People abandon a car on an impassable street flooded by rains caused by Tropical Storm Melissa in Santo Domingo, Dominican Republic, on Oct. 24.Ricardo Hernandez / AP

Tropical Storm Melissa is expected to intensify into a hurricane in the Caribbean on Saturday, bringing with it catastrophic flash flooding and potential landslides.

The slow-moving storm is already responsible for the deaths of at least three people in Haiti. Meteorologists warn the storm could become a Category 4 hurricane, bringing major rainfall and destructive winds to the island of Jamaica.

A hurricane warning is in effect for Jamaica, and a hurricane watch is in place for the southwestern peninsula of Haiti, from the border with the Dominican Republic to Port-au-Prince. Watches could be in effect for portions of eastern Cuba later today, and total rainfall of 4 to 8 inches, with amounts up to 12 inches, is possible into Tuesday.

In an 8 a.m. ET update on Saturday, the National Hurricane Center said the slow-moving storm is crawling west-northwest at 1 mph. At the time of the update, the storm was about 160 miles southeast of Kingston, Jamaica's capital, and 235 miles southwest of Port-au-Prince, the Haitian capital.

The NHC warned of "life-threatening and catastrophic flash flooding and landslides" through the weekend in Jamaica and southern Hispaniola, the island that comprises Haiti and the Dominican Republic.

The Haitian Civil Protection Agency said that two people died Thursday in a landslide in Fontamara, a suburb of Port-au-Prince. Earlier, the agency said a man in his 70s was killed by a falling tree in the southern coastal town of Marigot, while five people were injured in the Artibonite region.

Already, dozens of water supply systems are offline in the Dominican Republic, affecting more than 500,000 customers, with downed trees and traffic lights causing disruption.

Tropical Storm Melissa, forecast to become major hurricane, barrels toward Jamaica and Cuba