All the ingredients are in place for big rain totals across the state over the next couple of days. Wednesday we will be looking downstream (to our west) for severe weather potential. The risk shifts to Indianapolis for Thursday night and Friday morning. Thursday’s risk area includes a moderate risk for Memphis, Little Rock, St. Louis and Springfield, MO. Tornadoes and hail will be possible in those communities Thursday afternoon into the early evening hours. These strong storms will likely turn into heavy rain producers by the time they make it to us on Friday morning. They will keep us busy with flooding likely as people are making their way into work on Friday morning.
So why are we expecting all this rain? We should see high pressure to our south setting up in the eastern Gulf of Mexico. This is forcing the subtropical jet stream into the Midwestern states. This slow moving boundary is on top of us this morning and is the reason we are already seeing rain. This rain will continue off and on throughout the day today. We will also see off and on rain on Thursday as we await the stronger storms.
Meanwhile to our north a trough of colder air is being driven south. This air, along the polar jet, along with the Subtropical Jetstream will join together to create large areas of instability, favorable upper wind dynamics, convergence at the surface and large lapse rates. As the system moves to the east, severe storms and heavy rain will be possible. This will especially be likely for areas in southern Indiana and parts south. This will likely include places like Nashville, Louisville and Evansville.
For us the timing of the system points to heavy rain, strong straight line winds, and flooding as the key concerns. At this point it looks like Friday around midnight will be the most likely time for heavy rain but this will only be the peak time. We could potentially see upwards of 2 inches of rain Through Thursday night in some areas. We could then see a quick burst of upwards of two inches in some parts of the state overnight on Friday before the rain finally pushes east as the sun is coming up on Friday morning. All in all, I would not be surprises if one or two communities record more than five inches of rain! Clearly that much rain would set off areal flood warnings across the state.
Temperatures today will be around 60 degrees with rain around through the day. Thursday looks to be slightly warmer even with our rain chances sticking around and the chance for severe weather Thursday night.