 4-5 feet of snow throughout the Snake River forecast zone. This added significant stress to underlying weak layers. In the past 4 days, the snowpack has had some time to adjust to this load. This translates to a gradual decreasing trend of avalanche activity. Despite this trend, it remains possible to trigger an avalanche at these depths. The likelihood of triggering increases as the slope angles increase and when large triggers (groups, multiple snowmobiles) hit thin spots in the slab. Thin spots exist on the boundaries of terrain that have been impacted by the wind and are more problematic when the snowpack connects to thicker slabs within that same terrain. In periods of improving stability, it remains important to follow safe travel practices despite a general lack of avalanche activity. Travel one at a time in steep terrain, avoid stopping in the runout of avalanche paths and communicate with your partners throughout the day.

Conditions will change today with an incoming storm after several days of relatively quiet weather. Southwest winds picked up yesterday and will continue to move snow today. Forecast models indicate that new snow should start around midday, however, predicted accumulations vary between 3-5 inches for the Snake. Newly formed wind slabs will be on the radar in the uppermost elevations this afternoon if we receive the high end of the forecasted totals. However, these slabs will not be large or widespread enough to elevate the avalanche hazard. Keep an eye out for loading and slab formation to avoid being surprised in avalanche terrain.

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