Avalanche forecast

Tetons

Bridger-Teton Avalanche Center
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Avalanche danger

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

Human triggered avalanches are possible at all elevations in the Tetons today. Areas where the wind has stiffened the new snow into slabs that overlie slick crusts and buried weak layers are the primary concern. Pay attention to signs of instability such as audible collapsing of the snowpack and cracking within wind affected snow. Use your shovel to dig into the snowpack and determine whether weak snow or crusts are present below the new snow on the slopes you plan to ski or ride. 

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Avalanche problems

  • Wind Slabs

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

    The Tetons picked up 30 to 40 inches of snow from February 19-23. Westerly winds prevailed at the beginning of the storm cycle but veered to the North and eventual the East by the end of the cycle. This has resulted in wind slabs that are generally 18-24 inches deep on a variety of aspects at the upper elevations, but could be up to 3 feet deep in favored locations. On the northern half of the compass these slabs are failing on a density change within the new snow or on the new snow/old snow interface (Feb 18). On the southern half of the compass these slabs are failing on a slick crust at the new snow/old snow interface (Feb 18). These slabs could be both soft (4f) and hard (1f). Wind pressing from easterlies at the end of the storm as stiffened slabs on unusual aspects. 

    Pay attention to signs of instability such as cracking within wind drifted snow. 

    (2/23/2023) Starting zone, with ski tracks (up & down) on ridge to looker's Left

  • Persistent Slabs

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

    Weak faceted snow and slick crusts exist at both the new snow/old snow interface (Feb 18) and lower in the pack. The Jan 26 crust/facet combo is buried 60-80 cm below the surface of the snow on southerly aspects. Triggering avalanches from a distance (remote triggering) is possible. 

    Pay attention to signs of instability such as audible collapsing of the snowpack. Your best line of defense against a persistent slab problem is to dig a snowpit in a representative location and perform some stability tests such as an Extended Column Test. 

    (2/23/2023)

Avalanche Discussion

The Tetons have picked up a trace to 1 inch of snow in the last 24 hrs, with most of that snowfall occuring in the early morning hours yesterday. A closed low off of the California/Oregon coast will spin up small amounts of moisture into western Wyoming today in a SW flow. Scattered snow showers are expected today with some possible windows of sunshine in the afternoon. Winds will be out of the SW gusting into the 30s. Temperatures will reach the upper teens on the peaks and mid twenties in the valleys. 

Recent avalanches have been observed at all elevation bands on a variety of aspects up to size 2. These avalanches have failed within the new snow and at the new/old interface. It is unknown if any avalanches have occured on the Jan 26 layer (or other buried persistent weak layers). In my mind human triggered avalanches will most likely occur near the new/old interface on North and East aspects (slab depths 18-24 inches, possibly deeper). On southerly aspects failure at the Jan 26 interface remains a very real concern, especially at the middle elevations (slab depths 18-24 inches).  As is common with most storms in the Tetons that are rather windy, avalanches starting below traditional starting zones ( i.e. below cliff bands) need to be considered. 

The new snow/old snow interface lies 30-40 cm down on the southern half of the compass and closer to 60 cm down on the northern half of the compass. This interface is a crust on southern aspects and near surface facets on northern aspects. The January 26 crust/facet combo lies 60-80 cm below the surface of the snow at upper elevations on the southern half of the compass. The last known human triggered avalanches associated with this layer occured in the wake of the major storm event at the end of January and early February, but some of the recently observed avalanches at the lower/middle elevation interface could be on this layer. The November 27 layer generally lies 1-2 meters below the surface of the snow at upper elevations on the southern half of the compass. The last known human triggered avalanche associated with this layer was on January 16.  

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