SHAVER LAKE -- In a pounding rain, scientist Matt Meadows skis toward a cluster of snow sensors. The temperature dips, rain turns to sleet, then snow. This is a freezing, soggy, miserable place. But it's the perfect setting for Meadows and other snowpack researchers. Southeast of Shaver Lake at 6,000 feet in the Sierra, storms switch back and forth between rain and snow -- it's called the rain-snow transition zone.