With a warm humid rather unstable air mass in place – dew-points in the upper 60s and lower 70s and under a weak upper low-pressure system centered generally over downstate Illinois, conditions are ripe for scattered showers to develop over northeast Illinois and northwest Indiana as heating progresses and a lake breeze front develops .
Indications are that the greatest showers/t-storm coverage will occur in central and southern Illinois/Indiana with more widely scattered showers up our way. Minor disturbances will pinwheel around the low pressure and set off a few bands of showers, and the movement of the lake breeze inland could also act as a “trigger’. So watch for showers developing late morning into the afternoon, generally forming in north-south bands. Showers will be slow-moving and there could be significant rainfall due to the longer duration. Thunder is possible in some of the stronger storm cells, but the probability is only about 10% for any given location, with a much higher probability of showers hitting a given point.
Most convective activity should diminish as we head toward evening and the overnight hours.