Tropical Storm Fiona is on a path to threaten the Virgin Islands and Puerto Rico this weekend.

The Atlantic Hurricane Season’s sixth named storm formed Wednesday evening, and the U.S. National Hurricane Center issued tropical storm watches for the Caribbean’s easternmost islands.

“Interests in the Leeward Islands, the Virgin Islands, and Puerto Rico should monitor the progress of this system,” the center said.

At 8 a.m. EDT on Thursday, Fiona was moving at 13 mph (20 kph) with maximum sustained winds of about 50 mph, forecasters said. Little change in strength is forecast during the next few days.

Fiona was located about 545 miles east of the Leeward Islands, and tropical storm watches were issued for Saba and St. Eustatius, St. Maarten, Antigua, Barbuda, St. Kitts, Nevis, Montserrat, and Anguilla, forecasters said.

Fiona is expected to produce total rainfall of 3 to 6 inches with isolated higher amounts across the northern Leeward Islands, the British and U.S. Virgin Islands, Puerto Rico and eastern Hispaniola. Ocean swells should begin affecting the northern Leeward Islands by early Friday, causing life-threatening surf and rip currents.