textproduct: New Orleans/Baton Rouge

KEY MESSAGES

Updated at 111 PM CDT Sat Jul 11 2026

- The potential for heavy rainfall and localized flash flooding will increase Sunday and peak Monday as a slow-moving frontal boundary approaches from the north. Additional heavy rainfall remains possible Tuesday.

- A drier pattern is expected late next week into next weekend. The primary concern will then shift toward increasing heat, with heat indices potentially approaching advisory criteria.

SHORT TERM

(Now through Tuesday night) Issued at 111 PM CDT Sat Jul 11 2026

The upper ridge that was recently extended across much of the southern CONUS continues to retreat westward, while heights gradually fall along its eastern periphery. A mid-level trough digging into the southeastern states tonight through Monday will establish a weakness over the region and help drive a weak surface boundary southward toward the northern Gulf Coast.

The typical summertime convective cycle is already underway today. Convection over the coastal waters has generally followed the expected weakening trend, with development transitioning inland along the sea breeze and other mesoscale boundaries. Coverage has become more widespread than during previous days. Thunderstorms should continue through the afternoon before diminishing this evening with the loss of daytime heating.

The most recent 12Z KLIX sounding depicts a fairly typical summertime moisture profile supportive of efficient rainfall production, with precipitable water near the daily mean of 1.8". A modest mid level dry layer and DCAPE near 800 J/kg could allow stronger storms to produce gusty, generally sub-severe winds. Mean storm motion will be roughly from south to north, although cold- pool outflows and interactions with other boundaries will produce more variable and occasionally deviant motion. Locally heavy rainfall is possible, but the overall flooding threat today should remain localized.

Convective coverage should increase further Sunday as the ridge continues to weaken and the approaching trough provides somewhat greater large-scale support. The southward-moving surface boundary, sea breeze and remnant outflow boundaries will provide several potential initiation points. The airmass will also become increasingly moist, with precipitable water values rising above 2 inches. Locally heavy rainfall will be possible wherever storms repeatedly develop or move across the same locations. Placement of the heaviest rainfall will remain dependent on mesoscale boundaries and is unlikely to be resolved well in advance. The general evolution should favor the highest POPs near coastal areas earlier in the day, expanding inland and into southern Mississippi during the afternoon.

The greatest heavy-rain concern during the forecast period continues to be Monday as the upper weakness and surface boundary settle closer to the area. A deeply moist airmass, with precipitable water values potentially approaching the daily maximum near 2.4 inches, will combine with weak steering flow and multiple low-level convergence boundaries. This setup will favor slow-moving storms, backbuilding and localized training. Widespread rainfall totals of 1 to 3 inches are forecast through early next week, but localized amounts exceeding 5 inches will be possible where repeated convection occurs. These higher totals could produce rapid ponding, flooding of low-lying and poorly drained locations, and localized flash flooding.

Confidence is high that numerous thunderstorms will produce pockets of heavy rainfall Monday, but remains considerably lower regarding the location of the heaviest rainfall axis. Current indications generally favor areas near and south of the I-10 corridors, but meaningful shifts remain possible as the locations of mesoscale boundaries become better established.

Numerous showers and thunderstorms may continue into at least part of Tuesday while the upper weakness remains nearby. The heavy-rain threat will increasingly depend on Monday's rainfall footprint and the location of any lingering boundaries. Areas receiving substantial rainfall Monday would be more susceptible to additional flooding Tuesday, even if rainfall rates or overall coverage begin to decrease. Greater cloud cover and more frequent convection should hold daytime temperatures below recent levels Monday and Tuesday, with highs generally remaining below 90 degrees.

MEFFER

LONG TERM

(Wednesday through Friday night) Issued at 111 PM CDT Sat Jul 11 2026

The mid-level weakness should begin moving away from the northern Gulf Coast Tuesday night into Wednesday as ridging gradually rebuilds from the northwest. Surface high pressure is also expected to become more established across the region. This evolution should bring lower PW regime and a transition from numerous thunderstorms to more isolated/scattered, primarily diurnal convection Wednesday and Thursday. The heavy rain threat should then diminish considerably, although any slow-moving storm could still produce a localized downpour.

The upper ridge is forecast to become more influential over the local area Friday into next weekend. Increasing heights from the Gulf across the CWA to the Central Plains, few (if any) thunderstorms and greater insolation should allow temperatures to climb back into the lower and middle 90s. With higher surface moisture remaining in place that keeps dewpoints in the mid/upper 70s, heat index values will also rise. At this time, confidence is greater in a warming trend than in temperatures or heat indices reaching any specific value. The strength and placement of the ridge will determine how much convection is suppressed and how quickly heat stress increases. A stronger ridge centered closer to the Lower Mississippi Valley would support hotter conditions, while a ridge remaining farther west would permit somewhat greater afternoon storm coverage and limit the heat moreso. Regardless, may be looking at heat advisories for at least local urban areas Friday thru weekend.

MEFFER

AVIATION

(18Z TAFS) Issued at 111 PM CDT Sat Jul 11 2026

VFR conditions should prevail outside of convection through the period. Ceilings have generally lifted with daytime heating. However, thunderstorm coverage has been increasing as expected this afternoon, and PROB30 groups at all TAF sites. Any direct impact could briefly produce IFR visibility in heavy rain, gusty and variable winds, and frequent lightning. Convection should diminish this evening, with light winds overnight. Additional coastal convection may develop late tonight into Sunday morning, so do have some concern that PROB30 or TEMPO may be needed for KHUM, KMSY and KNEW. Greater impacts from rain/storms Sun aftn thru Monday for all terminals as weak frontal boundary drifts south into the region.

MEFFER

MARINE

Issued at 111 PM CDT Sat Jul 11 2026

The Bermuda ridge extending into the Gulf will generally support light to occasionally moderate onshore flow through Sunday morning. An upper trough moving into the southeastern United States will bring a weak frontal boundary toward the coastal waters before it stalls. Winds should weaken as the pressure gradient relaxes, resulting in generally benign wind and sea conditions.

The primary marine hazards will come from thunderstorms, with the greatest coverage generally expected during the overnight and morning hours over the open Gulf waters. Storms will be capable of frequent lightning, locally higher waves and sudden wind gusts. Waterspouts will also remain possible, particularly near developing early- morning convection.

MEFFER

LIX WATCHES/WARNINGS/ADVISORIES

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