* WHAT...For the first Heat Advisory, heat index values up to 108. For the second Heat Advisory, heat index values up to 109 expected. * WHERE...Portions of southeast Arkansas, northeast Louisiana, and central, north central, northwest, south central, southwest, and west central Mississippi. * WHEN...For the first Heat Advisory, until 7 PM CDT this evening. For the second Heat Advisory, from noon to 7 PM CDT Wednesday. * IMPACTS...Hot temperatures and high humidity may cause heat illnesses.