A Flood Watch will go into effect late tonight for the entire area and last until Sunday morning.
Rainfall totals are expected to be between 2 and 4 inches for most of the region.
"The majority of this rain will happen in an 18-hour window of time, from Saturday midday through sunrise Sunday," said Storm Center 7 Meteorologist Rich Wirdzek. "Flooding chances will increase sharply from Saturday evening into the overnight.
Much of the snow melted Thursday as temperatures reached 40 degrees. The rain and snow melt will sit on top of the still frozen ground causing standing water. River levels are expected to rise, and flooding issues could persist into Tuesday, said Chief Meteorologist Jamie Simpson.
Light scattered rain showers will keep roads wet today Wirdzek said. It will be breezy and mild with highs will be in the mid-50s. Periods of rain are expected tonight with lows in the mid to upper 40s.
Rain will become steadier and heavier into Saturday afternoon with highs in the mid-50s. The rain is expected to stop around sunrise on Sunday.
Temperatures will be in the 20s Monday, and water on the ground could start to freeze.
Christmas Eve will be sunny, but chilly. Lows will be in the teens with a high in the upper 20s.
Christmas is expected to be partly cloudy with afternoon temperatures in the mid-30s.