A low-pressure system brought snow in the Sierra along with saturating showers and threats of tornados to the Sierra foothills Monday. A tornado warning was issued for southwestern Nevada County by the National Weather Service, beginning at 3:37 p.m. and continuing until 5:45 p.m., said Karl Swanberg, forecaster with the National Weather Service. At about 5 p.m., the weather service reported a severe thunderstorm capable of producing a tornado about seven miles west of Lake of the Pines, moving northeast at 25 mph. The storm’s path included Lake of the Pines, Alta Sierra, Cedar Ridge, Grass Valley and Colfax, the …