Severe tropical rainstorm to impact southern Louisiana through the weekend
A tropical rainstorm building along the north-central Gulf Coast is expected to deliver torrential rainfall to southern Louisiana, with a particular threat to the New Orleans metro area, through the rest of this week and into the weekend. Though the storm system remains disorganized, its capacity for dangerous flash flooding is significant.
AccuWeather meteorologists emphasize that this storm, while not yet officially a tropical depression or tropical storm, is still set to unload relentless rain on areas such as New Orleans, where flooding infrastructure is vulnerable due to its below-sea-level elevation. By early Wednesday, the system’s swirling winds were situated near Tallahassee, Florida, while most of the storm energy remained offshore over the warm Gulf waters.
“There’s a narrow window for the system to strengthen into a tropical depression or tropical storm—likely until midday Thursday,” stated Alex DaSilva, Lead Hurricane Expert at AccuWeather, on Wednesday morning.
Even if the system doesn’t officially strengthen, the rainfall threat remains elevated. Weak steering winds are expected to drive the rainstorm westward across southern Louisiana on Thursday, with a stalling pattern possible. This stalling would intensify the rainfall over the same areas for an extended period, greatly increasing the flood risk.
By Friday and continuing through the weekend, the system is projected to expand its reach into the lower and middle Mississippi Valley, bringing localized flash flooding to regions in Mississippi and possibly as far west as Houston, Texas.
A broad swath of southern Louisiana and southern Mississippi is forecast to receive 4 to 8 inches (100 to 200 mm) of rainfall, while isolated zones could see 8 to 12 inches (200 to 300 mm). An AccuWeather Local StormMax™ of 16 inches (about 400 mm) is possible in the heaviest downpour zones.
Rainfall rates of 1 to 3 inches per hour are likely during peak bands of the storm, which will test the urban drainage systems, particularly in cities like New Orleans, which depends on large-capacity pumps to prevent accumulation on roads and in neighborhoods. Low-lying and urban areas throughout Louisiana, southwestern Mississippi, and eastern Texas near the Louisiana border are all at high risk for flooding.
The AccuWeather RealImpact™ Scale assigns this storm a level one, not because of wind strength, but due to the potential for flooding, disruption to travel, economic impact, and risk to life and property.
Though strong wind gusts are not expected to be widespread, any embedded thunderstorms near the Interstate 10 corridor could bring locally damaging wind, and a few tornadoes or waterspouts cannot be ruled out as the storm moves inland on Thursday.
Looking ahead, AccuWeather experts are closely monitoring nearby Gulf waters for additional tropical development later in July.
