* WHAT...For the Heat Advisory on Thursday, heat index values up to 105. For the Heat Advisory on Friday, heat index values up to 108 expected. * WHERE...Portions of central, east central, southeast, southern, and southwest Oklahoma and northern Texas. * WHEN...For the Heat Advisory on Thursday, until 8 PM CDT this evening. For the Heat Advisory on Friday, from noon to 8 PM CDT Friday. * IMPACTS...Hot temperatures and high humidity may cause heat illnesses.