SAN JUAN, Puerto Rico -- Beryl weakened to a tropical storm Saturday but is still expected to dump heavy rain over the Lesser Antilles at the end of the weekend on its way to the eastern Caribbean, bringing a new threat to islands still rebuilding from last year's storms. A tropical storm warning was issued for Dominica, which was battered by Hurricane Maria in September as a Category 5 storm, and Guadeloupe

The island's meteorological service said weather conditions would start deteriorating Saturday night and warned of six to 12 inches of rain, with the storm expected to cross over or near Dominica late Sunday or early Monday.

Beryl was named the first hurricane of the Atlantic season Friday. The National Weather Service said late Saturday that the storm was moving at west-northwest at 18 mph, and was expected to hit the eastern boundary of the Caribbean Sunday. Maximum sustained winds have decreased to 45 mph, and additional weakening is predicted over the next 48 hours.

This graphic from the National Hurricane Center shows the projected path of Tropical Storm Beryl on Saturday, July 7, 2018. National Hurricane Center

Dominica Prime Minister Roosevelt Skerrit said in a public address that the storm's track and intensity could still change and urged people to remain alert. "They should not let their guard down," he said.

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He also asked people to store water because he said the government would be shutting down the water system as a preventive measure.

A tropical storm watch was issued for the French Caribbean territories of Martinique, Guadeloupe, St. Martin and St. Barts as well as the islands of Barbados, St. Lucia, Saba and St. Eustatius. Deeper into the Caribbean, a state of emergency was declared in Puerto Rico, where Maria caused more than an estimated $100 billion in damage.

The Federal Emergency Management Agency (FEMA) tweeted Friday that it was coordinating with the governments of Puerto Rican and the U.S. Virgin Islands as the storm approached.

We're coordinating closely with the governments of PR & the U.S. Virgin Islands to keep an eye on #Beryl & prepare for any potential impacts. History shows that storm tracks can change quickly & unexpectedly so please monitor the forecast & listen to directions from officials. https://t.co/8dZXVCZ2jr — FEMA (@fema) July 6, 2018

People in the Caribbean were taking no chances. Long lines were reported outside grocery stores on the islands of Dominica, Puerto Rico and elsewhere as people bought food and water. Among those stocking up was Sandra Whitcher, an owner of Coffeeriver Cottages in Dominica.

"Here's hoping it misses us," she said, adding that crews fortified the roofs on all seven cottages that survived Hurricane Maria. "I can't say I'm not scared, but I know we have prepared as much as we can possibly do."

Forecasters said Beryl is expected to weaken further after entering the Caribbean. It was expected to pass about 70 miles south of Puerto Rico on Monday, but forecasters warned the storm-wracked U.S. territory could see up to 30 mph winds and heavy rains that could cause flooding and mudslides.

Meteorologist Odalys Martinez said in a phone interview that conditions in Puerto Rico would deteriorate late Sunday, with up to 3 inches of rain possible.

"There is a lot of uncertainty," she said.

Forecasters said Beryl probably would dissipate once it moved south of Haiti and the Dominican Republic on Tuesday or Wednesday.

Puerto Rico Gov. Ricardo Rossello declared a state of emergency for the island and suspended work on Monday.

Rossello told reporters the island would probably experience power outages, given that its electricity grid has become more vulnerable since Hurricane Maria. He said, however, that the recovery should be quicker since there are more power restoration crews and equipment on the island now.

The governor urged people without sturdy roofs to move to one of the 424 shelters that the government planned to open across the island. He recently noted that some 60,000 people still have only tarps for roofs.

"There are a lot of Puerto Ricans who are in a vulnerable position," Rossello said. "We are keeping an eye on this minute by minute. It is not the moment to panic, but it's the moment to prepare."

Puerto Rico Health Secretary Rafael Rodriguez urged all those with serious health conditions, including diabetics, to seek shelter at health facilities, which have generators.

Meanwhile, a tropical depression formed in the Atlantic well off the North Carolina coast, but forecasters said there were no coastal watches or warnings in effect. The hurricane center said it would likely become a tropical storm Saturday night or Sunday and continue strengthening over the next few days.

At 11 a.m. EDT, the storm was centered about 150 miles south-southeast of Cape Hatteras with maximum sustained winds of 30 mph. It was moving north-northwest at 2 mph.