IOWA -- A heavy rain pattern is setting up for parts of Central Iowa beginning early Tuesday and continuing through Wednesday. A Flash Flood Watch will go into effect beginning at 10 PM Monday and last through Wednesday morning.
Numerous rounds of heavy rain fall are expected to move through parts of Western, Northwestern and Northern Iowa during the next few days. Iowa has already seen more than average rainfall amounts for the month of September so the already saturated ground in combination with more heavy rainfall will lead to increase run-off and increased threat of flash flooding.
The risk of severe storms is marginal. There may be isolated severe storms with this weather system.
Widespread 1 to 3 inches of rain is expected with some locally higher amounts above 4 inches through early Wednesday morning. Rainfall rates may even be intense at 1 to 2 inches per hour with some storms.
Central Iowa is stuck in between an strong area of high pressure over the southeastern US and a deep upper low across the western US and Rockies. Because of that strong moisture transport out of the southwest US, aided by moisture being pulled north for Tropical Storm Narda entering the Gulf of California, will feed the development of heavy rain through Iowa Tuesday through Wednesday morning. We have unusually high moisture values for late September and early October (two of our typically driest months of the year). Energy will lift up and around from the base of the trough through the Rockies and interact with the tropical moisture helping to fire up the storms and heavy rain. Training of storm cells moving over the same locations is expected as they will move parallel to the boundary.
Low lying areas and roads may become blocked with water. Small streams may rise rapidly. Ponding of water on poor draining streets and in fields is expected.
A flash flood watch means that conditions may develop that lead to flash flooding. Flash flooding can become very dangerous. Most weather related deaths are associated with flash flooding.