Bollettino valanghe

Togwotee Pass

Bridger-Teton Avalanche Center
Vedi sulla mappa

Pericolo valanghe

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

In sintesi

Several layers of weak snow are buried in the snowpack. Recent snowfall has added weight to these weak layers. As the likelihood of triggering an avalanche on any deeper layers gradually decreases, the possibility remains, particularly with changing weather conditions and rapid warming. Make your terrain selection accordingly and be alert to the consequences of being caught in a slide where you are traveling. Bright sunshine between periods of clouds will change the snow surface and increase the hazard, particularly in steep or rocky terrain. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2.5

    As we move away from the incremental loading events that brought improved skiing and riding conditions to our area, we focus our attention on the persistent weak layers that are buried in the snowpack. The primary culprit remains the Feb 18th facet+crust layer now buried 1-2’ below a firm, cohesive slab. Recent avalanche activity on this layer is expected to gradually decrease over time, however active weather throughout the week means we need to continue looking for this layer and assessing its activity of it on our slope of choice. This combination is found on the southern half of the compass at the middle and upper elevations. Lower elevations contain this same combination, as well as just generally weak snow on sheltered aspects. 

    The best way to assess this weak layer is to dig down, identify the layer, and perform stability tests before riding consequential terrain. It is worth carefully reading any recent observations over the past week in areas you frequent and grasp any trend with activity. You are most likely to encounter this problem on terrain that has the following characteristics:

    • Located on the southern half of the compass at upper elevations (E-S-W): These areas remain shallower and weaker as any new slab builds.
    • Wind-affected: Terrain where the wind has formed firm, cohesive slabs of snow. 
    • Steep: Terrain over 35 

    Recent avalanche activity has occurred on this layer in areas with a thin, shallow snowpack such as the Wyoming Range, which bears similarities to Togwotee. (Dry Creek Lake, Hoback Peak).  

  • Wind Slabs

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

    Continued wind transport was observed yesterday in the alpine terrain of the Greys River and Teton zones. These wind slabs are becoming less sensitive to the weight of a skier or rider, but some are sitting atop weak snow surfaces (facets and/or crusts) and remain touchy.  Recognize that wind-loading also adds stress to the weak layers buried in the snowpack (described in Problem 1 above). Any wind slab you trigger could step down to deeper layers, producing a much larger, more dangerous avalanche. While the slabs you encounter today are less likely to be large, they may produce slides large enough to knock you off your feet and send you downslope. Look for evidence of wind drifting such as dune-like drifts and ripples on the snow surface. Cracks shooting out from your skis or board are a sure sign that you've found a sensitive wind drift. 

    ADDITIONAL DISCUSSIONDirect sunshine on fresh snow is a recipe for loose snow avalanches. Variable cloud cover and winds blowing out of the SE will both help to keep the snow surface cool, but the intense March sunshine will quickly melt the snow when it breaks free from the clouds. Be aware of prolonged periods of sunshine and how that is altering the snow surrounding you. Moving forward into March, you're most likely to encounter this problem on very steep, rocky slopes that directly face the sun. 

     

Avalanche Discussion

Wait For It

I usually think of March as the time to break out the ol' Hawaiin cutoff shirt, and my mind turns to the joys of wearing flip-flops post-ski-boot torture. But as we step into this month, we sit yet again in the crosshairs of an atmospheric river event arriving late this week.  Significant weather patterns are still heading our way. Last season, a relatively dry and locked-in mid-winter snowpack got some large late-season large storms. This season's pack is a different beast and will pan out in a variety of ways depending on the weather we see in the future. This cake has layers and will get even more, and some may be mayonnaise instead of frosting. It's worth testing the waters before taking a big bite.   Temperatures will warm a bit more each day throughout the remainder of the week and as more water is headed our way. In the long term, warm temperatures and more water will eventually help to increase the stability of the snowpack. However, this process takes time and isn't always pretty. I expect the snowpack this year to behave unpredictably through this transitional period.

If you're out in the backcountry today and after our next large storm on the weekend, be aware that you are encountering a snowpack that is in the throes of change. Rapid changes are rarely pretty, and they often produce difficult-to-predict conditions. If we are lucky, shifts in weather patterns and entering into a more typical diurnal-spring flow will give our snowpack some time to heal the weak layers of snow buried within it. But don't expect that to happen in a day. Keep those layers of weak snow in mind as you travel and spend time thinking about the consequences of being caught in a slide in the terrain you are in.

Regioni coperte