Bulletin d’avalanche

Blues

Wallowa Avalanche Center
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Danger d’avalanche

Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Points saillants

Sunshine and warm temperatures are on tap for today and tomorrow which means melting and weakening in our upper snowpack. Above freezing temperatures will effect the snow at all aspects and elevations today,  with the exception of north facing terrain at the very uppermost elevations.Steep solar aspects (>35 degrees) will be affected by the destabilizing effects of the warm temperatures  the most dramatically. The later in the day a rider lingers on these steep and sunny slopes the greater the likelihood of triggering a wet loose avalanche or wet slab avalanche. When we are experiencing a melt freeze cycle like the one we are currently experiencing, it is best to get on the snow early when it is firm and strong and get off the snow in the early afternoon before it becomes soft, mushy and weak.

Problèmes avalancheux

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    By late morning expect to see temperatures well above freezing, even as high up as 8500' . Temperatures are forecasted to be in the 40's today, mid 50's in the Blues and Elkhorns. This warming will cause the snow surface to weaken and become unstable resulting in loose wet avalanches on steep (>35 degrees) sun drenched east, southeast, south, and southwest facing terrain. Classic signs that the  snow is becoming weak/ unstable at the snow surface are the presence of roller balls/pin wheels, wet mushy surface snow, and snow that allows you to sink up to your boot tops when walking in it. The gold standard for recreating in wet spring snow is get on the snow early while it is strong and supportable, and get off the snow before or as soon as you start to see the obvious aforementioned signs of instability (early afternoon). Even though wet loose avalanches are slower moving than dry avalanches, the wet loose avalanche can entrain a lot of heavy wet snow making it a potentially powerful force that could carry a rider into a situation with undesirable consequences.

  • Wet Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    If the air temperature is warm enough,  and the melting process goes on long enough, melt water will percolate down into the snow pack decreasing the strength of a buried weak layer. Or that meltwater could start pooling upon an impermeable crust layer causing the bond at that crust layer to weaken and eventually fail. Either way, the result could be  a wet slab avalanche. Look for this to occur on sun drenched terrain steeper than 35 degrees. In my travels in the Northern Elkhorns yesterday I dug down a couple of feet into the snow to see if I could observe this percolation process of melt water down to the Mid March melt freeze crust,  in several locations. That melt water percolation process was not happening at the locations I observed yesterday but that's not to say that the melt water percolation process won't happen today because temperatures stayed above freezing last night. Potential  wet slab problems are worth mentioning today because wet slab avalanches, although hard to trigger, can be large and destructive and you do not want to get caught in one. Once again, best practice in these conditions  is to get on the snow early and get off the snow early, preferably before the snow gets mushy, before you start seeing roller balls/pin wheels, and before you find yourself sinking up to your boot tops in the snow. Avoid being on or underneath any steep slope you suspect has the potential to produce a wet slab avalanche.

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    It is easy to trigger a cornice failure during periods of sunshine and above freezing temperatures because warming has a destabilizing effect on cornices making them easier to break under the weight of a human (or canine). Keep in mind cornices tend to break further back from the slope edge than you might expect. Stay well back from slope edges when traveling near ridgelines unless you are certain you are not going out on a cornice. Always give cornices a healthy dose of respect, especially when the sun is out and temperatures are above freezing. 

Avalanche Discussion

All of our weather stations were showing that temperatures stayed  above freezing last night with the exception of Schneider Meadows. I would expect the snow to be soft this morning getting softer and weaker as soon as the sun comes up and starts to warm the air and snow surface. Expect to see signs of instability such as roller balls and wet, mushy, unsupportive snow by late morning. As soon as we take notice of the obvious signs of instability we need to get off of and out from under these potentially unstable slopes steeper than 35 degrees. Today the avalanche danger level is rated "moderate" but as temperatures continue to rise late morning the danger level could move move into the "considerable " category.

Régions couvertes