Rain chances will increase sharply late Thursday, especially over central and southern Iowa. It will be the most significant rain folks in those areas have seen for quite some time, and locally heavy rains, and amounts of 1 inch or more possible in some areas by the time the precipitation ends Friday morning, with localized ponding/river rises possible. A few non-severe thunderstorms are even possible. There is also the potential for some localized snowfall early Friday as well. Temperatures may cool and approach the freezing mark in spots overnight night Thursday into early Friday morning, which could result in some areas flipping to snow. Whether this will occur, where it would occur, and how much snow is possible all remain uncertain at this time, and are dependent on the degree of cooling and its duration. If you have travel plans over southern Iowa Thursday night or Friday, it would be best to monitor the forecast into tomorrow when more details on heavy rainfall/snow potential may be available.