The big changes start to occur on Friday. A cold front will be moving in from the north & will pass by the evening hours. Ahead & along that front, there will be showers & thunderstorms, increasing in the evening hours. Coverage is going to jump to 30% on Friday. Some spots that see those storms will get some heavy rain, so keep that in mind. Lubbock will see a high of 90°, which will be the last 90° reading for several days.
Behind that cold front, high temperatures will drop down to 80° on Saturday & 82° on Sunday. You will need your rain gear on Saturday, because ample moisture will bring in more thunderstorms. Coverage will be 40% for Saturday. There will be pockets of heavy rain, so flooding is something that will occur across the area. So, be careful while driving. Sunday will see another round of scattered thunderstorms, with coverage up to 30%.