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backcountry advice

BACKCOUNTRY ADVISORY As of Wednesday, March 17 Occasional periods of partly clear weather are starting to appear with a bit more regularity — a welcome change for everyone. Power flurries and weak systems have kept the old tracks well filled in. The sunshine has been great for the general mental health of the valley, but it has also created weak layers in the snowpack that are proving to be some of the most problematic of the season so far. A buried surface hoar layer that is sitting from 40cm to over 100cm below the surface is starting to become very reactive. It is most in evidence at treeline elevations, but can also be found in the higher alpine terrain. In some seemingly likely areas you may not find it at all — whether it didn't even form, or blew away in the wind, we'll never know. If you are covering lots of different terrain in your touring travels, take the time to dig numerous quick profiles. Can you find the surface hoar layer and are the crystals still quite obvious? A 5mm sized crystal will not settle out quickly. The layer may be initially easy to see on the pit wall, or it may only be found when you do some stability tests. If the layer is deeply buried and seemingly well bridged, it may require a larger trigger or a failing layer above that steps down. Be very cautious. The consequences of being caught in treed terrain may be fatal, regardless of your burial time. Solar aspects are starting to go through the melt-freeze cycle, and there have been reports of avalanches running on the resulting crusts. At this time of year, you can expect that any hint of even filtered sunshine will affect the surface snow on south facing slopes. If you begin to see snowballing happening, file it in your mind that a crust will probably form overnight and provide another good sliding surface. Travel with care. The weaknesses in the snowpack are not everywhere, but they are out there. Don't presume that a few sets of tracks guarantees a slope's stability, and be ready for drastic stability changes when you move through different aspects and elevations. It has been a frustrating touring season for most, but don't lose your sense of caution when the opportunity finally arises to put a good visibility trip together. The avalanche danger as of March 17 is rated as CONSIDERABLE. Check with your local ski patrol for current information or call the avalanche danger rating line at 938-7676.

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