(10:00PM - 10/25/19) The combination of Tropical Storm Olga and a storm system merging across the region will bring heavy rain, flooding and windy conditions to portions of the state this weekend.
As mentioned in our initial discussion this afternoon...A disturbance and associated storm system is currently pushing across the Southern Plains and Southern Mississippi Valley. Additionally, newly formed Tropical Storm Olga is currently racing northward across the Gulf of Mexico and towards the Louisiana coast. The storm system and Tropical Storm Olga are expected to phase together tonight and into tomorrow. The outcome from this will be a well organized storm system, which will lift northward from the Gulf Coast, tracking up across Illinois and Indiana on Saturday.
High moisture content characterized by PWAT's of 1.00-1.90" will be pulled northward and into the region, courtesy of Tropical Storm Olga. This will lead to heavy and efficient rainfall, with widespread rainfall totals of 1-3" likely across much of the state...the exception being Western and Northwest Illinois, where rainfall totals will remain well below 1.00". Locally higher amounts of 3-5" will be possible across portions of Southern Illinois. The heavy rain and expected high rainfall totals will likely lead to minor to moderate flood potential for some areas, with Southern Illinois being at greatest risk for this for flooding.
Windy conditions are likely across the state as well, as the storm system becomes more organized and strengthens after the aforementioned phasing of systems occurs. Wind gusts of 20-40MPH are likely across the state Saturday morning through early Sunday morning. Isolated higher wind gusts of 40-50MPH will be possible across Southeast and Eastern Illinois during this period as well.
Below is the TAM flood and wind forecasts for late tonight-early Sunday morning.