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Watch the Weather | Study the Snowpack
Travel Safe in Avy Terrain
Avalanches are most common during the 24 hours following a 12-plus-inch snowfall, and the more it dumps, the higher the risk. Be especially wary of heavy, wet snow on top of a powdery layer (sometimes called an upside-down storm).
Wait at least a day before hitting new snow after a shower. The 24 hours immediately following rain are especially dangerous. Tiny-grained fresh flakes soak up water, reducing stability. Older snow has better drainage—thanks to regular freeze-thaw cycles—so rain percolates through, making the snowpack less likely to shift.
Freeze-thaw patterns are more important than the current temperature. When it’s above freezing for more than 24 hours, or the mercury never dips below 15°F, slides are more likely. Also, quick shifts (a rise of more than 15 degrees in 12 hours) destabilize snow, while a slow rise is generally stabilizing.
Steady winds load existing snowpack with extra weight; wind alone can deposit snow as much as 10 times faster than snowfall. The leeward side of peaks and ridges collect slabby drifts, making them more avalanche-prone. Scoured and scalloped terrain—which indicates that snow has been blown away—is safer than rounded, airy-looking pillows of snow.