(CNN) -- A tropical depression formed in the western Caribbean Sea on Sunday, and is likely to become Tropical Storm Rina as it skirts the Honduran coastline, the National Hurricane Center said.
The depression -- the 18th of the 2011 Atlantic hurricane season -- was located off the Nicaragua/Honduras border late Sunday afternoon, forecasters said. The government of Honduras issued a tropical storm watch from Punta Castilla eastward to the Nicaraguan border. A tropical storm watch means tropical storm conditions, including sustained winds of at least 39 mph, are possible within 48 hours.
The depression was moving northwest at near 12 mph, and was expected to turn west-northwest Monday.
"On the forecast track, the center of the depression is expected to pass north of the northeastern coast of Honduras during the next couple of days," the center said.
The depression's maximum sustained winds were at 35 mph, just shy of tropical storm strength, forecasters said.
"Gradual strengthening is expected during the next day or two and the depression is forecast to become a tropical storm tonight or Monday," the center said.
The depression is expected to dump 2 to 4 inches of rain over eastern Honduras, with isolated maximum amounts of 7 inches possible in some spots, according to the center.
The forecast track shows the system brushing Belize as a tropical storm and making landfall near Chetumal, Mexico, on Friday. However, such long-range forecasts are subject to change.