Lawinenlagebericht

Tetons

Bridger-Teton Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
2 · Mässig
Waldgrenze
1 · Gering
Unterhalb
1 · Gering
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Kernpunkte

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.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–1.5

    The Tetons could receive up to 5 inches of new snow in the upper elevations by the evening. Moderate to strong winds out of the west/southwest will redistribute loose snow and create new soft slabs up to one foot in depth on leeward slopes. These slabs will be small, but could become sensitive to the weight of a rider by the afternoon in very steep (>35°) wind loaded terrain at the upper elevations. 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.

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    1.5–2.5

    Triggering a large avalanche that involves weak layers of snow buried 2.5-4 feet deep is currently unlikely and limited to isolated pieces of very steep terrain (>35°). 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. Despite the likelihood of triggering being on the low end of the scale, 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 on the Pyramid that likely occurred around 2/19. This terrain is very steep, cliffy, and has produced multiple avalanches involving mid-snowpack weak layers  in the past 10 days.

Avalanche Discussion

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 Tetons. 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. 

Weak layers including a rain crust and a thin layer of facets formed 2/4-2/6 are now buried 2-3 feet deep in the Tetons. Older facets and crusts formed during the second half of January are buried 3-4 feet deep. All of these weak layers have been tested by a considerable amount of water weight (~12"!) in the first half of February and have since had time to adjust to the loading. These layers have held up to the test in the majority of terrain. However, the recent natural avalanche cycle that occurred around 2/19 indicates that very steep, heavily loaded, and unsupported slopes near cliff bands were most likely to fail. New snow from the incoming storm shouldn’t add enough weight to the snowpack to significantly increase the likelihood of triggering a persistent slab avalanche and the overall stability trend with regard to these layers should continue to improve with time.

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