At 8 a.m., Matthew was about 400 miles southeast of Jamaica's capital, Kingston, and 365 miles south of Port-au-Prince, Haiti, and moving westward near 7 mph.
The storm is expected to turn toward the west-northwest later today, followed by a turn toward the north-northwest on Sunday and north on Monday. Matthew is expected to produce total rain accumulations of 15 to 25 inches over southern Haiti... with possible isolated maximum amounts to 40 inches.
The storm is a powerful Category 4 (Saffir-Simpson scale) with maximum sustained winds now at 150 miles per hour with higher gusts.
The National Hurricane Center said Matthew would likely still be a powerful hurricane on Monday when it is forecast to pass very close to or over Jamaica. Forecasters will know a lot more about the future track of Matthew after the hurricane completes a northward turn by late Saturday or early Sunday, the report says.
A hurricane warning means that hurricane conditions are expected somewhere within the warning area.
United States hurricane forecasters predicted rainfall totals between 10 and 15 inches in Jamaica, with some areas getting as much as 25 inches.
Important to note that on that path it would also impact Haiti and the Dominican Republic.
Hurricane Matthew became the fifth hurricane of the 2016 Atlantic hurricane season on Thursday, but it's still unclear if it will eventually pose a threat to the U.S.
The hurricane watch issued for Jamaica indicates that hurricane conditions are possible by Monday.
UPDATE 8 a.m.: Hurricane Matthew remains a Category 4 with maximum sustained winds around 155 miles per hour Saturday morning. A watch is typically issued 48 hours before the anticipated first occurrence of tropical-storm-force winds, conditions that make outside preparations hard or risky.
"This still looks like a high-impact event for Jamaica and Haiti", Peck said.
Hurricane-force winds extended outward up to 45 miles (75 kilometers) from the center and tropical-storm-force winds extend outward up to 205 miles (335 kilometers). Located approximately 360 miles southeast of Jamaica, the storm was almost stationary for about 6 hours this evening but has begun to move northward in the past couple of hours.
Emergency management authorities banned boating starting Saturday, particularly along the impoverished country's southern coastline, but numerous fishing skiffs could still be seen off the south coast.
The hurricane center was also monitoring another tropical wave to the east of Matthew on Saturday morning.