* Storm finally moving after stalling in Gulf of Mexico
* Torrential downpours threaten already flooded areas
* Obama calls Florida governor, offers federal help
By Michael Peltier
TALLAHASSEE, Fla., June 26 (Reuters) - Tropical Storm Debby weakened as it drifted slowly eastward over Florida on Tuesday and threatened to dump more rain on already flooded areas.
After stalling in the Gulf of Mexico, the storm was finally moving but was expected to take two more days to finish its wet slog across Florida.
"We will have sunshine for the weekend but a lot of wet ground," said Bryan Koon, director of the Florida Division of Emergency Management.
Nearly 20 inches (51 cm) of rain has fallen in two days on Wakulla County, a Gulf Coast county famed for its natural springs. Roads were under water in many parts of the surrounding "Big Bend" area where the Florida Panhandle meets the peninsula.
Parts of Interstate 10 were closed between the capital, Tallahassee, and the Atlantic coast city of Jacksonville. The storm left 29,000 people without power across the central and northern parts of the state, emergency managers said.
Forecasters at the National Hurricane Center said Debby could bring another 4 to 8 inches (10 to 20 cm) of rain and possibly tornadoes to north Florida and southeast Georgia in the next two days.
Debby's top winds weakened to 40 miles per hour (65 km per hour), just over the threshold to remain a tropical storm. It was expected to weaken further over the next two days as the center moved inland, but could strengthen back into a tropical storm as it crossed into the Atlantic Ocean, the forecasters said.
The center of circulation was still in the Gulf of Mexico, about 70 miles (110 km) west of Cedar Key, Florida. But Debby was a large and ragged storm and most of the thunderstorms and rain were north and east of the center, already over Florida.
Tropical storm warnings were in effect for much of Florida's Gulf coast and could be extended inland as the storm moves slowly east over the state in the next few days.
Debby spawned twisters that killed a woman, badly injured a child and wrecked homes in central Florida in rural Highlands County on Sunday. Florida's Pinellas Country was also hit hard, with flooding in some areas and at least 20 houses with roofs that were partially or fully blown off during a tornado-like storm.
WHITE HOUSE CALL
President Barack Obama called Florida Governor Rick Scott from Air Force One on Tuesday "to ensure the state had no unmet needs" as it responds to the flooding, White House spokesman Jay Carney said.
Obama expressed condolences for the loss of life and damage to homes, and Carney said federal authorities "stood ready to provide additional assistance if necessary."
Scott declared a state of emergency on Monday and ordered all state agencies, including the Florida National Guard, to provide any necessary assistance requested by local governments.
"Because of the broad impact of Tropical Storm Debby, virtually every county in Florida could be affected," Scott said.
Debby was the first tropical storm of 2012 to form in the Gulf of Mexico. The storm idled about a quarter of U.S. offshore oil and natural gas production in the Gulf of Mexico during the weekend, based on figures issued by U.S. offshore regulators.
Big offshore drillers began returning staff to offshore platforms after the storm veered away from the Gulf oil patch on Monday, and production had restarted on Tuesday.
Flash flood warnings were in effect for many areas, including some where streets were already under water, and emergency management officials cautioned that inland flooding was associated with more than half the deaths from tropical cyclones in the United States over the last 30 years.
"Gulf Coast residents and visitors should take Tropical Storm Debby seriously," said Federal Emergency Management Agency director Craig Fugate. "Flooding with Tropical Storm Debby is a very big concern for the Florida Panhandle and portions of the southeast."