Flash Flood Watch Tonight/Monday forenoon for Western portion of the Chicago area
The Chicago National Weather Service Forecast Office has issued a Flash Flood Watch for potentially flood-producing rains tonight and Monday forenoon over western portions of our area and farther west to the Mississippi River (dark-green-shaded counties on the headlined map). Strongest storms with greatest rainfall look like for the most part they will occur in the area west of the Fox River – this includes Winnebago, Boone, Ogle, Lee, DeKalb and LaSalle Counties. Localized flood-producing downpours could occur in other portions of the Chicago area as well.
As low pressure deepens in the central plains and the associated warm front moves north over our area, widespread showers and thunderstorms are expected to develop and move from southwest to northeast across central and northern Illinois tonight and early Monday. Heaviest downpours are expected over the western half of Illinois. Heavy 1 to 2-inch-plus rains may fall over saturated soils with rapid runoff into swollen streams and the Rock and Pecatonica Rivers already forecast to incur moderate flooding. The Fox and Des Plaines Rivers currently in flood could also be impacted by the overnight/early Monday rainfall.