Bollettino valanghe

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Wed
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In sintesi

Yesterday's strong winds built stiff slabs that will continue to be sensitive today. These slabs will generally be small and isolated but may be large enough to knock you off your feet or sled and send you downslope. Thanks to the strength of the wind, you may find these slabs in unusual locations. Be alert to the consequences of being caught in an avalanche in the terrain you are traveling in.

Problemi valanghivi

  • Wind Slabs

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    1

    Very strong winds re-sculpted the snowpack in this zone yesterday. In many areas, it scoured down to old surfaces and blasted whatever snow it could pick up off into the atmosphere. In other locations, it deposited stiff, densely-packed drifts and slabs. On Galena Peak (observation here), I found that the wind had been doing a lot more scouring than loading, and I elected to avoid steep terrain where new slabs existed. 

    Major wind events transport snow in atypical ways. Many of the spots that normally host wind slabs have been scoured down to stiff, icy crusts. Instead, you might be finding slabs a bit further down from ridgelines on mid-slope terrain features. Recent slabs are sitting on a variety of surfaces, including slick crusts, facets, or some combination of these. These interfaces can take some time to heal and the cold temperatures aren't helping. Today's slabs are unlikely to be large enough to bury you, but they will definitely be big enough to take you off your feet and send you downslope. Be alert to the consequences of encountering a slab in the terrain that you are traveling in. 

    (3/27/2021) Skiers on Titus Ridge yesterday triggered two wind slab avalanches in steep terrain.

Avalanche Discussion

BAD RIDING or a GOOD LEARNING OPPORTUNITY?

I'm a diehard optimist. I think that backcountry skiing is one of the things that has made me this way. After all, it's not always soft, deep powder out there. If you head into the backcountry today, you can expect to find a wide variety of challenging surface conditions. The combination of warm temperatures and strong sun over the past few weeks, an impressive wind event yesterday, and well below freezing temperatures last night have left us with a lot of firm, icy surfaces to play on. There are isolated pockets of soft snow out there, but they are few and far between. Fortunately, the snow-covered mountain environment provides us with endless opportunities to observe and learn, even when riding conditions aren't great.

The snowpack is in a constant state of change and each day is a snapshot in this process. In the backcountry today you'll get a good lesson in the power of the wind to reshape a snowpack overnight. As you move through the mountains, take the time to observe the nature of the snow you are traveling through. Make an educated guess why the snow you are moving through feels and looks like it does. Look for areas where the wind has scoured down and revealed old ski and sled tracks underneath. Think about the amount of force required to do this and where this snow might have gone. Keep your eyes peeled for areas where these scoured surfaces are covered by smoother, dense drifts. These are likely new wind deposits, exactly the problem you are looking to avoid today. This process of observation is one of the most powerful tools in our safe backcountry travel in our toolkit. It is also what enables us to sniff out areas with good, stable skiing and riding.

Here's an interesting feature of the snow for you to focus some of your attention on today: yesterday, as I skied up and down Galena Peak, I noticed a dirty/dusty layer near the surface of the snow. The extreme SW winds that blew overnight on Sunday picked this dust up in the Snake River Plain (perhaps?) and dropped it as it traveled along. Layers of dust like this can have a couple of impacts on the snowpack. Since the dust is darker than the snow, it decreases the reflectivity of the snow surface (a property known as "albedo") and allows for more solar radiation to be absorbed. This can increase the rate that the snowpack melts and can negatively affect the developing corn cycle. I know, I'm just full of good news this morning. Be on the lookout for this dusty layer and use it to help you identify the timing of slab formation. If you are seeing clean slabs that sit on this dusty layer you can be sure that the slabs you are looking at are fresh. Neat! Take some time to mentally map out where you are seeing this dusty snow and areas where it seems to be less prominent. It just might help you find better corn skiing later in April. Also neat! As I said, I'm a diehard optimist. There is always something new in the world of the snow, we just have to choose to look.

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