(Adds details, changes dateline to MEXICO CITY)
MEXICO CITY, Oct 21 (Reuters) - Hurricane Willa gained strength and churned toward Mexico's Pacific coast, where it was expected to make landfall by Tuesday unleashing torrential rains in its wake, the U.S. National Hurricane Center (NHC) said on Sunday.
The Category 3 hurricane had maximum sustained winds of about 115 miles per hour (185 km), and additional strengthening is expected over the next day, according to the NHC.
The Miami-based forecaster said Willa was expected to become a dangerous Category 4 hurricane on the 5-step Saffir-Simpson scale by Sunday night or Monday.
By Sunday afternoon, the storm was located about 250 miles (402 km) southwest of Cabo Corrientes, on the coast of Jalisco state.
The hurricane center forecast total rainfall of 5 inches to 10 inches (12.5 cm to 25.4 cm) across stretches of Jalisco, Nayarit and Sinaloa states that "would cause life-threatening flash flooding and landslides."
Meanwhile, Tropical Storm Vicente, which formed in the Pacific off southern Mexico on Saturday, began to weaken as it hovered along the coast of southern Mexico on Sunday, located about 230 miles (370 km) southeast of the beach resort of Acapulco, in Guerrero state.
It had maximum sustained winds of 40 mph (64 kph), and the center of the storm would likely "remain just offshore or near the southern coast of Mexico through Tuesday morning," according to the NHC. (Reporting by David Alire Garcia; Editing by Sandra Maler)
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