The National Weather Service has flood warnings in effect for the Mississippi River and in central Iowa for the North Raccoon River at Perry. Forecaster Jeremy Graham says the warning includes a prediction that the Raccoon will continue to rise for two more days. He says it should go above “moderate” flooding Saturday afternoon and they expect a crest Sunday morning — the official flood stage is around thirteen feet, it’s already at 14, and the expected crest on Sunday should be almost 18 feet deep. Grahams says several factors go into a flood prediction that can extend several days into the future. Automatic gauges all up and down the rivers give readings, and there are models of the land’s topography that help show what happens when rain falls in a river basin and upstream, all things that help forecast how high a river will crest and when it’ll happen. Current warnings take into account the fact that the rivers are already over flood stage, the rain that’s fallen upstream, and rain forecast to fall in the next few days. A week or more of intermittent rain has several rivers at or above bank-full in Iowa. Some are for tributaries like the Rock River that flows into the Mississippi at Moline, and on the Mississippi itself many areas are over flood stage and have warnings, from Dubuque down to Keokuk. Grahams says the fears of drought this year are mostly finished with the most recent rains. In Des Moines, rainfall’s about six inches above normal, and going into the year there was a 20-inch deficit so while it’ll take longterm rains for a recovery we’re closer to normal. Meanwhile, not much more rain is forecast throughout the weekend, so while flood warnings remain for the Mississippi and Raccoon, he doesn’t expect any more to be added to the list.
