Heavy tropical downpours are expected to keep falling overnight and into Thursday morning as post-tropical cyclone Arthur continues to break apart in Texas, but its outer bands are still steering moisture into Southeast Louisiana. The immediate result is a high flood threat, with torrential rain capable of producing flash flooding and conditions favorable for tornado development.
A Tornado Watch remains in effect until 6 a.m., and a Flood Watch runs through Friday morning. That combination matters now because the rain is expected to arrive hardest while people are asleep and then linger well into the day on the north shore, where heavy downpours could continue into Thursday afternoon.
The heaviest rain is expected in river parishes, the north shore and coastal Mississippi, where the reasonable worst-case total is 10 to 15 inches and isolated locations could go higher. The rest of the south shore is expected to see 3 to 6 inches, with some isolated spots able to exceed that, while lesser accumulations are expected near the mouth of the river. For residents trying to judge what that means on the ground, the range is wide enough to turn one neighborhood into a nuisance-flood zone and another into a serious emergency, depending on how long the rain stalls overhead.
That threat is sharper because the region was not starting from dry ground. Recent heavy rainfall has already saturated the ground, and river levels are already elevated, so even a few more inches can move quickly from ponding to major flooding in vulnerable locations. Residents living along rivers, creeks or in places with a history of flooding should stay alert as precipitation continues into Thursday while the remnants of the system move northeast and leave tropical moisture behind.
What happens next is already clear: the rain does not end with the overnight burst. It keeps going into Thursday in parts of the region, with the north shore holding onto the longest stretch of heavy downpours and the Flood Watch staying in place through Friday morning. That leaves Southeast Louisiana with a familiar problem but a fresh timetable — the biggest rain totals may come before dawn, while the worst flooding can still unfold after the first wave has passed.
