Lawinenlagebericht

Tetons

Bridger-Teton Avalanche Center
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Lawinengefahr

Sun
Hochgebirge
4 · Gross
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

Human triggered avalanches will be likely at all elevations today, with very dangerous avalanche conditions above 9,000 feet.   Most of these avalanches will involve the recent storm snow, which is closing in on 4 feet in the last 48 hours.  There remains the possibility to trigger a very large avalanche on a deeply buried weak layer in isolated areas. The slopes with unsupported terrain features on the southern half of the compass are the most suspect but overall very dangerous avalanche conditions exist.  

Lawinenprobleme

  • Wind Slabs

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

    The Tetons have received 17-27 inches of new snow in the last 24 hrs, and up to 40 inches of snow in the last 48 hrs. This has built wind slabs that are in excess of 3-5 feet thick and sensitive to human triggering.

    This snow lies on a variety of old snow surfaces including, but not limited to, sun crusts, windboard, laid down surface hoar, and possibly small near surface facets. A  stong cold front is scheduled for this afternoon/evening which should signal a peak in natural avalanche activity.  

    Monitor the wind direction and look for evidence of cracking within wind drifted snow. 

    (1/27/2023)

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–3.5

    A weak basal structure highlighted by the November 27 crust/facet layer is present on previously wind scoured aspects. This layer is 20 to 60 cm above the ground and 50 to 100 cm down from the surface in areas that correspond to the highest likelihood of human triggering. While finding the trigger point is unlikely, the resulting avalanche will be very large.

    Upper elevations in the Tetons have received over 3 inches of snow water equivalent in the last 48 hours. 

    Today's continued snowfall will increase the number of possible triggers through sloughing, cornice failure, loading, tree bombs, and other smaller avalanches. Settlement rates have been hard to calculate during the intense snow fall but Rendezvous Bowl has likely seen around 11 inches of settlement in the last 24 hrs. The temperature trend for today is a gradual decrease. Sunshine remains unlikely today.  

    The only way to rule out this problem is by digging a hole in or near the slope you plan to ski or ride. 

    (1/16/2023) Slide initiated on skiers far upper left side of crown in shallower snow and propagated into deeper snow.

  • Storm Slabs

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

    Storm snow totals are closing in on 48 inches in the last 48 hours, with snowfall rates throughout  today in the 0.5- 1 inch/hour range. Storms slabs will probably be less reactive than yesterday but sizes are increasing from 1-2 feet plus.

    This snow lies on a variety of old snow surfaces, including - but not limited to - sun crusts, windboard, laid down surface hoar, and possibly small near surface facets. A well defined frontal passage is on deck for this afternoon/evening which should signal a peak in natural avalanche activity.

    Dry loose snow avalanches are a very real concern in steep terrain. 

    (1/27/2023)

Avalanche Discussion

In the last 24 hours the Tetons have received 17-27 inches of snow at the middle and upper elevations. Snowfall amounts are closing in on 4 feet in the last 48 hours in some locations, with snow water equivalent totals reaching 3 inches. Winds have been westerly in the 10-20 mph range and should continue in that range today. It doesn't take a rocket surgeon to realize that dangerous avalanche conditions exist.  

Have bumped the low elevations to considerable for today but maybe this is a bit too retroactive. Overall sensitivity of wind slabs and storm slabs should decrease today but depths aren't going anywhere. Wind slabs should continue to increase in spatial distribution where as storm slabs may shift to areas where the most recent crust has been buried. 

Avalanches, both human triggered and natural, were observed throughout the range yesterday but viewing conditions were less than ideal. Snowfall will continue today with the west side of the Tetons being favored with post-frontal orographics. 

This is a welcome reprieve from a relatively dry NNW flow regime that has left the Tetons with a variety of snow surfaces and riding conditions. Prior avalanche activity was confined to wind slabs in the alpine and some dry loose activity.  

Current snow depths range from less than a meter on previously wind scoured aspects to well over 2 meters deep on leeward aspects at the upper elevations. Westerly winds will work to cross load southerly slopes today and build overall slab thicknesses. Significant settlement (and subsequent slab cohesion and tensile strength) should occur over the next 48 hours or so.  

 

 

 

 

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