* WHAT...For the first Heat Advisory, heat index values up to 106. For the second Heat Advisory, heat index values up to 107 expected. * WHERE...Portions of northwest, southwest, and western Oklahoma and northern Texas. * WHEN...For the first Heat Advisory, until 8 PM CDT this evening. For the second Heat Advisory, from 11 AM to 8 PM CDT Wednesday. * IMPACTS...Hot temperatures and high humidity may cause heat illnesses.