Bollettino valanghe

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Wallowa Avalanche Center
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3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

 Triggering an avalanche on steep east and southeast facing terrain at and near ridgelines is likely today because of windslab formation on that leeward facing terrain. Cautious route finding and conservative decision making will be essential for safe travel on the aforementioned terrain. Heightened avalanche danger exists on all other terrain steeper than 35 degrees. Evaluate snow and terrain carefully on all terrain steeper than 35 degrees today.

Problemi valanghivi

  • Wind Slabs

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

    This storm cycle that began January 31 has brought 10"-16" of new snow to our mountains. This new snow has been  accompanied by west and northwest winds strong enough to transport snow and form windslabs on leeward east and southeast facing terrain. Expect to find thick and sensitive wind slabs at and near ridgelines on east and southeast facing terrain. These windslabs are precariously perched on top of, and poorly bonded to, weathered and crusty snow surfaces. While traveling throughout the mountains today and tomorrow, keep an eye out for windslabs that might be present on terrain you plan to travel through. Windslabs look like large dome like  pillows and often sound hollow or drum like  when traveled upon. Also, the observance of shooting cracks projecting out from your snowmobile, skis, snowboard, snowshoes etc. is a glaring red flag that the snow you are traveling across is unstable and could avalanche. When traveling on leeward facing terrain steeper than 35 degrees, particularly near ridgelines, cautious route finding and conservative decision making will be essential. Triggering an avalanche on this  afformentioned  terrain is very possible. And of course, keep an out for natural avalanches that may have occurred during this recent weather cycle. The observance of natural avalanches is the most obvious red flag that the snow is unstable.

  • Loose Dry

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    About 12" of loose dry snow has been observed in our mountain region during this most recent storm cycle. This snow is sitting on top of firm crusts in most areas. In shady wind sheltered locations below treeline this snow also rests upon uncohesive/weak facets and surface hoar that was present before the arrival of the new snow. It will be possible to trigger an avalanche on terrain steeper than 35 degrees where this loose dry snow exists, which is most areas below treeline. Heightened avalanche danger exists today on all terrain steeper than 35 degrees. Evaluate snow and terrain carefully before committing to this terrain. Keep in mind the consequences of getting caught and  knocked off your feet or sled, then carried into trees or gullies. The loose dry avalanche might seem relatively benign but the consequences of getting caught in one could be severe.

Avalanche Discussion

During this recent storm cycle I personally have observed between 10"-15" of new snow since Monday morning while ski touring in the Western Wallowas. Judging by observations I have received from other recreationalists, similar storm totals exist throughout our mountain forecast zone. Although I have not seen or experienced instability in my travels, and I have not heard of any remarkable instability problems, I have been moving through the mountains cautiously the last two days and plan to remain cautious. The presence of numerous red flags like recent heavy snowfall, wind transported snow, persistent (weak) grain types in the upper snowpack, persistent grain types at the new snow/old snow interface, and weak snow structure in the top 2' of the snowpack give me plenty of reasons to stay off of slopes steeper than 35 degrees for now and the foreseeable future.  Like I stated above, I have not personally observed avalanches but suspect it very possible to trigger one so am stepping back and keeping my slope angle below 35 degrees. We continue to see poor snowpack structure in the form of crusts and facets (sugar snow) that are now buried under approximately 10"-16" of snow depending on location. These buried weak layers could remain a problem for quite some time into the future. The more snow we receive going forward, the more weight and therefore stress we are putting on these weak layers. Recent snowpack data reveals weakness at these crust facet layers now buried a foot or more in the snowpack. My column test from yesterday in the Western Wallowas exhibited propagation 16" below the snow surface on a north facing slope at 8000' . My ski partner did not see propagation in his columns, but his compression tests were failing on the same layer and were sudden and planar. The weak layer in my ECT column test was a1" thick layer of sugar snow below a 1" thick crust. This same crust/facet combo was observed in the Flagstaff Butte area yesterday by an observer. His observations were gathered in a location around 6000' in elevation. The take home from this data is this now buried persistent weak layer is present at low elevation and high elevation areas throughout our forecast region wherever the crust layers are present. We are thoroughly monitoring this condition and will keep you abreast of what we find out there. And please, let us know what you are finding out there by posting your observations. We look forward to seeing you at The Wallowa Avalanche Center Backcountry Festival this coming weekend at Anthony Lakes Ski Area. Find details on the W.A.C. homepage.

Forecast presented  by @onxbackcountry.  onX Backcountry is a GPS navigation and mapping tool designed with your backcountry objectives in mind, equipped with Avalanche Forecast and Slope Angle layers, Offline Maps and more.

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