FLASH FLOODING

On today's storm map, the biggest concern is flooding across the Midwest and Ohio Valley, with the threat shifting into the eastern Ohio Valley and Mid-Atlantic states tomorrow.

Another round of thunderstorms will bring several inches of rainfall to some locations, adding to what has already been a very wet stretch of weather. With soils saturated and streams and creeks already running high, it will not take much additional rainfall to produce significant flash flooding.

The flooding could take several forms, including street and urban flooding, rapidly rising creeks and streams, and smaller waterways overflowing their banks. Areas that experience repeated thunderstorms could see particularly serious problems as rainfall accumulates faster than the ground and drainage systems can absorb it.

The flooding will not necessarily end when the thunderstorms move away. Water from the smaller streams and tributaries will eventually drain into the larger river systems, meaning major rivers such as the Ohio River could begin rising into next week.

This creates a prolonged hydrologic concern: even after the heaviest thunderstorms end, river levels may continue to increase as runoff works downstream.

Overall, this is shaping up to be another difficult period for the Midwest and Ohio Valley, with flash flooding first and rising river levels later. Residents in flood-prone areas should remain prepared for rapidly changing conditions, particularly where additional thunderstorms repeatedly cross areas that have already received substantial rainfall.