Watch out for the brown snow | AspenTimes.com
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Watch out for the brown snow

Catherine Lutz

If you’re going out into the backcountry, beware the brown snow. Seriously.On Feb. 15, a huge cloud of dust arose from the southwest (which has been bone-dry this winter), was carried to our fair valley by strong winds, and blanketed our pristine white snowpack. It created enough of a layer of dust that it is still visible if you cut 65 centimeters down. And because the dust is essentially a source of heat, it’s caused the layer above it to be unstable – already several avalanches have been attributed to the southwest dust.The dust layer “absolutely destroys the spring skiing,” said Brian McCall of the Roaring Fork Avalanche Center, during a presentation Monday night on avalanche safety and spring conditions that local nonprofit PowdertothePeople.org sponsored. McCall’s presentation summarized local conditions and weather and snow patterns since early February; this effort to understand what’s happened should help us understand what could happen with spring skiing – or not.Here’s a summary of McCall’s summary. Early February saw a similar pattern to what had been happening all season: small, frequent snowfall with mostly west to northwest winds. Then, on Valentine’s Day, the wind changed abruptly – since then most storms and all winds have come from southerly directions. A warm period ensued, with several nights above freezing, one rainy night on the last day of February, and daytime temperatures approaching 60 degrees – this was very bad for the stability of the snowpack. Since March 8, winter has returned, with snow every day so far except St. Patrick’s Day.But that doesn’t mean the snowpack has restabilized. Wet snow has added 4-6 inches of water to the snowpack, and crusts formed by sun and rain during the warm period contributed to prime conditions for wet slab avalanches. With strong winds still out of the south and southwest, there have been plenty of small avalanches on north through east aspects in the last couple of weeks, many of them running on the dust or crust layers.Unless the dust-crust layer gets buried, avalanche danger will remain in the moderate to considerable range. A quick warming like we’ve seen in recent years will be bad for spring skiing; if it warms up gradually, we can hope for plenty of turns for weeks to come.So pray for snow – a foot of it, every night.Avalanche reportBackcountry avalanche danger in the Roaring Fork Valley is moderate with pockets of considerable at and above treeline. Below treeline, avalanche danger is moderate. The continued presence of both natural and triggered avalanches in the backcountry means we will still have to pay close attention to the bond of some of the weak layers in our snowpack. Extra caution is still advisable for steeper wind-loaded terrain near and above treeline as the potential for triggered avalanches, and possibly some large ones, still exists.Avalanche danger details provided by the Roaring Fork Avalanche Center. For more information, call 920-1664 or visit http://www.rfavalanche.org. For conditions around the state, visit geosurvey.state.co.us/avalanche.


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