After days of urgent warnings, Tropical Storm Hilary made landfall in Baja California on Sunday, turning roads into rivers and imperiling homes before barreling north toward Southern California. By 6 p.m., the Southland was seeing flooding, downed trees, road closures and high winds. Forecasters with the National Weather Service in Las Vegas said conditions were continuing to deteriorate across parts of Southern California and western Nevada, especially the mountains and deserts. They said life-threatening, catastrophic flooding remained a possibility.