The U.S. Virgin Islands remained on a tropical storm warning Thursday morning, but the hurricane watch was lifted as Tropical Storm Isaac headed westward at 12 mph.

Rain will be the problem, said meteorologist Luis Rosa at the National Weather Service in San Juan around 5:45 a.m. Thursday.

“Showers will become more frequent in the afternoon, and there will be heavy rainfall tonight,” he said.

That holds for all the Virgin Islands, he said. All the islands should see winds in the 20 to 30 mph range with gusts to 40 mph.

“The wind is not going to be a big problem, it’s the heavy rain,” Rosa said.

According to Rosa, Isaac’s center should pass 119 miles south of St. Croix at noon, 157 miles south of St. Thomas at 2 p.m. and 165 miles south of St. John at 1 p.m.

As of the 5 a.m. update, Isaac had winds of 40 mph with higher gusts. Tropical storm force winds reached outward 140 miles from the center.

The storm’s center was at 15.3 degrees north latitude and 64 degrees west longitude, putting it 142 miles south-southeast of St. Croix.

Rosa said the storm was disorganized and took an erratic motion overnight. It reformed during the overnight hours. While it’s still moving west, Rosa said it’s expected to turn to the north northwest.

Overnight, St. John and St. Thomas had several bouts of rain and strong wind. St. Croix reported rain falling at 6:30 a.m.