Portions of the Southern Plains on Tuesday morning were beginning to feel the force of the thunderstorms and flash flooding that is expected to hit the region over the next few days.

National Weather Service radar showed rain falling across Texas and Oklahoma, the beginning of a series of thunderstorms forecast to bring up to 10 inches of rain to the South by Thursday.

The service said the thunderstorms could also generate tornadoes, and its Storm Prediction Center had already received one report of a funnel cloud in Texas by 10 a.m. Central Time.

A tornado watch was in effect for 31 counties in Texas. It was set to expire at 1 p.m. today.

Other counties in the Dallas-Fort Worth area were under warnings and watches for severe thunderstorms, and the service advised high wind gusts and penny-sized hail were possible.

The National Weather Service also expanded its flash flood watches to larger parts of Texas, Oklahoma, Arkansas and Louisiana, warning waters could rise quickly in those areas. The highest rainfall totals are still expected in East Texas, Western Louisiana and Southwest Arkansas, but updated forecasts show parts of Missouri and Oklahoma could receive 4 inches.

Many of the flash flood watches are slated to begin this afternoon and continue through Thursday, though residents of the affected areas should monitor their local forecasts.

The service’s Storm Prediction Center said communities in South Texas, as well as those along the state’s Gulf Coast, had the highest risk of experiencing severe thunderstorms today. It said there was an “enhanced” risk of the storms in those areas, the middle level on a five-tier system.

But the tornado was reported in Tolar, which is located about 80 miles southwest of Dallas.

The Storm Prediction Center had received at least 10 reports of high winds as of 10 a.m. Central Time, all in North Texas. The reports indicated that gusts of up to 70 mph were recorded in Tarrant County, where a roof was blown off a business and large branches fell on a sidewalk.

Utility company Oncor said about 36,000 of its customers in the Dallas-Fort Worth area were without power as of 10 a.m. Tuesday. And flight monitoring website flightaware.com said some 230 flights to or from Dallas-Fort Worth International Airport had been delayed by that time.