With the storm expected to blow ashore by early Saturday, National Guard troops and rescue crews were stationed around the state with boats and high-water vehicles, helicopters were on standby, and drinking water and blankets were made ready for distribution. Utility repair crews with bucket trucks moved into position in the region. And homeowners sandbagged their property or packed up and left.
Forecasters said Barry could unload 10 to 20 inches of rain across a swath of Louisiana including New Orleans and Baton Rouge, as well as southwestern Mississippi, with pockets in Louisiana getting 25 inches. Some low-lying roads near the coast were already covered with water Friday morning as the tide rose and the storm pushed water in from the Gulf of Mexico.
The National Hurricane Center predicted Barry would come ashore as the first hurricane of the Atlantic season, though a weak one, just barely over the 74 mph windspeed threshold. But center Director Ken Graham said the designation is "not the point here." The real danger, he said, is the rain.
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Barry's downpours are expected to pose a severe test of the improvements made to New Orleans' flood defenses since the city was devastated by Hurricane Katrina in 2005.
The Mississippi River is already running abnormally high because of heavy spring rains and snowmelt upstream, and the ground around New Orleans is soggy because of an 8-inch drenching earlier this week.
Louisiana Gov. John Bel Edwards said on Thursday that authorities do not expect the river to spill over its levees, but he cautioned that a change in the storm's direction or intensity could alter that.
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New Orleans could get its worst drenching in decades, possibly eclipsing the city's wettest day on record - 12.24 inches - on May 8, 1995, forecasters said. The storm could also shatter Baton Rouge's one-day record rainfall of 11.99 inches from April 14, 1967.
President Donald Trump declared a federal emergency for Louisiana, authorizing the Department of Homeland Security and the Federal Emergency Management Agency to coordinate relief efforts.
Late Friday morning, Barry was about 100 miles southwest of the mouth of the Mississippi, and its winds had jumped to 65 mph. Tracking forecasts showed the storm continuing on toward Chicago, swelling the Mississippi River basin with water that must eventually flow south again.
Scientists say global warming is responsible for more intense and more frequent storms and floods, but without extensive study they cannot directly link a single weather event to the changing climate.
About 10,000 people in Plaquemines Parish on Louisiana's low-lying southeastern tip were ordered evacuated on Thursday.
Among the last to leave were 65-year-old Clarence Brocks and his family. The Plaquemines Parish native evacuated many times before and had to rebuild after Katrina wiped out his home. But he said he wouldn't want to live anywhere else.
"I was born and raised here. This is all I know," the Air Force veteran said. "I've been all over the world and guess where I want to be at? Right here."
With lightning flashing in the distance and some streets already covered with water from heavy rains, shoppers at an Albertsons grocery store in Baton Rouge stripped shelves bare of bread. Half the bottled water was gone.
Kaci Douglas and her 15-year-old son, Juan Causey, were among dozens filling sandbags at a fire station in Baton Rouge. She planned to put the bags around the door of her townhouse. "I told my son it's better to be safe than sorry," she said.
Meanwhile, utility crews who may be needed after the storm filled hotel parking lots along Interstate 59 in southern Mississippi.
New Orleans Mayor LaToya Cantrell said Thursday that Barry could dump water faster than the city's drainage pumps can move it. However, the city did not plan to order evacuations because Barry was so close and because it was not expected to grow into a major hurricane.
Hurricane Katrina caused catastrophic flooding in New Orleans 14 years ago and was blamed altogether for more than 1,800 deaths in Louisiana and other states, by some estimates.
In its aftermath, the Army Corps of Engineers began a multibillion-dollar hurricane-protection system that isn't complete. The work included repairs and improvements to some 350 miles of levees and more than 70 pumping stations that remove floodwaters.
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