Light showers will be possible Tuesday evening across Whiteside, Ogle, Lee and DeKalb counties. Most of the rain will be light and should remain under a tenth of an inch.
A better chance for more widespread rainfall arrives early Wednesday morning as warmer air moves into northern Illinois and southern Wisconsin, becoming a little more steady mid to late morning. A break in some of the activity is expected early in the afternoon as a surface warm front begins to shift north from central Illinois.
North of the front temperatures will be in the 50s but south of the front temperatures will have warmed into the 70s, possibly close to 80 degrees. The northward advancing warm front will be a result of low pressure moving into Iowa by Wednesday evening.
Instability will slowly increase as well and this could lead to a few stronger thunderstorms late Wednesday afternoon and evening over northwest Illinois and eastern Iowa. Should any storms develop, gusty winds would be the primary concern, however, a few isolated tornadoes can’t be ruled out (especially near the warm front).
Heavy rainfall will become a concern over parts of Iowa, Wisconsin and northwest Illinois where anywhere from one to two inches of rain could be possible. Showers and a few thunderstorms will be possible Thursday ahead of a cold front that will bring a little more dry air to the Stateline by Thursday night.