The heavy rains is rather complicated because we have two areas merging into one area. The first area will come from the Upper Level low coming out of Texas. Because tropical moisture is getting thrown back into that upper low, we will see a swath of heavy rains from Western Texas into the Mississippi Valley. The second area will come after landfall from Zeta occurs that will move up from Louisiana into the Tennessee Valley where the areas of heavy rains will merge into one area that will go from the Tennessee Valley into the Mid-Atlantic. Due to the speed of Zeta after landfall, the rain will come quickly and cause flash flooding.
We have links in the severe weather tab that covers the rainfall and flooding potential.