Because of this, precipitable water values will be greater than 200% above normal in many parts of the MS and OH Valleys, as well as the Great Lakes. All convective and stratiform precipitation will be highly efficient at producing rainfall. Average QPF from the models across these regions is forecast to be between 1-2 inches, with many locations possibly seeing 3-4" because of the tropical nature of the atmosphere. Even if the Gulf had not opened up (which it has) rain would still be heavy because of the connection. The only thing that may impede the heavy rain threat to the north will be strong convection across TX OK and LA. If very deep convection can rob moisture transport, many areas may see an inch at most with spotty 2" amounts. For now I believe many areas will see 1-3" with spotty 4" amounts where convection trains.
Once the upper low swings further to the north and east, many areas of the MS and OH Valleys, as well as the Lakes States, will be in the right rear quad of the upper jet. This will act to enhance vertical motion and divergence above the precip, only acting to increase the amount of rainfall. Below is the Eta 250 mb forecast as of 06Z tonight - notice the very powerful 130 kt jet! I hope flash flooding doesn't keep people away from the polls tomorrow.
