Meteorologists warned that torrential rain - as much as 2 feet (60 cm) in some places - could unleash severe flooding as the storm moves inland from the Gulf of Mexico, where oil and gas operations have already cut production by almost 60 percent. Powerful winds and whipping rain have already lashed the Gulf Coast, with National Oceanic and Atmospheric Administration (NOAA) forecasting up to 25 inches (60cm) of rain accumulation in parts.
For many, the storm and potential for large-scale flooding revived unpleasant memories of deadly Hurricane Katrina.
Lifelong New Orleans resident Terrence Watkins grabbed supplies at a Costco, saying he has a few simple rules for big storms.
Almost all businesses in Morgan City, about 85 miles (137 kilometers) west of New Orleans, were shuttered with the exception of Meche's Donuts Shop.
The National Hurricane Center said Saturday afternoon that the storm's maximum sustained winds have fallen to 65 miles per hour.
"The big thing will be the rain with this system", said Paul Walker, a meteorologist with AccuWeather Inc.in State College, Pennsylvania. "They could get four times as much as they get for the entire month".
But the extent of the damage - and whether it will be at least partially offset by benefits such as disruption of the notorious Gulf of Mexico "dead zone" - is hard to predict, they say.
Winds could also be gusty in southwest Alabama today.
After it comes ashore, it will quickly break up as it rains itself out.More news: Digital Tax Passed In France Is Aimed At U.S. Tech Giants
Less than 1 inch is expected east of Interstate 65. Barry probably won't be remembered for its winds.
"There are going to be short-term effects on the ecosystem", Muth said.
Officials predicted the hurricane would make landfall near Morgan City, west of New Orleans.
Companies have cut 59 per cent of oil and 49 per cent of natural gas output in the Gulf. The storm is producing sustained winds at 70 miles per hour but is moving northwest slowly at 5 miles per hour.
While New Orleans authorities refrained from ordering evacuations and advised residents to shelter in place instead, tourism officials reported an exodus of hotel guests checking out early on Friday.
The river was expected to surge again to about 17 feet on Monday, the weather service said.
He was keeping a close eye on the nearby Mississippi River.
Louisiana is already under pressure from floods after the months of rain that have set records across the USA and prevented farm fields from being planted.
Officials from the U.S. Army Corps of Engineers, which maintains the levees, have insisted that no significant breaching of the six-metre-high levees in New Orleans was likely.More news: Lil Nas X -"Old Town Road" feat. Young Thug & Mason Ramsey (Remix)
Others hunkered down to ride out the squall, despite mandatory evacuation orders and the risk of unsafe storm surges.
Mike Yenni, president of Jefferson Parish near New Orleans, said the community had taken the "unprecedented" step of closing hundreds of flood gates, largely due to the high levels of the Mississippi.
The spillway, built in 1938 to provide a safety valve during flooding, has been open for a record number of days this year, said David Muth of the National Wildlife Federation's Gulf Restoration Program.
USA benchmark West Texas Intermediate crude traded above $60 a barrel on Friday, while natural gas futures are headed for a third straight weekly gain.
The storm is putting 70 per cent of newly minted U.S. LNG capacity at risk, with Cheniere Energy Inc.'s Sabine Pass export terminal and Sempra Energy's Cameron facility potentially in its path.
The storm may have the biggest impact on oil products, with the Louisiana coast home to almost 40 per cent of U.S. Gulf Coast refining capacity.
Here, the gate of the US Customs House in New Orleans is seen sandbagged in the hope of stemming the surge.
Robinson, of Augusta, Georgia, said she doesn't know what will happen to plans for her uncle's memorial if Barry swamps the city.More news: Tour de France rider’s $12k bike SPLITS IN HALF during crash