• Tropical storm warnings have been issued for several Caribbean islands.
  • Fiona became the Atlantic hurricane season’s sixth named storm after forming Wednesday evening.
  • Rainfall of 4 to 6 inches is likely in the U.S. Virgin Islands and Puerto Rico by the weekend.
  • Forecasters say it’s still unclear whether the storm will impact the U.S.

Tropical Storm Fiona continued to churn across the Atlantic Ocean Thursday and forecasts show it taking aim at Puerto Rico and the Virgin Islands, threatening heavy rain, wind and rough surf this weekend, the National Hurricane Center said.

Tropical storm warnings have been issued for several Caribbean islands, including Antigua, Barbuda, St. Kitts, Nevis, Montserrat, Anguilla and St. Maarten. According to Weather.com, tropical storm conditions are expected in the warning area within 36 hours, or in this case by Friday night.

Tropical storm watches were issued Thursday afternoon for Puerto Rico and the U.S. Virgin Islands, which means that tropical storm conditions are possible within the watch area, generally within 48 hours, the Hurricane Center said. 

As of 11 p.m. Thursday, the center of Fiona was located about 335 miles east of the Leeward Islands and heading west at a speed of 15 mph. Fiona had maximum sustained winds of 60 mph. Tropical-storm-force winds extend outward up to 140 miles, mainly to the north of the center of the storm, the hurricane center said.

It became the Atlantic hurricane season’s sixth named storm Wednesday evening.

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Fiona brings heavy rain, flood threat

Rainfall of 4 to 6 inches is likely in the U.S. Virgin Islands and Puerto Rico by the weekend, with isolated maximum totals of 10 inches across eastern Puerto Rico. “These rains may produce flash and urban flooding, along with isolated mudslides in areas of higher terrain,” according to the hurricane center.

Although Fiona’s winds are forecast to strengthen over the coming days to 70 mph, current predictions keep it just below hurricane strength of 74 mph. Wind shear in the Gulf of Mexico and southwest Atlantic could limit strengthening of the system.

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Ocean swells should begin affecting the northern Leeward Islands by early Friday, causing life-threatening surf and rip currents, the hurricane center said.

Will Fiona impact the US?

The eventual track and strength of Fiona remain uncertain, forecasters said. Some computer models show the storm curving out to sea while others show it coming closer to the U.S. East Coast, potentially as a hurricane.