textproduct: New Orleans/Baton Rouge

KEY MESSAGES

Updated at 620 PM CDT Wed Sep 9 2026

- Another surge of tropical moisture will elevate the risk for locally heavy rainfall leading to street flooding and overflowing of poor drainage areas Thursday through Saturday.

- A few storms could be strong to severe each day, especially on Friday and Saturday. The primary hazards will be locally damaging winds, small hail, and frequent lightning.

SHORT TERM

(Now through Saturday night) Issued at 106 PM CDT Wed Sep 9 2026

Scattered showers and storms in association with a weak tropical wave in the northern Gulf continue to spread westward along coastal Louisiana today. Though some additional pop up thunderstorm activity will possible mainly south of the I-10 corridor this afternoon, drier southern Appalachian air from a dissipating backdoor front is mixing into northern areas. Today's PoPs will be at their lowest for the week as a result.

The tropical wave will continue to move west under the influence of the surface high situated over the Carolinas on Thursday bringing with it a surge in tropical moisture (PWAT >90th percentile). Enhanced sfc convergence in addition to this moisture will support scattered to widespread marine convection through the early morning hours on Thursday which will be more inclined to move inland after sunrise. Land areas will gradually destabilize into late morning and scattered showers and storms will gradually push westward, farther inland. With high PWATs and the potential for training band structures, locally heavy rainfall leading to flooding of streets and poor drainage areas will be possible.

These elevated heavy rainfall parameters will persist into Friday and even Saturday as the tropical wave slows and turns north, rounding the surface high. Mid-upper air atmospheric conditions will also improve with lowering of heights as a weak shortwave trough moves across the lower Mississippi River valley. Coupled with the lingering higher PWATs (>90th percentile), this will allow for increased convective activity and efficient rainfall rates (2-3" per hour) especially during the midday to afternoon period. The additional mid-upper forcing will also allow for a few of these storms to grow taller and stronger, so a few strong to severe thunderstorms are probable with the primary hazards being locally damaging winds via downbursts, small hail, and frequent lightning.

Deep tropical moisture in combination with high temps still reaching the low to mid 90s (slightly above normal) will keep heat indices elevated into the low 100s when the sun is out especially around the midday timeframe. However, elevated heat risk will be limited by storm coverage so heat headlines are not expected at this time.

LONG TERM

(Sunday through Tuesday night) Issued at 106 PM CDT Wed Sep 9 2026

Tropical moisture will linger into Sunday as the shortwave trough begins to break down and lift out. Thereafter, PoPs will gradually decline into early next week as mid-upper ridging and subsequent high pressure expand and dominate the southeastern CONUS. High temps will remain slightly above normal and heat indices will creep closer to 105-110 degrees for parts of Southeast Louisiana. However, daily afternoon rainfall chances remain in the forecast at this time which would be the primary area of uncertainty regarding higher heat risk. Global model ensemble guidance favors this elongated southern CONUS ridge staying overhead through much of next week though the Week 2 ensemble guidance indicates that this pattern could transition toward an eastern CONUS troughing pattern more favorable for at least decaying frontal passages into next weekend.

AVIATION

(00Z TAFS) Issued at 620 PM CDT Wed Sep 9 2026

VFR conditions at all terminals now and will continue through the early morning hours. Moisture spreading inland from offshore at that time will bring scattered convection and associated lowered CIG and VIS with terminals impacted being HUM/MSY/ASD/GPT and covered by PROB30 coding. Daytime hours tomorrow will see higher chances and related impacts from sh/ts activity.

MARINE

Issued at 106 PM CDT Wed Sep 9 2026

Easterly winds around 15 knots are expected over the waters east of the Mississippi River today as a weak tropical wave slides through the Gulf. These higher winds will push wave heights to 2 to 3 feet over the eastern waters and create choppy seas. Diurnally driven storms in the early morning hours will be capable of locally higher winds and seas and waterspouts. As the wave slides to the west on Thursday and Friday, high pressure will build back over the waters. Winds will turn southerly and fall back to 5 to 10 knots as the high over the eastern Gulf expands to the west. Seas will also fall to 1 to 2 feet as the winds decrease. These conditions will generally persist through the upcoming weekend.

LIX WATCHES/WARNINGS/ADVISORIES

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