* Gulf system could flood parts of Mexico, Cuba, Florida
* Short-lived Hurricane Chris poses no threat off Canada (Updates with Chris weakening back to tropical storm)
MIAMI, June 21 (Reuters) - A large weather disturbance in the Gulf of Mexico could develop into a tropical cyclone in the next couple of days, forecasters at the U.S. National Hurricane Center said on Thursday.
The mass of thunderstorms had a 50 percent chance of developing into a tropical depression or tropical storm within 48 hours and could bring flooding rain to Mexico's Yucatan Peninsula, western Cuba and southern Florida, the forecasters said.
It stretched from the northwest Caribbean into the Gulf and was expected to move slowly northwest to north in the next two or three days. It was too early to know whether the system would threaten energy interests clustered in the northern Gulf of Mexico.
"It'll probably be out in the central Gulf of Mexico over the weekend. Beyond that it's very difficult to say," said Jack Beven, a senior hurricane forecaster at the hurricane center.
It would become a tropical depression if it wraps around and develops a closed wind circulation. It would become Tropical Storm Debby if those winds reach 39 miles per hour (63 km per hour).
"This one probably will not jump straight to a tropical storm," Beven said. "It's very broad and will take time to consolidate."
Nonetheless, the forecasters said, "Interests along the entire United States Gulf Coast should monitor the progress of this disturbance through the weekend."
Meanwhile, Tropical Storm Chris briefly strengthened into a hurricane in the North Atlantic off Newfoundland on Thursday but posed no threat to land, forecasters said.
Chris became the season's first Atlantic hurricane on Thursday morning when its top winds hit 75 miles per hour (120 km per hour), just over the threshold for hurricane status. By late afternoon it had weakened back to a tropical storm with 70 mph (110 kph) winds.
It was about 585 miles (940 km) east-southeast of Cape Race, Newfoundland, and was expected to weaken further as it made a slow loop over cooler waters during the weekend.
The Atlantic hurricane season runs from June 1 to Nov. 30, but got off to an early start this year. Tropical Storm Alberto quickly fizzled off South Carolina and Tropical Storm Beryl soaked the southeastern United States in May.
The U.S. National Oceanic and Atmospheric Administration predicted there would be nine to 15 tropical storms in the Atlantic basin this year, with four to eight strengthening into hurricanes. (Reporting By Jane Sutton; Editing by Vicki Allen and David Gregorio)