SAN ANTONIO, Texas (Reuters) - Heavy rains inundated many parts of Texas on Saturday, triggering flash floods, forcing evacuations in at least one county and stranding drivers in the central part of the state, officials said.
One man was missing in San Antonio after being swept into a drainage ditch by flood waters as he walked his dog early Saturday, officials said.
A Union Pacific freight train derailed in Navarro County, south of Dallas, as an overflowing creek swamped the tracks. The derailment left locomotives and some rail cars on their sides, according to a company spokesman and TV footage. There were no reported injuries.[L1N12O0CQ]
The rainfall, up to 20 inches (50 cm) in little more than a day in the Dallas-area town of Powell according to one report, led to the cancellation of dozens of flights at Dallas/Fort Worth International Airport.
The precipitation was expected to intensify over the weekend as moisture from tropical depression Patricia, which struck the Pacific coast of Mexico on Friday as a very powerful hurricane, meets with a storm system coming from the west and over Texas.
Central, western and northern regions of the state were drenched in the last 24 hours with between 5 inches (13 cm) and 6 inches (15 cm) of rain, authorities said in a statement on Saturday morning.
Some parts of the Texas Hill Country in the central part of the state, known to weather officials as Flash Flood Alley for its flood-prone conditions, received 8 inches (20 cm) in eight hours Saturday.
Many parts of the state could see more than 8 inches (20 cm) of rain over the weekend, said the statement from the Texas Division of Emergency Management.
The Navarro County Office of Emergency Management said in a tweet it had reports of up to 20 inches (50 cm) of rain in the area, about 50 miles (80 km) south of Dallas. The town of Powell in Navarro County received 20 inches of rain in the past 30 hours, according to meteorologist Brett Rathbun of Accuweather.
By Saturday morning, flash flood watches and warnings covered every major population center in Texas, an area in which millions of people live.
Cities in southeast Texas near the Gulf of Mexico, including flood-prone Houston, were bracing for rain totals up to 20 inches (50 cm) starting in the early afternoon. Weather authorities said a coastal flood watches and warnings will be in effect for most of the day on Sunday.
Authorities in Navarro County requested sandbags for an unspecified number of homes that were being evacuated due to flooding, the statement said.
Interstate 45 in Navarro County was shut down in some spots due to rising waters, stranding some drivers.
Flash flooding in that county tipped part of a Union Pacific train carrying cement on to its side, and two crew members operating the train swam to safety, Jeff DeGraff, a Union Pacific Railroad spokesman, told CNN.
About 100 flights were canceled on Saturday at Dallas/Fort Worth International Airport, one of the country's busiest air hubs, according to tracking service FlightAware.
Dozens of streets were blocked with barricades in San Antonio due to high water, according to the city's Emergency Operations Center.
The man who is missing fell into flood waters and disappeared while walking with his girlfriend and a dog.
"His girlfriend said she saw him go underwater and then she lost sight of him," said Christian Bove of the San Antonio Fire Department.
Heavy rain also flooded streets in parts of the state capital, Austin, which has a population of about 910,000.
Additional reporting by Alex Dobuzinskis in Los Angeles and Karen Brooks in Austin; Editing by Frank McGurty and Cynthia Osterman