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Flash Flood Watch extended as threat for locally heavy rain continues

Published: Sep. 16, 2021 at 4:40 AM CDT|Updated: Sep. 16, 2021 at 1:10 PM CDT

BATON ROUGE, La. (WAFB) - The National Weather Service has extended the Flash Flood Watch for much of the WAFB viewing area, including metro Baton Rouge, through 7 p.m. on Friday.

FIRST ALERT FORECAST: Thursday, September 16
FIRST ALERT FORECAST: Thursday, September 16(WAFB)

Locally heavy rainfall will remain possible over the next couple of days as what is now post-tropical cyclone Nicholas meanders to our west. That localized threat was all too evident late Wednesday as isolated storms produced 2″-5″ of rain across parts of Baton Rouge, resulting in significant street flooding, especially in the vicinity of LSU.

Today starts out with isolated showers, but rains will become numerous by this afternoon as daytime heating spurs more storm development.

FIRST ALERT FORECAST: Thursday, September 16
FIRST ALERT FORECAST: Thursday, September 16(WAFB)

High temperatures are expected to reach the mid 80s for most before the rains develop.

FIRST ALERT FORECAST: Thursday, September 16
FIRST ALERT FORECAST: Thursday, September 16(WAFB)

Similar to Wednesday, many areas of SE Louisiana and SW Mississippi will receive manageable rains, but pockets of heavier persistent storms could lead to additional flooding. Some of our hi-res guidance indicates that metro Baton Rouge could again be in play for some of those heavy storms.

Little change is expected in our rainy pattern as we head into the weekend. Even as the remnant circulation of Nicholas continues to weaken, it will be replaced by a non-tropical upper-level low. That feature combined with a continued abundance of tropical moisture will result in rain chances running 70% or better through Sunday. Rains should be a bit more focused during the afternoon hours in the days ahead, but any given day could produce some heavy rainfall and localized flooding.

The extended forecast points toward scattered to numerous showers and t-storms continuing through at least the mid part of next week. There is some potential for a cool front to move through during the second half of next week or the following weekend, but confidence in timing and any potential frontal passage is rather low at this time.

FIRST ALERT FORECAST: Thursday, September 16
FIRST ALERT FORECAST: Thursday, September 16(WAFB)

The 7-day outlook from NOAA’s Weather Prediction Center shows an additional 2″ to 4″ of rain falling across the area, with locally higher amounts possible.

FIRST ALERT FORECAST: Thursday, September 16
FIRST ALERT FORECAST: Thursday, September 16(WAFB)

Elsewhere in the tropics, the National Hurricane Center continues to indicate two other areas in the Atlantic are likely to develop in the days ahead. One area of low pressure is located several hundred miles off the southeast U.S. coastline and is given a 70% chance of development as it generally moves northward over the next several days.

Farther out in the Atlantic, low pressure about midway between Africa and the Lesser Antilles is given a 90% chance of development. While this disturbance is likely to develop, it may encounter some rather strong wind shear as it moves farther west.

Finally, NHC is giving another tropical wave about to emerge from Africa a 20% chance of development over the next 5 days.

FIRST ALERT FORECAST: Thursday, September 16
FIRST ALERT FORECAST: Thursday, September 16(WAFB)

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