(CNN) -- Tropical Storm Fiona kept on track for Bermuda on Thursday evening, but forecasters said some weakening could be expected during the next two days.
A tropical storm warning was issued for Bermuda ahead of Fiona, while a second tropical storm in the Atlantic, Gaston, has been downgraded to a tropical depression.
As of 11 p.m. ET, Fiona, which formed in the wake of Hurricane Earl, was about 390 miles (630 kilometers) south of Bermuda, the National Hurricane Center said. It had top sustained winds of 50 mph (85 kph) and was headed north-northwest at about 16 mph (26 kph).
A tropical storm warning means tropical storm conditions are expected within 36 hours, forecasters said.
The center of Fiona is expected to pass near Bermuda late Friday or early Saturday. Tropical-storm-force winds are expected by late Friday.
Fiona could dump 1 to 3 inches of rain on Bermuda, the hurricane center said. After brushing by the island, Fiona was expected to turn eastward and head out into the open Atlantic, tracking maps showed.
Gaston, which formed on Wednesday, was classified as a tropical depression after its winds dropped below the 39-mph threshold for a tropical storm. However, forecasters said it could re-strengthen, although little change was expected in the next 48 hours.
Gaston was not threatening land Thursday, and no watches or warnings were in effect. As of 5 p.m., the remnant low pressure system was about 1,015 miles (1,465 kilometers) west of the southernmost Cape Verde Islands.
Its maximum sustained winds were about 30 mph (55 kph) and it was heading west-northwest at about 5 mph (7 kph).