Avalanche forecast

Elkhorns

Wallowa Avalanche Center
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Avalanche danger

Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Expect to find fresh and easily triggered windslabs (recent deposits of wind-drifted snow) on northwest, north, and northeast facing leeward  terrain at and above treeline, and especially near ridgelines today.  It could be very easy for a human to trigger an avalanche on leeward facing wind loaded terrain steeper than 30 degrees so cautious route finding and conservative decision making will be essential in order to move through steep wind affected terrain in the alpine. It would be advisable for the recreationalist to avoid wind loaded avalanche terrain altogether today.

 

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Avalanche problems

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    As temperatures warm to near freezing by late morning and early afternoon, there is a chance we could see wet loose avalanche activity on west, southwest, and south facing terrain below treeline on slopes getting baked by the sun. Sunshine and warm temperatures have a destabilizing affect on soft, newly fallen snow. Signs that warming temperatures are starting to weaken the snow include water droplets dripping off snow laden tree branches, and large clumps of snow (snow bombs) dropping off of tree branches. Other signs of heat induced warming include the observance of roller balls on the snow surface. You might start to first see rollerballs just below steep rock features. Or you might notice that, as the temperatures start to rise, you are seeing roller balls or loose wet sluffs as your skis, board, or sled travels through the warming snow. If we start observing these or other red flags of snow instability, we need to get off of and out from under these sunny aspects and move to shady and more stable north facing terrain.

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Moderate to strong southwest, south, and southeast winds were observed and recorded at weather sights yesterday and last night throughout our forecast area. Also, south and southwest winds strong enough to create windslabs on northwest, north, and northeast facing leeward terrain are forecasted today for the Blues, Wallowas, and Elkhorns. With plenty of light snow available for transport, expect to see fresh, sensitive  windslabs on leeward facing terrain at and above treeline and especially near ridgelines throughout the forecast region. Recent deposits of wind-drifted snow (windslabs) look like very large domelike pillows. Windslabs that are firm enough to support the weight of a human can have a hollow, drumlike sound and feel to them as well. Wind-drifted snow has a stiff, slabby feel to it that is noticeable while traveling through it on boards and snowshoes, not so noticeable if on a snowmobile. Red flags that warn of windslab instability include "shooting cracks" projecting out in front of ski tips, snowboard tips, or snow shoes, and the observance of avalanches in your area of travel. Today expect to find dangerous avalanche conditions on leeward facing terrain steeper than 30 degrees (avalanche terrain) especially near ridgelines. Today would be a good day to avoid traveling through avalanche terrain that is, or could be, wind loaded. Fresh windslab avalanches can be easy for a person to trigger and can take the unsuspecting recreationalist on a harrowing and uncontrollable  ride down the mountain. 

    (2/24/2023)

    Photo of moderate to strong southwest winds moving loose snow onto leeward facing slopes at ridgelines in the Northern Wallowas. Photo was taken Friday, February 24th in the afternoon.

    Photo: VM

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    We are still dealing with persistent weak layers (surface hoar and facets) buried at various depths in our snowpack in the Blues, Wallowas, and Elkhorns. I have been seeing these buried persistent weak layers at and below treeline on shaded and wind sheltered locations where the snow depth is 4' or less. These weak layers, once buried, persist in the snowpack for days or weeks creating poor bonds with the snow surfaces above and below. Most of the time, the only way to know if these persistent weak layers exist in areas where you might want to recreate is to dig a snowpit and look at the walls of your snowpit where these weak layers can be observed, and tested using various stability tests. Persistent slab avalanches can be triggered remotely and can propagate large distances. There are a lot of experienced avalanche practioners who will have nothing to do with steep slopes that contain buried persistent weak layers. Persistent slab avalanches are the cause of most avalanche fatalities, which is why we spend so much time monitoring the problem and talking about it. Please read Victor McNeil's recent observations about our persistent slab problem in the Blue mountains HERE.

    (2/24/2023)

    This photo was taken on a NNW facing slope at 7436' . The snowpack at this shaded and wind sheltered location was (a shallow) 4' deep. What is obvious in the photo are the weak layers of "sugar snow" or facets above and below the prominent crust a foot up from the ground. What you can't see in the photo is a layer of surface hoar that was buried by the 8" of new snow that fell at this location Tuesday afternoon through Thursday. Stability tests revealed weakness in the upper snowpack 8" down from the snow surface on this layer of buried surface hoar. An Extended Column Test I performed  failed on this layer of buried surface hoar using a moderate amount of force, no propagation was observed. Compression Tests failed on this persistent weak layer as well. Moderate force was needed to trigger failure. Shear quality was resistant but planar. I kept tapping on the column and was able to make the column fail on the 16th tap 32" down from the snow surface. The weak layer consisted of rounding facets just above the prominent crust. Shear quality was Q1 or sudden collapse on that layer. The take home message is that we have potentially dangerous buried persistent weak layers in our snowpack. I have been observing these layers at and below treeline on shady aspects protected from the wind where the snowpack is less than 4.5' in depth. This persistent slab problem is present and being observed in the Wallowas, Elkhorns, and Blues.

    Photo: TG

Avalanche Discussion

As temperatures rise, be mindful of staying well back from cornice edges today. Warming temperatures could dramatically weaken fresh cornices, causing them to fail under the weight of a human.

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