Lawinenlagebericht

Tetons

Bridger-Teton Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

Dangerous avalanche conditions exist today and human triggered avalanches are likely. Since Thursday morning, some areas of the Tetons have received over 4 feet of new snow. Steep terrain at the mid and upper elevations, where wind enhanced the formation of cohesive slabs will be the most sensitive to recreational skiers and riders. At lower elevations, slides could be triggered in wind loaded areas or in other very steep terrain where the snowpack has not yet adjusted to the recent, rapid loading. Although conditions are less sensitive than the past 2 days, any steep terrain is suspect today and conservative terrain selection is the best way to avoid an avalanche accident.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2.5

    Approximately 4 feet of recent snow, containing 3 inches of water, and moderate winds that were generally from the west/northwest but are now backing to the south have loaded steep avalanche starting zones. These slabs have become less sensitive but can still be triggered by a single person. This could occur while approaching a slope or once one is exposed and several turns into a run. Slabs could be shallow, failing on density changes within the new snow or fail on the storm interface buried on Thursday to a maximum of 6 feet. 

    (1/28/2023)

    Diamond showing crown depth of a remotely triggered avalanche on 25 short. This avalanche failed on a thin layer of buried near-surface facets under recent snowfall. 

    Photo: Antonioli

  • Storm Slabs

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

    Recent snow could be triggered as loose snow sloughs or as soft slabs at the low elevations. Events of this nature were occurring naturally on Friday and Saturday morning and are still possible today. Although relatively small, they could have depths to 18 inches and quickly cause problems in small terrain traps. 

  • Deep Persistent Slabs

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

    Deeply buried weaknesses exist in the snowpack on certain aspects above 8000 feet.  Today these slabs are most likely to fail following the triggering of a large wind slab but cornice failure or a group of people impacted a thin and weak spot on a slope could also possibly cause failure. If triggered, these slabs will be hard, very large and destructive. Clearing skies will provide an opportunity to see if any such events happened during the rapid loading when natural wind slab activity was occurring. 

Avalanche Discussion

The rapid loading that occurred during this storm event is very uncommon in the Tetons.  The rendezvous bowl plot recieved almost 50 inches of snow in 50 hours. On Friday, the snow 6% snow was falling on lighter snow, surface hoar, near surface facets and firm surfaces such as sun-crusts and wind pack. The rapid snowfall, resulted in widespread natural activity with relatively low volume debris on Friday. By Saturday morning, the amount of new snow accumulation was becoming more problematic. Although slabs at higher elevations were slightly less reactive, they were upside down and when triggered, involved higher volume. Very steep terrain at low and mid elevations were releasing and steep banks impacted roadways in canyons, town, and on Teton Pass. Many avalanches were reported to the avalanche center although the bulk of the backcountry was obscurred and recreationalists generally backed off onto lower angle slopes. 

Today is different. Avalanche conditions are not as blatantly obvious or sensitive and  deserve more thought and respect.  Although some slopes may release upon approach, most slabs will have become more stubborn from settlement and cold temperatures and slab initiation may not occur until on the steepest part of the slope or on a convex rollover mid-slope. Use caution and avoid known avalanche paths as lower angle terrain is the best way to avoid an avalanche accident today.  Do not let powder frenzy or ambitious goals cloud judgement during the first clearer day following a four foot storm. 

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