IEM Daily Feature
Monday, 25 July 2022

Three Hour Flash Flood Guidance

Posted: 25 Jul 2022 05:30 AM

The NWS creates a grid product called Flash Flood Guidance. This guidance estimates the amount of rainfall needed over a given time period to produce non-urban flash flooding. This product is often informative to look at as it sometimes reverse mimics recent heavy rainfall events. Such heavy rainfall events lower the threshold needed for near term future events as near surface soil is saturated and subsequent rainfalls will have higher amounts run-off, which leads to flash flooding. The heaviest rainfall totals over the weekend were confided to far northeastern Iowa and you can see the lower threshold amounts there.

Good = 12
Bad = 0