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Tropical Storm Sally was strengthening as it moved through the Gulf of Mexico, taking aim at southern Louisiana and Mississippi, and National Weather Service projections showed that the system could become a hurricane by Monday afternoon.
Hurricane watches and storm warnings were issued throughout the gulf, including parts of Louisiana, Mississippi, Alabama and the Florida Panhandle, according to the Weather Channel.
The storm is expected to make landfall as a Category 1 storm early Tuesday in Louisiana, bringing 90 mph maximum sustained winds, a storm surge of as much as 11 feet and potentially historic rainfall to the Gulf Coast, according to NBC News meteorologist Bill Kairns.
Between 10 and 20 inches of rain are expected in Louisiana, Mississippi and Alabama, he said.
Louisiana Gov. John Bel Edwards declared a state of emergency Saturday as the storm moved in.
"While we ultimately don't know where Sally will make landfall, much of Southeast Louisiana is in the storm's cone and the risk of tropical storm force or hurricane strength winds continues to increase. Please stay weather aware for the next several days and heed the directions of your local officials. This storm has the potential to be very serious," Edwards said in a statement.
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"Barely two weeks ago, Louisiana suffered a devastating blow when Hurricane Laura came ashore as the strongest hurricane ever to make landfall in Louisiana history, leaving a trail of destruction in its path," Edwards said. "This, when combined with the COVID-19 pandemic, can make us all weary. I implore Louisianans to take their preparations seriously."
A mandatory evacuation order was issued for New Orleans residents outside of levee protection in Venetian Isles, Lake Catherine and Irish Bayou, Mayor LaToya Cantrell said.
By Sunday night, the storm was 160 miles south of Panama City, Florida, and 195 miles east-southeast of the mouth of the Mississippi River, according to the National Hurricane Center. In an 8 p.m. update, the center said the storm was strengthening and slowing down.
The hurricane center said the storm was moving at about 9 mph with winds of 60 mph.
A storm surge warning was in effect from Port Fourchon, Louisiana, to the border of Mississippi and Alabama. Storm surge is also expected at Lake Pontchartrain, Lake Maurepas and Lake Borgne.
A hurricane warning was in effect from Grand Isle, Louisiana, to Ocean Springs, Mississippi, including Lake Pontchartrain, Lake Maurepas and metropolitan New Orleans.
The storm's effects have already been felt in parts of South Florida. The storm dropped nearly 10 inches of rain on Key West, causing flooding and closing streets.