Lawinenlagebericht

Snake River Range

Bridger-Teton Avalanche Center
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Lawinengefahr

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

Triggering an avalanche involving wind drifted snow is possible at the upper elevations today. Slabs will be 1-2 feet thick and may be sensitive to the weight of a rider in very steep, wind loaded terrain. Rocky alpine terrain is most suspect. Carefully evaluate the snow for signs of recent loading before committing to a slope.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Wind slabs up to two feet deep were formed three days ago across a variety of aspects in the upper elevations. These slabs are stabilizing with time and static weather. As a result, the likelihood of triggering an avalanche involving wind drifted snow has decreased over the past 48 hours. Still, riders may be able to trigger a slab in very steep alpine terrain. Loaded ridgelines, rocky areas, and cliff bands are most suspect. Daytime heating may increase the sensitivity of lingering slabs. Carefully evaluate any steep terrain with evidence of recent wind loading.

    A skier triggered avalanche on No Name Peak on Dec 28th resulted in the skier being caught and carried but not buried. 

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    1.5–3

    Significant loading and abnormally warm conditions at the tail end of the last storm cycle produced several very large natural avalanches involving interfaces deeper in the snowpack. A widespread rain crust that formed on December 10th is present in the middle of the snowpack. Weak snow from November exists not far below this crust on shady slopes above 8,500’. The sensitivity of these layers has rapidly declined in recent days making deeper avalanches very unlikely today. However, these events cannot be ruled out completely given a large enough trigger. Surface avalanches or a large cornice fall could be enough to impact deeper layers. If triggered, slabs will be 3-6 feet deep.

    A very large natural avalanche in No Name Canyon in the southern Tetons that likely occurred late in the day on Dec 27th.  Crown depth estimated at 4-5 feet.

    HS-N-R3-D3

Avalanche Discussion

A series of atmospheric rivers delivered significant precipitation in the form of both rain and snow over ten days lasting from 12/16 through 12/27. This active weather pattern created a variety of short lived storm instabilities as well as a crust up to 9,500 feet that formed on Christmas day. During this period, the upper elevations received over 8 inches of Snow Water Equivalent (SWE). Periods of strong winds amplified loading rates and created unstable conditions. This is a significant load in a relatively short amount of time. 

With precipitation tapering off 60 hours ago, the snowpack has moved into a period of stabilization. Cold temperatures in the wake of the wet and warm period are helping to speed up the adjustment of the various interfaces within the upper 3-5 feet of the snowpack. The reactivity window for deeper instabilities has likely passed, though the recent events in No Name Canyon and Mosquito Creek are worth studying. Closer to the surface, the Christmas crust and potential weak grains that surround it appear to not have enough of a load to pose a significant threat at the moment. This layer will be closely monitored during future loading events.

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