Fernanda was downgraded to a tropical storm overnight and is expected to continue weakening as it enters the Central Pacific, but forecasters are still warning of its potential impact on Hawaii’s surf and weather.

At 5 a.m. today, Tropical Storm Fernanda was about 1,045 miles east of Hilo and packing maximum sustained winds of 65 mph, according to the National Hurricane Center in Miami. Fernanda is moving west-northwest at 12 mph. Tropical-storm-force winds extend outward up to 90 miles from the center.

The storm peaked as a Category 4 hurricane in the Eastern Pacific last weekend, but has been fading as it moves over cooler waters and faces wind shear.

“Additional weakening is forecast during the next 48 hours, and Fernanda could become a tropical depression on Friday,” weather officials said.

The National Hurricane Center’s forecast shows Fernanda weakening to a post-tropical cyclone by Saturday and degenerating into a remnant low by Sunday — well before the system reaches Hawaii, perhaps by Monday. However, the end of the latest five-day forecast map has most of the state, excluding Hawaii island, in the storm system’s so-called “cone of uncertainty.”

An east swell generated by Fernanda is building and a high surf advisory is in effect for eastern shores of the Big Island and Maui, with waves from 5 to 8 feet expected at least through 6 a.m. Friday. Forecasters with the National Weather Service in Honolulu said to expect choppy surf and strong rip currents that will make swimming dangerous.

The east swell is combined with expected arrival of the summer’s last bout of “king tides,” which are a combination of higher-that-usual tides and sea-level rise.

The weather service issued a king tides advisory for the next several days, saying the greatest potential for coastal flooding will be during the mid- to late-afternoon hours through this weekend.

The simultaneous Fernanda-inspired east swell and the king tides, “may cause greater wave run-up along exposed windward coastlines, especially during high tide,” forecaster said this morning in a special weather statement. “Impacts of the king tides may include flooding of beaches that are normally dry, salt water inundation of typically vulnerable low-lying roads, docks, boat ramps and other coastal infrastructure.”

Depending on the exact track of Fernanda, much of the state could see increased rain and thunderstorms by early next week. But maximum sustained winds are expected to be about 25 mph by that time.

The National Hurricane Center, which monitors the Eastern Pacific, is also tracking two other storms systems.

Tropical Storm Greg, with maximum sustained winds of 50 mph, was becoming better organized and is now expected to be a Category 1 hurricane by this weekend. It is forecast to weaken back to a tropical storm by early next week when it will be approaching the Central Pacific. At 5 a.m. Hawaii time today, Greg was 705 miles south-southwest of the southern tip of Baja California, moving west at 10 mph.

Tropical Depression Eight-E, meanwhile, was about 1,085 miles from Baja with 30 mph winds, but is expected to fade into a post-tropical low by Friday, forecasters said.