The snow shovels may come out of hibernation this weekend, when cold fronts moving in from the north and south dump several inches of the white stuff across Boston and outlying areas. And state-contracted plow drivers are considering sitting the storm out. ``Saturday looks ugly,'' said Alan Dunham of the National Weather Service in Taunton. ``There's a possibility of more than 6 inches of snow. We don't expect the snow to clear up until Sunday morning.'' That could mean bad news for drivers if snow-plow operators in a contract dispute with the state refuse to show up when called to...