Lawinenlagebericht

Tetons

Bridger-Teton Avalanche Center
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Lawinengefahr

Sat
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist 2 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Areas favored by the storm last night formed shallow wind slabs in the upper elevations sitting on weak interfaces. Look for signs of wind drifted snow on open and exposed terrain, such as cracking, stiffened surfaces, and large pillows. The possibility of wet slab avalanche activity remains on steep southerly aspects with daytime temperatures above freezing across all elevations.

Lawinenprobleme

  • Wind Slabs

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

    A quick pulse of snow favored the northern areas of the zone with 5-7” of snow overnight. This snow was accompanied by a quick burst of SW wind over 20 mph forming slabs less than 12” deep on specific wind loaded terrain in upper elevations off ridgelines and open, exposed slopes. The new snow sits on weak interfaces formed over the last week including facets on sheltered N aspects and widespread crust on W-S-E aspects across all elevations. Watch for new snow instability across all elevations. Assess new snow instability by performing quick hand shear tests and looking for those signs of wind loaded slopes.

    (3/14/2024)

    Cracking snow surfaces, a sign of instability on wind loaded terrain.  

    Photo: Alex Drinkard

  • Wet Slabs

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

    A week of warm weather continuing today has allowed free flowing water to move through the snowpack creating wet slab avalanches. Only two avalanches were reported on 3/19, both human triggered (Bernie's Bowl, Wolf Trap). Even though temperatures are decreasing, water is still moving through the snowpack making this type of problem difficult to predict. Therefore, it remains possible to trigger a large avalanche 1-2 feet deep on southerly aspects, especially around rock features. Temperatures are forecasted above feezing once again across all elevation bands. Today's partial cloud coverage, and slightly cooler temperatures will continue trending this avalanche problem towards unlikely.  Pay attention for signs of warming. Monitor snow surfaces today for wet and slushy surfaces where you are sinking into the snow in the afternoon and seek colder, shaded terrain. 

    (3/19/2024) This avalanche was triggered by a snowcat pushing snow onto a ski slope Tuesday afternoon. 

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    2–3

    Weak snow formed in December is persisting 3-5+ feet deep below hard slabs.The last reported avalanches occurred on 3/5 after a rapid and large loading event. These occurred on heavily wind loaded terrain and below cornices. The impact of a rider triggering these layers is unlikely. Still the primary terrain that is most hazardous includes very steep, unsupported slopes above cliffs and rocky or notably shallow slopes on the north half of the compass. Thin spots in the snowpack are more likely to act as trigger points in these locations. Larger triggers, like a cornice fall or surface snow avalanches, still have the potential to impact weak layers buried deeply in the snowpack and initiate a much larger avalanche.

    (3/5/2024)

    Very large persistent slab avalanche that failed during the early March storm cycle. This terrain characterizes where this problem is most active. Very steep, unsupported slopes near cliffs. Also note the large cornices and potential trigger. 

    Photo: Dan Hays

Avalanche Discussion

Snow returns!

A shortwave trough brought variable snowfall amounts to the Tetons, favoring the west and east side on the northern portion of the range. A total of 5-7” of new snow was accompanied by moderate winds. These winds tapered off quickly, so wind slabs will remain shallow and less than a foot deep. Wind is forecasted to stay below 20 mph today. The weak surfaces formed prior to this storm will be a concern today even in wind sheltered terrain, as new snow could move easily on the widespread crusts and near surface facets formed on specific northerly slopes. Watch for the new snow to become more reactive during the day as temperatures increase, especially on southerly aspects with clear skies and solar influence. Dry loose will also be a concern knocking riders off their feet  (unlikely to affect snowmobilers due to shallow new snow depth) where crusts exist below the new snow.

There’s also the potential for wet slab avalanche activity to continue today. Consistent warm temperatures above freezing allows free water to move through the snowpack. Free water in the snowpack can have a "lag" effect, meaning it takes time to move through the snowpack and drain or re-freeze. Hence why these wet slabs can still be reactive even with the cold night time temperatures and decreasing daytime temperatures. Wet slab avalanches are difficult to predict, even for professionals. This problem exists on southerly aspects, especially around rock features that absorb heat and intensifies the warming of snow around them. Seek sheltered, shaded aspects as both the danger and riding quality will be better. Just watch out for those wind slabs and new snow instability on steep slopes.

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