(12:00PM – Mon, March 26th) A winter storm impacted portions of the state with up to around a foot of snow just two days ago, but it is spring, meaning conditions are ever changing. A new storm system pushing across the region the next three days will be affecting the state; bringing rain, thunderstorms, and the risk of flooding.
Things will kick off with periods of rain and thunderstorms expected across much of the state today and tonight (Mon/Mon Night). While Northern Illinois will likely dry out for Tuesday, periods of rain and thunderstorms will continue to be likely across much of Central and Southern Illinois. By Wednesday, Central Illinois will join Northern Illinois with dry conditions, while periods of showers and thunderstorms will remain likely across portions of Southern Illinois.
A strong low level jet(LLJ) in excess of 50kts will feed moisture into the region, with precipitable water values (PWATS) in excess of 1.00″ by tonight across much of the state, with values in excess 1.50″ nosing into the St. Louis area for a time. This will set the stage for the expected periods of heavy rainfall and thunderstorms across the state. With the best moisture feed and LLJ nosing into the St. Louis area and adjacent areas of Central/Southern Illinois, some training will be likely across this area, which will create flooding potential. The best flood potential will be in this area of Central/Southern Illinois Minor flood concerns will also be possible for areas that received several inches of snow, which has been melting, with expected rainfall on top of that.
Rainfall totals for this three day period will likely remain at less that 1.00″ for Northern Illinois, and in excess of 1.00″ for much of Central and Southern Illinois. An axis of 2-5″ of rain islikely in the vicinity of the I-70 corridor, from St. Louis to Terre Haute, IN.