textproduct: New Orleans/Baton Rouge

KEY MESSAGES

Updated at 136 PM CDT Sun Sep 20 2026

- Hot conditions will persist through much of the week, with highs near records thru mid week and generally above normal thru next weekend.

- Rain chances will be highest Monday into Tuesday, but rain amounts will generally be less than one half inch this week as not much rain is expected for the remainder of the forecast period.

SHORT TERM

(Now through Wednesday night) Issued at 136 PM CDT Sun Sep 20 2026

Upper ridging remains the dominant influence across the region this afternoon, although that high centered over east Texas continues to gradually weaken. A weak upper disturbance that was over the eastern Gulf yesterday hasn'te moved any. At the same time, additional shortwave energy is progressing eastward across the Northern and Central Plains. At the surface, broad high pressure extends across much of the Southeast and northern Gulf Coast, keeping the local pressure gradient weak. In local terms, strong subsidence beneath the ridge aloft will continue to suppress convection across nearly the entire area. The main exception will be in southern Mississippi and adjacent coastal waters where an old outflow boundary from convection to the east may provide just enough low-level convergence for an isolated afternoon shower or thunderstorm. Visible satellite imagery from the last hour does show some CU enhancement which may be the start of isolated convection. Should be noted that it would be more inland than CAMs suggest. Otherwise, mostly sunny skies will allow temperatures to climb into the lower to middle 90s, with a few upper 90s possible across the northwest portion of the CWA. Increasing boundary-layer moisture will result in heat indices reaching the lower to middle 100s, locally as high as around 106, just shy of the 108 degree Heat Advisory threshold.

A somewhat more noticeable change develops Monday as the upper ridge weakens further and a shortwave currently moving through the central Plains approaches the Mid Mississippi Valley. At the same time, low- level moisture will continue to increase across the area. The combination of less subsidence, increasing column moisture, daytime instability, and weak mesoscale boundaries should support scattered afternoon showers and thunderstorms. Convective coverage should initially favor coastal seabreeze boundaries before spreading inland during peak heating. Current guidance continues to suggest the highest probabilities from the Mississippi coast westward into the Northshore and coastal southeast Louisiana, while locations farther northwest toward Baton Rouge and southwest Mississippi may see considerably less activity. The weak flow through much of the column will result in slow-moving, pulse-type convection. Locally heavy rainfall possible beneath stronger cells, but limited overall coverage and a lack of a persistent focusing boundary should keep the flooding threat low. Monday will otherwise remain hot, with highs generally in the lower to middle 90s and perhaps upper 90s near Baton Rouge. Increasing dewpoints will again allow peak heat indices to reach the mid to upper 100s. Cloud and precipitation coverage should limit both the spatial extent and duration of the highest heat indices.

The shortwave to the north will shift east of the region Monday night into Tuesday while upper ridging begins rebuilding eastward from Texas into western Louisiana. This will begin to increase subsidence again, but enough residual moisture should remain for isolated afternoon convection Tuesday, particularly across eastern and coastal portions of the forecast area. Coverage should be lower than Monday, with most locations remaining dry. Temperatures will remain well above normal with highs generally in the lower to middle 90s and upper 90s possible.

MEFFER

LONG TERM

(Thursday through Saturday night) Issued at 136 PM CDT Sun Sep 20 2026

Confidence continues to increase that upper ridging will rebuild across the Lower Mississippi Valley during the middle and latter portions of the week. This is a notable change from guidance a few days ago, which had suggested a stronger eastern CONUS trough would suppress the ridge farther west and allow a wetter pattern to develop. By Wednesday, the northern-stream shortwave will be progressing toward the Ohio Valley while the ridge expands eastward from Texas across Louisiana. Some lingering low-level moisture may still support an isolated afternoon shower or thunderstorm, mainly near the coastal areas, but increasing subsidence should quickly reduce convective coverage.

The ridge becomes increasingly dominant Thursday into Friday with mainly dry conditions expected. However, the developing eastern U.S. trough and surface high pressure building southeastward behind it should allow a more persistent northeasterly low-level flow to develop across the local area. This should gradually advect somewhat drier air into southeast Louisiana and southern Mississippi despite continued ridging aloft. Temperatures will consequently remain above normal through mid, with highs mainly in the lower to middle 90s Wednesday. A gradual downward trend in temps is expected Thursday through Saturday as the drier northeasterly flow strengthens. Highs should trend toward the upper 80s to lower 90s by Friday and Saturday across much of the area. Overnight temperatures should also begin responding to the drier air late in the week, with lows eventually falling into the middle and upper 60s across southwest Mississippi and portions of the Florida Parishes, while remaining in the lower to middle 70s closer to the Southshore. Confidence is reasonably high in a predominantly dry late-week pattern. The primary uncertainty remains the exact strength and eastward extent of the upper ridge and how aggressively the eastern trough can drive lower dewpoints southward into the region.

MEFFER

AVIATION

(18Z TAFS) Issued at 136 PM CDT Sun Sep 20 2026

VFR conditions are expected to prevail through the period with mid level CU field spreading across the area thru the next several hours. Isolated convection is possible, but probs too low to have any mention in TAFs. If any showers do develop, more likely terminals to be impacted would be KGPT, KASD, and maybe KHDC. Winds will be light and variable for the majority of the next 24 hours.

MEFFER

MARINE

Issued at 136 PM CDT Sun Sep 20 2026

Broad surface high remains close to the northern Gulf Coast, maintaining a weak pressure gradient and generally benign marine conditions. Weakening subsidence aloft has allowed for some convection over the open Gulf waters this afternoon but coverage is quite isolated. Winds will remain light and somewhat variable nearshore, becoming more consistently onshore during the afternoon with the sea breeze. Convective coverage will increase Monday as deeper moisture returns and upper-level subsidence further weakens. Any thunderstorm could briefly produce locally higher winds and seas, frequent lightning, and reduced visibility, but widespread marine hazards are not expected.

High pressure will remain close enough to the region through Tuesday to maintain generally light winds. A more persistent northeast to east flow should develop Wednesday through the latter part of the week as surface high pressure builds southeastward across the eastern United States. At this time, winds and seas are still expected to remain below headline criteria.

MEFFER

LIX WATCHES/WARNINGS/ADVISORIES

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