Weather Alert Response and Notification Act or the WARN Act This bill directs the Government Accountability Office (GAO) to study the effectiveness of local, state, and federal alerting systems in disseminating timely and relevant information during weather-related emergencies. In conducting the study, the GAO must (1) evaluate the efficacy of various alert mediums, including platforms such as social media; (2) assess the guidance and training for developing alert content; and (3) determine whether improvements could be made to public alerting based on input from a sample of emergency managers, local officials, and community groups.