textproduct: New Orleans/Baton Rouge

KEY MESSAGES

Updated at 1250 PM CDT Tue Sep 29 2026

- Scattered to locally numerous showers and a few storms will return to the area Thursday afternoon. 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) Issued at 1250 PM CDT Tue Sep 29 2026

Weather will remain fairly quiet through tomorrow as mid/upper ridging continues to suppress convection.

Expect to see a rather quick increase in atmospheric moisture beginning Thursday as deeper tropical moisture begins to move into the area. At the same time, the mid/upper ridging will begin to break down as an upper trough moves through the plains states toward the Mississippi Valley.

This will allow for scattered to locally numerous showers to develop mainly during the afternoon hours as daytime heating will be necessary to break through the remaining cap. That being said, we can't rule out a couple thunderstorms, and any storms that do break through the cap will be capable of producing gusty winds, lightning and and brief periods of heavy rainfall.

Temperatures will remain warmer than normal through the period.

LONG TERM

(Friday through Monday) Issued at 1250 PM CDT Tue Sep 29 2026

Friday through Monday look to be quite active weather-wise. Generally speaking, a tropical wave will be moving northwestward out of the Caribbean and toward the northern Gulf coast. At the same time, the previously mentioned upper trough will move into the middle mississippi valley before flattening and lifting northeastward. 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 late Friday through Sunday, with the most intense rain tapering off by Monday.

To put the forecast moisture availability in perspective, most guidance indicates precipitable water values will be approaching 2.5 inches across much of the area by late Friday with similar values Saturday and Sunday. PW values like these are well above the 90th percentile for this time of year and nearing the daily 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.

Heaviest rain will likely occur Saturday 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. Currently we are highlighting a slight risk of excessive rainfall/flash flooding for Saturday, but if confidence continues to increase in this threat, would not be overly surprised to see that threat level increase to moderate. Expect to see a slight risk introduced for Sunday when Sunday becomes "day 5" tomorrow as well.

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 really 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 be approaching the 10" mark over 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.

AVIATION

(18Z TAFS) Issued at 1250 PM CDT Tue Sep 29 2026

Under the influence of continued high pressure, VFR conditions will prevail through the period. The pressure gradient will begin to tighten Wednesday, leading to a slight increase in wind speeds to around 10 knots at most terminals.

MARINE

Issued at 1250 PM CDT Tue Sep 29 2026

Onshore flow will become dominant again today around around 10 knots. As the week progresses, the pressure gradient will tighten causing winds to begin 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.