Bollettino valanghe

Salt River and Wyoming Ranges

Bridger-Teton Avalanche Center
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Pericolo valanghe

Wed
Alta quota
3 · Marcato
Limite del bosco
4 · Forte
Sotto il limite
3 · Marcato
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In sintesi

Travel in avalanche paths is not recommended today due to above freezing temperatures last night and the warmest temperatures since November today. Large, natural wet loose avalanches remain likely at most elevations and many aspects with larger, wet slab avalanches becoming likely as well. Large cornice failures are also possible today. Cautious route-finding will be required to find, manage and avoid these hazards.  Reduce your time spent in large and very steep avalanche paths today and avoid them altogether if you find wet, slushy snow underfoot, cornices overhead or warm temperatures and low wind speeds nearby.

Problemi valanghivi

  • Loose Wet

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

    Yesterday's warm sunshine and low wind speeds triggered widespread wet-loose avalanche activity. Many of these avalanches were large enough to bury a person. Warm temperatures last night did not refreeze the surface snow enough to reduce this problem today.  While many of the steepest and most vulnerable slopes may have released yesterday, continued warmth overnight and today will keep this hazard in play today, especially for human-triggering. If you've ever experienced the force behind moving wet snow, you'll understand the danger of even small slides.

    The huge cornices that our copious snowfall has produced this winter continued to wartm and sag from ridgetops overnight. Wind may help to cool them to some extent today but warm ambient temperatures will continue to strain them. Falling cornices can trigger the other wet snow avalanche types in addition to to their intrinsic hazard.

     

     

    (4/9/2023)

    Wet loose avalanches occurring ~2 PM at lower elevations despite rapid melt occurring and bare ground present; wind-loaded slopes will still have enough snow volume to move longer distances. 

    Photo: Antonioli

  • Wet Slabs

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

    The upper snowpack above persistent layers buried 2-3' deep has been exposed to warm temperatures for several days now with no refreeze last night.The natural wet slab avalanche that was observed int he Gros Ventre (see photo) yesterday may be the harbinger of more slab failures today. These slabs could fail naturally or be triggered by a skier or rider, by a cornice fall or by wet loose snow sluffing in steep terrain. The potential destructive power and potential size of this avalanche type should have you factoring it into your terrain selection.  It's worth noting that the thin areas that exist in the snowpack are the most likely spots for slab failure. The slab in South Park is good example of this and indicative of a the problem that seems likely exist at higher elevations today due to the increasing temperatures last night and today. The location graphic shows this problem at all aspects due to warm ambient temperatures but sunlit slopes, especially thiose exposed wet loose avalanches or cornice falls are the most likely areas that you'll find this problem.

     

    (4/10/2023)

    Wet avalanches on a SW aspect at 7,800' near Wilson (South Park) in the northwestern Gros Ventre range. One large wet slab is shown that is about 400' wide. Three or four large point releases are also shown, all of which ran about 1200'. These likely occurred during maximum heating on April 10.

    Photo: Frank Carus

Avalanche Discussion

The equation for wet snow avalanches is challenging to solve today.  The solution may be found in the warming ambient temperatures overnight combined with an unknown amount of solar input today minus the cooling effect of southwest winds and the shedding that occurred yesterday. If you prefer simpler arithmetic, the solution can be viewed (safely outside of avalanche terrain) mid-day at the confluence of strongest solar gain of the day, the warmest ambient temperaturess since November, both following a warm night with above freezing temperatures. It is possible that the cooling power of the wind and building cloud cover will reverse the warming trend currenly going on and stop the flow of water through the snowpack at some point today but the question remains exactly when this will occur. The wind speeds and the cloud cover this afternoon are the two factors that kept me from pulling the trigger on a high danger rating at mid-elevations in the Tetons today and are pivotal for stopping larger and wide-spread avalanches today.  The Greys River zone has had poorer structure throughout the winter and is generally warmer during this period of high pressure. Careful snow and weather evaluation is the name of the game today if you choose to venture into the mountains today.

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