Tropical downpours raise flood threat overnight in New Orleans Weather

New Orleans weather is set for tropical downpours overnight into Thursday morning as post-tropical cyclone Arthur dissipates in Texas. A Tornado Watch remains in effect until 6 a.m., and a Flood Watch runs through Friday morning.

The heaviest rain is expected in river parishes, the north shore, and coastal Mississippi, where 10 to 15 inches of rain is possible with isolated higher amounts. The remainder of the south shore is expected to get 3 to 6 inches, with lesser accumulations near the mouth of the river.

Arthur moisture over Southeast Louisiana

Upper-level winds are channeling outer bands of tropical moisture into Southeast Louisiana, keeping torrential downpours in place overnight. The forecast calls for flash flooding and conditions favorable for tornado development while the system weakens farther west.

Rainfall will continue until early Thursday morning in the far southern areas once heavy precipitation starts, while residents on the north shore should expect persistent downpours well into Thursday afternoon. As the remnants move northeast, tropical moisture will keep the rain threat going into Thursday, especially north of the lake.

Flood risk on the north shore

The flooding concern is higher because recent heavy rainfall has already saturated the ground and river levels are elevated. Residents along rivers, creeks, and in areas with a history of flooding should stay vigilant as the forecast rain may trigger major flooding in vulnerable locations.

That leaves the north shore facing the longest stretch of heavy rain and the greatest exposure to the 10 to 15 inch worst-case range. Farther south, the risk is still serious but the totals are expected to be lower unless isolated pockets pick up more than forecast.

Rain totals through Friday

The immediate watch window runs through 6 a.m. for tornadoes and through Friday morning for flooding. For residents in Southeast Louisiana, the practical next step is to treat low-lying roads, river corridors, and flood-prone neighborhoods as the first places most likely to see trouble before the rain ends.