Bollettino valanghe

Togwotee Pass

Bridger-Teton Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
Senza grado
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Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

New snow and wind will make triggering a soft slab avalanche likely in steep, wind loaded terrain at the upper elevations. Triggering a deeper avalanche that fails on weak layers buried 2-4 feet deep remains possible and poses a larger threat. Be prepared to move to low-angle terrain if you observe instability in the new snow, such as cracking or collapsing. Careful snowpack evaluation and conservative decision-making are recommended around avalanche terrain today.

The NWS has issued a Winter Storm Warning that is in effect until Friday, 11:00 PM.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–3

    Several feet of recent snowfall has fallen on a weak snow interface. This interface is now buried beneath a slab of snow that is 2-4 feet thick and, if triggered, can propagate across large distances and make escape impossible. Obvious signs of instability, such as cracking, collapsing, or recent natural avalanche activity, are not likely to present themselves before triggering a large avalanche.  Entering terrain over 35 degrees will increase the odds of triggering an avalanche today. Keep terrain choices simple by sticking to lower-angled terrain and be especially wary of the creekbeds and flat terrain that create unsurvivable terrain traps.

    Weak snow near the base of the snowpack lurks 2-5 feet below the surface. New snow and wind are stressing these weak layers. Avalanches involving these layers could occur with a significant trigger, such as a large wind slab avalanche, a passing snowmobile, or a group gathered below a slope. 

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Three inches of snow fell overnight; an additional 5-10 inches are forecasted to fall today, with W/SW winds gusting 45-55 mph. Uncertainty exists in the weather forecast; if snowfall amounts trend towards the higher end, expect the hazard to rise. Sensitive wind slabs will grow in size and distribution as you move higher in elevation.  The best way to avoid this problem is to avoid steep slopes or consequential terrain where you find indications of recent wind loading. Watch for snow that is denser than snow found on wind-sheltered slopes and tell-tale clues such as surface texture and a pillowed, drifted appearance. 

Avalanche Discussion

It's time to take stock and make sense of the complex new layer cake existing in the top meter of the snowpack. Today, primarily, be on the lookout for new snow instabilities. Here is some food for thought as we look forward to more "boots on the ground" observations in the coming days. Let's consider what we do and don't know.

Observations so far (knowns):

  • Limited observations from this zone make inferring a pattern in the weak snow buried 1/31 uncertain here.
  • Not much natural avalanche activity has been observed on the 1/31 weak layer, but lack of evidence does not imply evidence of lack.

Observations needed (unknowns):

  • Will the crust/facet layer buried 1/31 on steep, sunny slopes be a thing or not? Sometimes, trends seem to appear simply due to observation bias. 
  • How will 1/31 age on all aspects?
  • How will new snow bond to the graupel/mixed bag interface today?

Until we get a better handle on our brave new world and the "knowns" list is longer than the "unknowns," I'll be embracing a wait-and-see attitude.

Please continue to send in your observations. Thanks!

 

 

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