Felicia’s winds diminished slightly overnight but the tropical storm maintained a course that would start hitting the eastern Hawaiian islands tonight.

The Big Island, Maui County and Oahu are all under a tropical storm watch. The Central Pacific Hurricane Center said this morning that if expected weakening of Felicia to a tropical depression later today does not occur, some of those islands will be placed on a tropical storm warning by tonight.

“It continues to weaken and we expect that trend to continue,” Raymond Tanabe, a meteorologist with the National Weather Service in Honolulu, said early today. “But the threat is not zero. You could still see some pretty good winds and rainfall.”

“Maui and Oahu will get the highest impact and the most rain,” he said.

Felicia, once a powerful category 4 hurricane, now has 45 mph maximum sustained winds with higher gusts and is moving west at 12 mph. As of 8 a.m. today, it was about 285 miles east of Hilo and about 450 miles east of Honolulu. Tropical storm force winds of 39 mph or more extend up to 125 miles from the center, forecasters said.

“Regardless of the strength of Felicia when it reaches the Hawaiian islands, heavy rains are still expected to occur and flash flooding remains a possibility,” the hurricane center said.

The latest track shows Felicia traveling north of the Big Island as a tropical depression tonight and just south of Oahu later Tuesday.

A swell generated by Felicia has already hit the main Hawaiian islands.

A tropical storm watch means tropical storm conditions are possible in the watch area within 48 hours.

Rainfall and the areas affected are dependent on the track Felicia takes, a weather service report said.

A flash flood watch is in effect for Kahoolawe, Lanai, Maui, Molokai, and the Big Island through Tuesday afternoon, and for Oahu from Tuesday morning through Wednesday afternoon.

“Felicia is expected to produce extremely heavy rainfall with the potential for widespread flash flooding, increasing on Tuesday and continuing into Wednesday,” forecasters said.

People in flood-prone areas need to prepare for the possibility of torrential rains and rock and mudslides. Flooding rainfall could occur well away from the center of Felicia.

A high surf warning is in effect for Oahu, Maui and the Big Island until Tuesday night. The surf will likely exceed the warning level of 15 feet. Kauai and Niihau are under high surf advisory until Wednesday evening.

Public schools remain open today, the Department of Education Web site said. Two Big Island schools, West Hawaii Explorations Academy in Kailua-Kona and Kua O ka La Public Charter School in Pahoa, are closed.

Hawaii Volcanoes National Park, closed most of its roads and campgrounds until “after tropical storm conditions have passed.” Several beach parks on Hawaii’s Big Island were also being closed Sunday afternoon because the storm was expected to increase wave heights. A building swell generated by the storm was expected to hit eastern shores of the eastern Hawaiian islands later Sunday, according to the Hurricane Center.

The Hawaii County Civil Defense advised Big Island residents to be on alert for sudden increases in surf heights and tie down loose items outside their homes. A flash flood watch was issued for the Big Island starting Monday.

Felicia peaked as a category 4 hurricane with winds topping 140 mph on Thursday when it was still in the Eastern Pacific.

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The Associated Press contributed to this report.