Tropical Storm Melissa dumped heavy rain on Hispaniola as forecasters warned Wednesday of a significant flood risk in parts of the Caribbean region in the coming days.

The rains snarled traffic in the Dominican Republic’s capital, Santo Domingo, and games in the country’s professional baseball league were canceled.

People in Haiti grew concerned over the possibility of heavy flooding, which has devastated the country during past storms given widespread erosion.

Melissa had maximum sustained winds of 50 mph (80 kph) early Wednesday and was centered about 325 miles (520 kilometers) south-southwest of Port-au-Prince, Haiti, the U.S. National Hurricane Center in Miami said. It was moving west at 12 mph (19 kph).

A hurricane watch was in effect for southern Haiti, while Jamaica was under a tropical storm watch.

Five to 10 inches (12-25 centimeters) of rain was possible in southern Haiti and the southern Dominican Republic through Friday, with greater amounts in some areas.

Several inches also were expected in Jamaica, with smaller amounts forecast for northern areas of Hispaniola, Aruba and Puerto Rico.

More heavy rain was possible past Friday, and there was a significant risk of flash flooding and landslides for the affected areas.

Melissa was forecast to gain strength gradually, but the U.S. forecasters warned that its track and forward movement were uncertain and people in the region should remain alert.