By Collin Eaton and Kathy Finn

NEW ORLEANS, July 13 (Reuters) - Tropical Storm Barry, poised to make landfall as the first Atlantic hurricane of 2019, churned ever closer to Louisiana's shore early on Saturday as most New Orleans residents huddled at home, or in bars, bracing for the threat of severe flooding.

Authorities urged citizens to secure property, stock up provisions and shelter in place. However, some nervous residents opted to flee the city, and tourism officials reported an abrupt exodus of out-of-town visitors on Friday.

Mandatory evacuations were ordered in outlying coastal areas beyond the protection of levees in neighboring Plaquemines and Jefferson parishes south of the city.

The storm, packing maximum sustained winds of 65 miles per hour (100 kph), was on track to reach hurricane strength shortly before crossing the Louisiana coastline southwest of New Orleans on Saturday, the National Weather Service said.

Landfall was expected around sunrise.

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 nearly 60 percent.

U.S. President Donald Trump declared a state of emergency for Louisiana on Friday, freeing up federal disaster assistance if needed.

The impending storm could test beefed-up flood defenses put in place since the 2005 calamity of Hurricane Katrina, which left much of New Orleans underwater and killed about 1,800 people.

TOO MUCH WATER

The brunt of Barry's force was expected to skirt the western edge of New Orleans, avoiding a direct hit on a low-lying city virtually surrounded on all sides by rising waters.

But Mayor LaToya Cantrell said 48 hours of heavy downpours could overwhelm pumps designed to purge streets and storm drains of excess water.

"There is no system in the world that can handle that amount of rainfall in such a short period," Cantrell said on Twitter.

Authorities were paying specially close attention to the levee system built to contain the lower Mississippi River, which winds through the heart of New Orleans and was already above flood stage from months of heavy upstream rainfall over the Midwest.

A coastal storm surge into the mouth of the Mississippi was expected to push its crest to 19 feet (5.79 m) in New Orleans on Saturday, the highest level since 1950 and dangerously close to the top of the city's levees.

New Orleans was already saturated after thunderstorms drenched it with a foot of rain on Wednesday.