Voters in Alberta may weigh in on a referendum later this year that would ask if they want the province to leave Canada. On Monday, Alberta separatists announced that they had officially turned in more than 300,000 signatures in support of putting the referendum on the ballot, surpassing the roughly 178,000 needed for a citizen-led petition.  The signatures still need to be verified by elections officials—and that process is on hold until a judge issues a decision in a legal challenge to the proposed measure. The Alberta separatist movement dates back decades , but has gained momentum in the past year, after the Liberal Party, led by Prime Minister Mark Carney, won Canada’s federal election. Here’s what to know about the proposed referendum. What would the proposed referendum ask voters?…