textproduct: New Orleans/Baton Rouge

KEY MESSAGES

Updated at 1125 PM CDT Tue Sep 29 2026

- Scattered to locally numerous showers and a few storms will return to the area Thursday evening. One or two storms could become strong, producing gusty winds, frequent lightning and brief periods of heavy rainfall.

- Confidence is increasing that widespread rain and embedded thunderstorms will affect the area Friday through at least Sunday. While specific rainfall totals are still uncertain, heavy rain and at least localized flash flooding will be a threat. Residents should continue to monitor the forecast for updates regarding this threat.

SHORT TERM

(Now through Thursday night) Issued at 1125 PM CDT Tue Sep 29 2026

Very nice day once again setting up for today, but this will start to change slowly late Wed into Thu. Moistening of the low layers occurs first with the possibility of a few showers developing late today as well as again late in the day Thu. Most of Thu looks good but deep moisture will begin to move in from the gulf possibly overnight Thu into Fri and this is where most of our rainfall with this system will come from. More on that in the extended.

LONG TERM

(Friday through Tuesday) Issued at 1125 PM CDT Tue Sep 29 2026

Friday through Monday will be the primary focus for active weather messaging. A tropical wave will be move northwestward out of the Caribbean and toward the northern Gulf coast, bringing deep tropical moisture to the area. At the same time, an upper trough will lift into the Mid Mississippi River valley, eroding the western periphery of the upper ridge centered off the SE CONUS. This will force a slow- moving cold front toward the area as well. These two systems will interact resulting in widespread rainfall with embedded thunderstorms across the local area mainly from Friday through Sunday, with the most intense rain tapering off by Monday.

Most guidance indicates precipitable water (PWAT) values will be between 2.3 to 2.6 inches across much of the area by late Friday with similar values Saturday and Sunday. PWAT values like these are near the daily record maximum observed values for the Oct 2-4 time frame. This will result in prime conditions for efficient rainfall processes, and in fact the model forecast sounding profiles are basically moist adiabatic from the surface to the tropopause. Deep tropical moisture of this nature is synonymous with excessive rainfall events.

Heaviest rain will likely occur late Friday into Sunday when instantaneous rates of over 4 inches per hour will be possible in the heaviest storms. Rainfall rates like these, even over short periods can easily overwhelm drainage capacity in urban and other poor drainage areas. If forecast confidence continues to increase regarding the excessive rainfall risk, additional upgrades and expansion of risk areas will be possible with the new excessive rainfall outlooks in the coming days.

Current storm totals for the Friday through Sunday period are forecast in the 3-6" range, but this comes with a big caveat that there will likely be pockets of higher totals. The upper end potential is tough to nail down at this point given the several days lead time, but it certainly wouldn't be out of the question for a couple places to see well over 6" the three-day period.

If there's any good news to gleam, it's that rivers across the region are at base flow or lower right now and thus storage capacity is high. Current ensemble guidance is generally indicating a 10% or lower chance of reaching minor flood stage at any given river forecast point. Wouldn't be surprised to see those probabilities come up in a few places as the forecast itself becomes clearer and the range of possibilities therefore decreases. But for now, this appears to be more of a flash flood concern than a significant river flood concern.

Beyond Monday, the next thing that will need to be watched will be the progression of the stalled front offshore. While some global guidance indicates that the boundary will move the tropical moisture with it offshore. However, it's possible that the front never clears out fully and additional days of elevated PoPs and PWATs linger even into next week.

AVIATION

(06Z TAFS) Issued at 1125 PM CDT Tue Sep 29 2026

VFR through this cycle.

MARINE

Issued at 1125 PM CDT Tue Sep 29 2026

As the week progresses, winds will begin to strengthening to 15 to 20 knots by Thursday or Thursday night. Showers and some thunderstorms will begin to increase in coverage toward the end of the week as well as a tropical wave moves through the northern gulf and interacts with an approaching weak cold front.

LIX WATCHES/WARNINGS/ADVISORIES

LA...None. GM...None. MS...None. GM...None.