LOS ANGELES (AP) — Some residents stranded in Southern California mountain communities by a huge snowfall could be stuck for another week, an official said Friday. A late-February blast of arctic air produced a rare blizzard east of Los Angeles in the San Bernardino Mountains, where thousands of people live at high elevations in forest communities or visit for year-round recreation. Extraordinary snowfall buried homes and businesses, overwhelming the capability of snowplowing equipment geared toward ordinary storms. By last weekend, all highways leading up into the mountains were closed and have opened intermittently since then to residents and convoys of trucks loaded with food or other supplies. The estimate by…