Tropical storm watches were issued for various Caribbean islands Monday evening for what could soon become the sixth named tropical storm of this year’s Atlantic hurricane season.

Watches for the US Virgin Islands, Puerto Rico, Culebra, and Vieques have been upgraded to a tropical storm warning, according to an 11 p.m. advisory from the National Hurricane Center. A watch is in effect for Martinique and Guadeloupe, Dominica, Saba and St. Eustatius, Dominican Republic on the north coast from Cabo Frances Viejo to the Dominican Republic/Haiti border and Haiti from the northern border with the Dominican Republic to Gonaives.

Forecasters believe the disturbance heading toward the Lesser Antilles could become Tropical Storm Fred later Monday night or early Tuesday morning. It has been more than a month since this year’s fifth named storm – Hurricane Elsa -formed.

The disturbance had maximum sustained winds of 35 mph (55 kmh) with higher gusts and was 40 miles (65 kilometers) east-southeast of Dominica, according to officials. A tropical storm has maximum sustained winds of at least 39 mph (63 kmh). It was moving west-northwest at 15 mph (24 kmh).

The storm is forecast to move through a portion of the southern Leeward Islands Monday night, pass near or over the US Virgin Islands and Puerto Rico late Tuesday and Tuesday night, and near or over Hispaniola on Wednesday.

The storm is expected to produce rainfall totals of 2 to 4 inches (5 to 10 centimeters) over the Leeward Islands, Virgin Islands, and Puerto Rico, with up to 6 inches (15 centimeters) in some areas. The rainfall could lead to flash, urban, and small-stream flooding and potential mudslides across the US Virgin Islands and Puerto Rico.