There is as much as a low to medium (20-40%) chance of showers and thunderstorms, mainly across the Rio Grande Plains and the Northern Ranchlands, capable of producing heavy rain today into late tonight. There is a medium (40-70%) chance of showers and thunderstorms on Thursday, leading to a Marginal Risk (Level 1 of 4) of excessive rainfall across all of Deep South Texas. Isolated flash flooding or ponding on the roadways are possible.