MIAMI (CBS News) — A storm system moving quickly toward the central U.S. Gulf Coast strengthened to a tropical storm early Monday, according to the National Hurricane Center.

CBS News reports at 11 a.m. ET Tropical Storm Gordon was located about 60 miles west-northwest of Key Largo, Florida, moving west-northwest at 16 mph. Maximum sustained winds were clocked at 45 mph.

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A hurricane watch was issued for the Gulf Coast from the mouth of the Pearl River to the Alabama-Florida border. Tropical storm warnings stretched from portions of South Florida (from Golden Beach to Bonita Beach), and for the Florida Keys (from Craig Key to Ocean Reef), including Florida Bay, and from the Okaloosa-Walton County Line westward to east of Morgan City, Louisiana, including Lake Pontchartrain and Lake Maurepas.

The National Weather Service said that Naples, Marco Island, and Everglades City in Florida were among the locations that could expect hazardous weather over the next 36 hours.

In addition to flash flooding, the weather service says tornadoes are possible through Monday night across the southern and west-central Florida peninsula.

Meteorologist Danielle Niles of CBS’ Boston station WBZ says the threat along the Gulf Coast means heavy rain as well as storm surge.

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Storm surges from 3 to 5 feet are expected from Shell Beach to the Mississippi-Alabama border, and from 2 to 4 feet from Navarre, Fla., to the Mississippi-Alabama border, and from Shell Beach to the mouth of Mississippi River. Southern Louisiana to the Texas border could see surges of 1 to 2 feet.

The National Weather Service says Gordon is expected to pass over the Florida Keys and the southern portion of the Florida peninsula Monday morning, reaching the central Gulf Coast by late Tuesday or Tuesday evening.

The system could dump 2 to 4 inches of rain over parts of the Bahamas, the Florida Keys and South Florida through early Tuesday, with some areas of Florida getting up to 8 inches, according to officials at the National Hurricane Center. Gordon is expected to produce rain accumulations of 4 to 6 inches over southern Alabama, southern Mississippi and Louisiana, with some isolated areas receiving up to 8 inches, through early Thursday. Rainfall is expected to stretch into Missouri and Iowa.

The storm threat comes amid major flooding in the Midwest, due to a slow-moving storm that has brought flash flood watches and warnings from Kansas to Nebraska, stretching to portions of Iowa and northern Illinois.

Meanwhile, Tropical Storm Florence continues to hold steady over the eastern Atlantic on Monday morning, about 895 miles west-northwest of the southernmost Cabo Verde Islands.

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Florence was moving toward the west-northwest near 16 mph and maximum sustained winds of 60 mph. Forecasters say little change in strength is expected in coming days and no coastal watches or warnings are in effect.