Scattered showers and thunderstorms will continue Wednesday night, increasing in coverage during the overnight. So far, the storms have remained below severe limits but there still remains the small risk of a strong storm or two capable of producing penny to quarter sized hail overnight.
Pockets of heavy rain will also occur through the night with totals adding up to around an inch in some locations. Areas that see repeated rounds of rain may also experience localized flooding, but the overall flooding risk remains low.
The rain will begin to weaken as it lifts north through Thursday morning. This is the result of the low-level jet weakening by sunrise. There will still be some showers that continue near the state line throughout the day, and even some scattered rain activity elsewhere, but Thursday afternoon should remain mostly dry. As the low-level jet picks back up again Thursday night, rain and thunderstorms will develop west of the Mississippi River. These will shift east into Illinois Friday morning as a deepening low-pressure system moves towards northern Illinois. Another round of heavy rain and thunderstorms can then be expected mid to late morning Friday, into Friday afternoon where an additional 1-2 inches of rain may fall. Between Wednesday night and Friday night rainfall totals will add up between 1-3 inches.
There is also a low-end risk for strong to severe storms during the afternoon and evening Friday. A marginal risk for severe weather is in place for all of northern Illinois and some of southern Wisconsin. Increasing instability within the warm sector of the storm system, south of the warm front and east of the cold front, will help fuel a few severe storms during that time. The Stateline remains on the northern fringe of that risk, just north of the warm front. This puts us at a lower risk for severe weather, but still close enough to monitor. If storms were to turn severe, damaging winds would be the biggest threat. But with the close proximity of low pressure (increasing wind shear in the atmosphere) a small tornado risk would be present.
Scattered showers will continue on the backside of low-pressure Saturday as winds shift to the northwest, gusting to 45 mph into the afternoon. It’ll be an overall raw and brisk October afternoon with highs in the low 50s, but wind chills in the 40s.