(CNN) — Tropical Storm Fiona was beginning to whip the Virgin Islands and Puerto Rico Saturday and may strike the latter as a hurricane Sunday, posing threats of flooding and mudslides forecasters say could be “life-threatening.”
A hurricane warning is in effect for Puerto Rico, reflecting forecasters’ belief it will strengthen to a hurricane — with sustained winds of at least 74 mph — by the time it’s near or over the island Sunday afternoon.
Hurricane watches, meanwhile, are in effect for the US Virgin Islands as well as parts of the Dominican Republic, the National Hurricane Center said.
Fiona, having pelted Guadeloupe and other northeastern Caribbean islands with heavy rain and winds Friday and early Saturday, was centered over the Caribbean about 75 miles south of St. Croix in the US Virgin Islands as of 8 p.m. ET Saturday, the hurricane center said.
Parts of the Leeward Islands had seen “very heavy rains and flooding,” the hurricane center said Saturday, adding one station in the mountains in southwestern Guadeloupe had recently measured 19.85 inches of rainfall in 24 hours. And a station at Teagues Bay, St. Croix, reported a wind gust of 45 mph, the center said Saturday night.
The storm had maximum sustained winds of 60 mph Saturday night, short of the 74 mph threshold for a Category 1 hurricane, though strengthening is expected as the weekend progresses.
Outer bands already were hitting the Virgin Islands and parts of Puerto Rico since Saturday afternoon, causing some showers and storms. Tropical storm conditions will continue across parts of the Leeward Islands and were beginning to reach the US and British Virgin Islands, from where they will spread westward, across Puerto Rico Saturday evening and into the night and then to parts of the Dominican Republic late Sunday, the hurricane center said.
More than 19,000 homes and businesses were without power in Puerto Rico around 8:30 p.m. ET, according to PowerOutage.us.
The storm is expected to begin trekking in a northwestward motion Sunday through Tuesday, the hurricane center said.
“On the forecast track, the center of Fiona will move south of the U.S. Virgin Islands this evening, approach Puerto Rico tonight, and move across Puerto Rico by Sunday afternoon,” it said. “Fiona will then (move) offshore of the Dominican Republic on Monday and near or to the east of the Turks and Caicos Islands on Tuesday.”
Fiona is expected to become a hurricane before it reaches Puerto Rico’s southern coast on Sunday, the hurricane center added. And it will likely get stronger as it moves over the southwestern Atlantic Monday and Tuesday, the center added.
One of Fiona’s biggest threats is the rain it’s expected to dump, especially on Puerto Rico: generally 12-16 inches, with 20 inches in isolated areas there.
“These rains are likely to produce life-threatening flash flooding and urban flooding, along with mudslides in areas of higher terrain, particularly in portions of Puerto Rico and the eastern Dominican Republic,” the hurricane center said.
Hurricane conditions were expected on Puerto Rico on Sunday — and are possible on the US Virgin Islands on Saturday night, the hurricane center said.
Fiona became a tropical storm over the Atlantic on Wednesday before entering the eastern Caribbean on Friday.
Expectations of heavy rain
Here is how much rain is expected in certain locations over the next few days, according to the hurricane center:
• Leeward Islands, including Guadeloupe, and the northern Windward Islands: 2-4 inches on top of what they’ve already received.
• British and US Virgin Islands and Puerto Rico: 4-6 inches, with isolated areas of 10 inches possible.
• Puerto Rico: 12-16 inches, with isolated areas of 20 inches possible.
• Dominican Republic: 4-8 inches, with isolated areas of 12 inches possible, particularly on the far eastern coast.
• Haiti: 1-3 inches, with isolated maximum totals of 4 inches.
• Turks and Caicos: 4-6 inches.
A flood watch is in effect through Monday afternoon for the US Virgin Islands and parts of Puerto Rico, the National Weather Service said.
Storm surges — ocean water pushed onto land — of 1 to 3 feet also are possible for Puerto Rico’s southern coast. Surges of 1 to 2 feet are possible for the US Virgin Islands, the hurricane center said.
This is the first time in more than three years Puerto Rico has been issued a hurricane watch or warning. The last time was in August 2019, when Hurricane Dorian passed the island as a Category 1 storm.
A few tropical storms have passed the island since then, but Dorian was the last storm at hurricane strength to pass within 50 miles, CNN meteorologists said.
Hurricane Maria devastated Puerto Rico nearly five years ago — making landfall as a Category 4 storm on September 20, 2017, killing several thousand people and tearing apart an antiquated power grid, leaving more than one million people without electricity or running water for months.
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