Tropical Storm Melissa forecast to become a major hurricane. Maps show its path.

Tropical Storm Melissa is expected to bring days of heavy rain to the Dominican Republic, Haiti and Jamaica and may trigger life-threatening flash flooding, the National Hurricane Center says.

It is forecast to become a hurricane by Saturday and a major hurricane by the end of the weekend, the hurricane center said.

Melissa, which is the 13th named storm of the Atlantic season, isn’t expected to have major impacts on the mainland United States.

Tropical Storm Melissa forecast and path

On Thursday night, Melissa’s core was about 150 miles south-southeast of Kingston, Jamaica, and about 270 miles southwest of Port-au-Prince, Haiti, the hurricane center said. Maximum sustained winds were 45 mph, with tropical storm-force winds extending up to 140 miles out from the storm’s center. It was inching north at only 3 mph.

The storm is expected to linger over the central Caribbean for the next several days, according to CBS News meteorologist Nikki Nolan, as it is moving very slowly. It is sitting over very warm waters.

On the forecast track, Melissa “is expected to move closer to Jamaica and the southwestern portion of Haiti during the next couple of days,” the hurricane center said.

Little change in the storm’s strength is expected over the next day or so, but “significant strengthening is expected by late Friday and over the weekend,” the hurricane center said.

A hurricane watch and a tropical storm warning were in place for Jamaica and the southwestern peninsula of Haiti from the border with the Dominican Republic to Port-au-Prince.

Rainfall forecasts

Melissa is forecast to bring anywhere from 8 to 14 inches of rain to portions of the southern Dominican Republic, southern Haiti and eastern Jamaica through Sunday, with locally higher amounts possible, the hurricane center said. “Additional heavy rainfall is possible beyond Sunday,” it continued, but uncertainty about Melissa’s track and speed makes the exact totals harder to predict.

“Regardless, significant, life-threatening flash flooding and numerous landslides are expected,” forecasters said.

Nikki Nolan and

Rob Marciano

contributed to this report.