The Latest on Subtropical Storm Alberto (all times local):

11 p.m.

Tropical storm and storm surge watches have been issued for parts of the U.S. Gulf Coast as Subtropical Storm Alberto slowly moves eastward.

The U.S. National Hurricane Center in Miami said Friday that the tropical storm watch has been issued from Indian Pass, Florida, westward to Grand Isle, Louisiana along a swath that also includes parts of Alabama and Mississippi. The storm surge watch was issued for a stretch from Horseshoe Beach, Florida, to the mouth of the Mississippi River.

Tropical storm watches are also in effect for parts of Mexico and Cuba. Heavy rains are expected in portions of the Yucatan Peninsula and western Cuba.

As of Friday evening, the first named storm of the 2018 hurricane season was centered about 110 miles (177 kilometers) southeast of Cozumel, Mexico.

Its top sustained winds were 40 mph (65 kph). It's expected to continue moving north through the Gulf over the weekend, with gradual strengthening.

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8:45 p.m.

Tropical storm and storm surge watches have been issued for parts of the U.S. Gulf Coast as Subtropical Storm Alberto slowly moves eastward.

The U.S. National Hurricane Center in Miami said Friday that the tropical storm watch has been issued from Indian Pass, Florida, westward to Grand Isle, Louisiana along a swath that also includes parts of Alabama and Mississippi. The storm surge watch was issued for a stretch from Horseshoe Beach, Florida, to the mouth of the Mississippi River.

Tropical storm watches are also in effect for parts of Mexico and Cuba. Heavy rains are expected in portions of the Yucatan Peninsula and western Cuba.

As of Friday evening, the first named storm of the 2018 hurricane season was centered about 100 miles (161 kilometers) southeast of Cozumel, Mexico.

Its top sustained winds were 40 mph (65 kph). It's expected to continue moving north through the Gulf over the weekend, with gradual strengthening.

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5 p.m.

Forecasters have issued tropical storm and storm surge watches for parts of the U.S. Gulf Coast as Subtropical Storm Alberto approaches.

The U.S. National Hurricane Center in Miami said Friday afternoon that the tropical storm watch has been issued from Indian Pass, Florida, westward to Grand Isle, Louisiana along a swath that also includes parts of Alabama and Mississippi. The storm surge watch was issued for a stretch from Horseshoe Beach, Florida, to the mouth of the Mississippi River.

Tropical storm watches are also in effect for parts of Mexico and Cuba.

As of Friday evening, the first named storm of the 2018 hurricane season was centered about 100 miles (161 kilometers) southeast of Cozumel, Mexico.

Its top sustained winds were 40 mph (65 kph). It's expected to continue moving north through the Gulf over the weekend, with gradual strengthening.

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10:30 a.m.

The first named tropical weather system of the 2018 hurricane season has formed. The National Hurricane Center says a disturbance moving toward the Gulf of Mexico is now Subtropical Storm Alberto.

Alberto had top sustained winds of 40 mph (65 kph) early Friday and was located 55 miles (90 kilometers) south of Cozumel, Mexico. The storm was moving north-northeast at 6 mph (9 kph). The storm is expected to bring heavy rain to the Yucatan Peninsula, western Cuba, Florida and the northeastern Gulf Coast throughout the weekend.

A subtropical storm has a less defined and cooler center than a tropical storm, and its strongest winds are found farther from its center. Subtropical storms can develop into tropical storms, which in turn can strengthen into hurricanes.

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8 a.m.

Forecasters say a tropical weather system moving toward the Gulf of Mexico is strengthening.

The National Hurricane Center said Friday that a low pressure system in the northwestern Caribbean Sea has become better defined overnight and could be a tropical depression or storm by Saturday.

They put chances of formation at 90 percent over the next two days.

The system sits east of the Yucatan Peninsula but moving northward. Forecasters say heavy rains are likely across western Cuba, much of Florida and the northern Gulf Coast into early next week.

Portions of the northern Gulf Coast are likely to experience tropical storm force winds and storm surge.

There's also a strong threat of rip currents from Florida to Louisiana.

An Air Force Reserve reconnaissance aircraft is scheduled to investigate.