With more storms expected to slam Northern California later this week, officials worked frantically Monday to drain water from brimming Lake Oroville in hopes of heading off a potentially catastrophic flood. The operators at America’s tallest dam found themselves in a precarious position Monday, with both of the spillways used to release water compromised and the reservoir still filled almost to capacity after a winter of record rain and snow. Meanwhile, tens of thousands of evacuated residents downstream of the dam still have no clear word when they can return home.