FORT LAUDERDALE, Fla. — Tropical Storm Fred began crossing the Dominican Republic on Wednesday afternoon, where the mountainous terrain is expected to weaken the storm to a tropical depression.

But the storm is expected to restrengthen after it clears the Dominican Republic and Haiti, remaining on a course that could take it to Florida by the end of the week.

Tropical storm watches and warnings may be posted for South Florida as early as Thursday morning, said Robert Molleda, warning coordination meteorologist for the National Weather Service in Miami.

The storm’s top wind speed held at 45 mph, according to the 2 p.m. EDT update from the National Hurricane Center. The reach of the storm’s winds extended 60 miles from its center, up from 45 miles earlier in the day.

If the storm affects South Florida, the worst day will probably be Saturday, with the possibilities ranging from blustery, rainy weather to a full-blown tropical storm.

What happens Saturday will depend on whether the storm leans into the northern end of its projected path, which would bring it to South Florida, or the southern end, which would take it through the Gulf of Mexico. And it depends on the strength of the storm itself after it runs the Caribbean’s gantlet of mountainous islands and wind shear.

The major factor for the storm’s future strength is how much it weakens Wednesday as it passes the Dominican Republic and Haiti.

“The biggest question mark is what kind of shape the storm’s going to be in once it crosses the island and comes out on the northwest side,” Molleda said. “Then after that you still have Cuba, which it could pass very close to.”

South Florida has a 10 percent to 15 percent chance of tropical-force winds, which means winds with speeds of at least 39 mph. South Florida could experience heavy rain, with totals of 4 to 6 inches. Another hazard could be tornadoes, since South Florida is likely to be on the northeast side of the storm, the side most likely to produce tornadoes.

The storm’s maximum sustained winds may reach up to 65 mph by Sunday, keeping it under the 74-mph minimum threshold for a hurricane.

The map of possible paths for the storm’s center moved South Florida from the center to the right edge of the cone of concern. The cone now shows a greater chance the storm will head into the Gulf of Mexico.

If the storm reaches South Florida, winds are most likely to arrive late Friday night or early Saturday, but they could reach the area sooner. There’s unusually high uncertainty about both the forecast track and likely strength of the storm, the weather service said.

As of 2 p.m. Wednesday, the storm was moving west-northwest at 16 mph about 30 miles west of Santo Domingo in the Dominican Republic.

Fred is the sixth named storm of the season and the first since Hurricane Elsa moved through the Gulf of Mexico in early July. Fred also marks the first storm of the hurricane season’s busiest period, which runs from mid-August, reaches a peak around Sept. 10 and winds down in October.

Forecasters expect this to be an above-average hurricane season, with NOAA predicting up to 10 hurricanes by the time the season ends Nov. 30.

Fred is forecast to continue moving generally west-northwest from now until Friday before it takes a turn toward the north or northwest.

“How soon that northward turn begins will determine if the system strikes Florida or areas farther west along the Gulf of Mexico coastline,” according to AccuWeather.

Although Fred is forecast to strengthen once it clears the islands of the Caribbean, an upper-level low near Florida in the next couple of days could bring increasing west-southwesterly wind shear, which would limit Fred’s intensification, according to the National Hurricane Center.

Forecasters said projections of the storm’s path are unusually uncertain because it lacked a well-defined center, making its course harder to predict as it heads across the islands of the northern Caribbean Sea.

Fred is expected to move near or over Haiti and the Dominican Republic on Wednesday, move near the Turks and Caicos Islands and the southeastern Bahamas on Thursday, and move north of the northern coast of central Cuba on Friday, the National Hurricane Center said.

Meanwhile, the chances of another storm farther out in the Atlantic have increased. A cluster of thunderstorms off the African coast now has a 50 percent chance of organizing itself into a tropical cyclone, the catch-all term for closed-circulation storms that range in strength from depression to hurricane. The hurricane center on Tuesday had given it a 30 percent chance.

Tropical storm warnings and watches were in effect Wednesday for the Dominican Republic, Haiti, southeast Barbados, Turks and Caicos and surroundings areas.

Forecasters say swells could cause life-threatening surf and rip current conditions across the U.S. Virgin Islands and Puerto Rico through morning and then Haiti and the Dominican Republic later in the day.

Tropical Storm Fred is the first tropical cyclone to form in the Atlantic in more than a month, since the July 1 appearance of the storm system that would become Hurricane Elsa.

The number of storms is likely to increase in frequency over the next few weeks as the season ramps up toward its September peak. The next storm name after Fred is Grace.

Sun Sentinel staff writer Angie DiMichele contributed to this report.