Tropical Storm Isaias formed in the Gulf on Wednesday and is expected to strengthen into the first Atlantic hurricane of the season.

Forecasters said Isaias will get rapidly more powerful as it moves toward the U.S. Gulf Coast later this week and is expected to become a hurricane by Thursday.

It was not immediately known where the storm might make landfall on the Gulf Coast. The National Hurricane Center's (NHC) initial projections said the center of Isaias could come onshore somewhere between eastern Louisiana and the western Florida Panhandle.

The NHC said there was "an increasing risk of dangerous wind and storm surge impacts along portions of the northern Gulf Coast," adding that floods will be possible due to heavy rainfall.

The Atlantic season has not gone this late without its first hurricane forming since 1905, according to the Associated Press.

An unusually strong El Niรฑo has contributed to the relatively quiet Atlantic hurricane season by increasing wind shear โ€” rapid changes in wind speed or direction with height โ€” which can disrupt tropical storms and make it harder for them to strengthen into hurricanes.

According to the hurricane center's latest advisory, as of 4 a.m. CT on Wednesday:

Isaias was located about 500 miles southwest of the mouth of the Mississippi

It had maximum sustained winds of 40 mph

It was moving east-northeast at 8 mph

There are no coastal watches or warnings in effect, according to the NHC. However, it said hurricane watches would likely be in place in the northern Gulf later Wednesday.

From Friday through the weekend, Isaias is expected to produce rainfall amounts of 3 to 6 inches across the northern U.S. Gulf Coast, extending from far southeastern Louisiana to the Florida Panhandle. Some areas could reach totals of up to 10 inches.

A hurricane watch means that hurricane conditions (sustained winds of 74 mph or higher) are possible within the specified area.