NEW ORLEANS (AP) — The Latest on a tropical weather system in the Gulf of Mexico (all times local):

4:50 p.m.

Louisiana Gov. John Bel Edwards has asked the Trump administration for a federal declaration of emergency ahead of Tropical Storm Barry's expected landfall late Friday or early Saturday along the state's coast.

In a letter Thursday to President Donald Trump, Edwards asks that the state receive supplementary federal resources as soon as possible should they be needed. His letter notes that in the past 24 hours, 28 parishes have issued emergency declarations and 14 are in the process of completing such declarations.

Edwards says it is necessary that critical pre-positioning be provided through federal assistance.

Meanwhile, the Louisiana National Guard says Edwards has authorized activating up to 3,000 soldiers and airmen ahead of the storm. Officials say high-water vehicles and boats have been staged and helicopters are ready to support as needed.

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4:10 p.m.

A hurricane warning has been issued for parts of the Louisiana coast ahead of Tropical Storm Barry's arrival.

The U.S. National Hurricane Center issued the warning Thursday afternoon for the Louisiana coast from Intracoastal City to Grand Isle. A tropical storm warning is in effect for other areas including the New Orleans metro area.

Barry is currently a tropical storm with winds of about 40 mph (65 kph), and was offshore about 90 miles (145 km) south of the mouth of the Mississippi River.

Forecasters say the storm is likely to become a Category 1 hurricane before making landfall Friday or early Saturday.

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1:55 p.m.

The Mississippi Emergency Management Agency is telling people in the southern part of the state to be prepared for heavy rain from Tropical Storm Barry as it pushes northward through the Gulf of Mexico.

The agency says people in low-lying areas should have a plan to evacuate before waters rise.

Forecasters say the storm could become a hurricane and make landfall in Louisiana. Effects could be felt in Mississippi by early Friday.

MEMA says there's the potential for storm surge greater than 3 feet (1 meter) on the Mississippi Gulf Coast and the south and central parts of the state could have heavy rainfall and flooding.

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1:30 p.m.

Louisiana Gov. John Bel Edwards says authorities don't expect the Mississippi River to overflow levees as Tropical Storm Barry moves toward the Gulf Coast.

At a Thursday news conference, the governor said high water forecasts for the river have gone down slightly but a change in the storm's direction or intensity could renew the possibility of the levees being topped by a river already swollen by heavy rains and snow melt.

Forecasters say Barry could hit Louisiana as a weak hurricane over the weekend. Edwards said it would be the first time a hurricane made landfall in Louisiana when the Mississippi River was already at flood stage.

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11:55 a.m.

The mayor of New Orleans says the city's water pumps are "working at optimal capacity" as Tropical Storm Barry moves toward the state's Gulf coast.

But speaking at a Thursday news conference, New Orleans Mayor LaToya Cantrell added that flooding is a threat because slow-moving, heavy rains are expected from the storm.

National Weather Service meteorologist says New Orleans could get 10 to 15 inches (25 to 38 centimeters) of rain Friday, Saturday and Sunday. Some isolated areas could see 20 inches (50 centimeters).

Barry could hit Louisiana as a weak hurricane over the weekend.

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10:05 a.m.

Tropical Storm Barry has formed in the Gulf of Mexico and forecasters say it could become a hurricane as it threatens Louisiana's coast.

The U.S. National Hurricane Center says the storm's maximum sustained winds Thursday morning are near 40 mph (64 kph) with additional strengthening expected during the next day or two.

A tropical storm warning is now in effect for the Louisiana coast from the mouth of the Pearl River to Morgan City.

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9:40 a.m.

Plaquemines (PLAK-uh-minz) Parish spokeswoman Jade Duplessis says about 8,000 to 10,000 parish residents are under a mandatory evacuation order as a potential tropical storm brews in the Gulf of Mexico and half of them may need help.

All of the parish's east bank and part of its west bank are under mandatory evacuation orders.

The parish government has set up pickup points on both sides of the Mississippi River. From there, school buses will take people to a registration point and then to evacuation centers.

Duplessis says cats and dogs will be taken in separate vehicles and if owners don't have their own travel crates, the parish will provide them.

The evacuation order took effect at 6 a.m. Thursday. Duplessis says officials hope everyone is out by Friday afternoon.

The disturbance in the Gulf is expected to develop into a tropical storm late Thursday and could hit southern Louisiana as a weak hurricane this weekend.

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9:05 a.m.

The mayor of a barrier island town on Louisiana's coast has ordered a mandatory evacuation as a potential tropical storm brews in the Gulf of Mexico.

Mayor David Camardelle's order takes effect at noon Thursday on Grand Isle, which is accessible only by boat or a single flood-prone state highway.

Other low-lying areas of coastal Louisiana including the towns of Lafitte, Crown Point and Barataria also came under evacuation orders Thursday.

That follows similar orders Wednesday for parts of Plaquemines Parish,. The Mississippi River runs through the parish and could overtop some levees.

The disturbance in the Gulf is expected to develop into a tropical storm late Thursday and could hit southern Louisiana as a weak hurricane this weekend.

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8:10 a.m.

Carnival Cruise Line says it rerouted a cruise ship headed to New Orleans because of the potential tropical storm brewing in the Gulf of Mexico.

The Miami-based company says the more than 3,700-passenger Carnival Valor was sent to Mobile, Alabama, in the interest of safety. A company statement notes that coastal Louisiana is under a hurricane watch and water levels are high on the Mississippi River.

Mobile Mayor Sandy Stimpson tweeted a welcome to Valor passengers and a photo of the ship docked in Mobile on Thursday.

Carnival says arriving passengers will be taken from Mobile to New Orleans on complimentary buses.

The ship was supposed to depart Thursday from New Orleans on its next four-day cruise to Cozumel, Mexico. Instead, passengers will be taken to Mobile by bus from New Orleans.

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12 a.m.

A potential tropical storm brewing in the Gulf of Mexico presents twin troubles for parts of southeast Louisiana.

It could contribute to the rising of an already high Mississippi River, with water reaching the tops of levees this weekend. And there is also the widespread danger of flash floods like the one that walloped New Orleans on Wednesday. Officials said that storm dumped as much as 8 inches (20 centimeters) in parts of the metro area in three hours.

The Gulf disturbance that spawned the floods was forecast to strengthen into a tropical storm by Thursday night.

Forecasters said Louisiana could see up to 12 inches (30 centimeters) of rain by Monday. Some areas could get 18 inches (46 centimeters).

Mississippi and Texas were also at risk of torrential rains.

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