Severe thunderstorms and flash flooding threaten Southern Plains, Midwest, Great Lakes

A new round of severe thunderstorms was expected to sweep across the Southern Plains, Mississippi Valley and Great Lakes, with flash flooding carrying the greater danger in places where rain could fall after sunset and overwhelm streets, drains and low-lying neighborhoods.

The Weather Prediction Center said a strong cold front pushing south through the Plains was the main trigger for a line of storms capable of producing very heavy rain. Near the Gulf Coast and lower Mississippi Valley, precipitable water values were expected to climb to between 1.5 and 1.75 inches Saturday evening, a setup that raised the risk of intense downpours in a narrow window of time.

Forecasters highlighted Houston, Beaumont and Alexandria as especially vulnerable because much of the convection was expected at or after sunset. That timing matters: rain falling after dark is harder for drivers to see and harder for emergency crews to track as water rises quickly in urban areas. The Weather Prediction Center also placed a marginal risk of excessive rainfall over portions of the Gulf Coast and Lower Mississippi Valley in its Day 2 outlook.

The Great Lakes faced a different but related problem. Rain there was expected to add to ongoing flooding rather than simply start new problems, with repeated rounds of storms threatening to keep waterways high and saturated ground from recovering. The Weather Prediction Center’s short-range discussion also pointed to additional rounds of strong to severe thunderstorms with heavy rain across the Upper Midwest and the Great Lakes.

The region had already been hit hard. Guy Carpenter said storms from April 13 through April 15 affected a broad corridor from the Plains into the Lower Great Lakes, producing widespread hail of 2 inches or larger, localized hail of 2.5 to 3 inches, and isolated reports above 3 inches in eastern Iowa, southern Wisconsin and northern Illinois. The firm said the Upper Midwest and Great Lakes had also seen a record-fast start to the thunderstorm season, with record rainfall around Lake Michigan over the last 30 days driving major flood-stage reports in Wisconsin and Michigan and numerous basement-flooding complaints.

National Weather Service offices in Amarillo, Dodge City and Bismarck carried the same severe-thunderstorm and flash-flooding message, underscoring how broad the risk remained across the central United States as the cold front moved through.