Updated

Tropical storm Sally is strengthening, prompting hurricane and storm surge warnings for parts of the northern Gulf Coast.

"Sally expected to strengthen tonight and Monday," said the National Hurricane Center, in an advisory issued at 11 a.m. EDT Sunday. "Life-threatening storm surge, hurricane-force winds and heavy rainfall expected along portions of the northern Gulf Coast starting on Monday."

At 11 a.m. EDT Sunday tropical storm Sally was about 135 miles west of St. Petersburg, Florida, and about 280 miles east-southeast of the mouth of the Mississippi River with maximum sustained winds of 60 mph. The storm was traveling west-northwest at 12 mph.

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"The Hurricane Warning along the coast of Louisiana has been extended westward to Morgan City," the National Hurricane Center said, in its advisory. "A Tropical Storm Warning has been issued for the coast of Louisiana from west of Morgan City to Intracoastal City."

"#Sally's slow motion poses a significant risk of flash flooding over southeastern Louisiana, southern Mississippi, southern Alabama, and the Florida Panhandle through Wednesday morning," tweeted the National Hurricane Center on Sunday.

"A Hurricane Warning for #Sally is also in effect for parts of southeastern #Louisiana and southern #Mississippi," the Hurricane Center also tweeted. "Tropical storm force winds are likely to begin there on Monday."

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This Saturday, Sept. 12, 2020 image provided by NOAA shows the formation of Tropical Storm Sally. Tropical Storm Sally has formed off south Florida, becoming the earliest 18th-named tropical storm on record in a busy Atlantic hurricane season. (NOAA via AP)

On Saturday Louisiana Gov. John Bel Edwards also declared a state of emergency in advance of tropical storm Sally.

“Make sure that you do what is necessary to prepare for Tropical Storm #Sally,” he tweeted Sunday.

Officials in the New Orleans area issued a mandatory evacuation order for areas outside of levee protection.

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Other weather systems are also being closely monitored. Hurricane Paulette is moving closer to Bermuda, the National Hurricane Center said early Sunday while tropical depression Rene, which was once a tropical storm, will become a remnant low on Monday.

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Tropical Depression Twenty is expected to gradually strengthen over the next several days.

The Associated Press contributed to this article.

Follow James Rogers on Twitter @jamesjrogers