textproduct: New Orleans/Baton Rouge

KEY MESSAGES

Updated at 148 PM CDT Mon Aug 17 2026

- Dangerous heat continues with afternoon heat indices commonly reaching 110115F. Warm overnight temperatures will offer limited relief.

- Only isolated to scattered afternoon storms are expected the next couple days. Coverage should be somewhat greater toward the Mississippi coast and eastern portions of the forecast area.

SHORT TERM

(Now through Thursday night) Issued at 148 PM CDT Mon Aug 17 2026

Heat remains the primary forecast concern through the short term as a broad mid/upper-level ridge centered near the Four Corners continues to be extend eastward across the Lower Mississippi Valley and Gulf Coast. The local area remains within the eastern periphery of the ridge rather than beneath its strongest subsidence, which will allow at least some convection each afternoon. However, the combination of a warm low/mid-level thermal profile, generally weak west to northwest low-level flow, and limited large-scale ascent will continue to favor well above normal temperatures and only modest convective relief. With little thermal profile change for Tuesday, have issued an Extreme Heat Warning for the Mississippi Coast and Louisiana parishes around Lake Pontchartrain...Heat Advisory elsewhere.

Isolated to scattered convection will be possible this afternoon along the sea breeze, lake breeze and any differential-heating boundaries. Coverage should be somewhat greater across the Mississippi coast and eastern portions of the forecast area, where the influence of the upper ridge is weaker, with lower coverage farther west toward Baton Rouge and the Atchafalaya Basin. POPs generally in the 20 to 40 percent range appear reasonable through mid week, highest east. Any storm will be capable of briefly knocking temperatures down considerably, but the localized nature and relatively late timing of convection will provide little area- wide relief from the heat. A few storms could also produce brief gusty winds given the dry air noted aloft.

By Wednesday and Thursday, troughing digging southward across the eastern United States should begin to erode the eastern side of the upper ridge. The change is gradual rather than abrupt, so substantial cooling is not expected immediately. However, slightly lower heights, a little more moisture and increasing opportunities for mesoscale boundaries should support a modest upward trend in afternoon convection. This should begin to shave a degree or two off daytime temperatures in some areas, particularly across the eastern half of the CWA and near the coast. Interior western portions of the area will likely remain the hottest and driest.

LONG TERM

(Friday through Sunday night) Issued at 148 PM CDT Mon Aug 17 2026

The broad-scale pattern becomes somewhat less favorable for persistent excessive heat in the later half of the week and over the weekend as the eastern portions of the Four Corners ridge is eroded by an eastern U.S. trough. This should gradually weaken the ridge aloft locally and allow somewhat greater convective coverage compared with the first half of the week. For this reason, a completely flat temperature forecast through late week into the weekend appears less likely than at least modest cooling. Heat indices around or above 108 degrees will become more and more confined to areas near the coast where daytime dewpoints hold a bit better than those farther inland that are able to mix out better.

By Saturday and Sunday, a combination of slightly lower mid-level heights, increasing clouds and a somewhat better chance of afternoon convection should trim daytime highs by a few degrees in at least portions of the area. Rain chances should trend upward into the chance category for more of the area Friday thru Sunday, with the greatest coverage generally favored across the eastern and coastal portions of the CWA. Not looking at widespread convection and substantial day-to-day variability will remain dependent on mesoscale boundaries and the evolution of the weakness over the eastern Gulf.

That eastern Gulf feature, which is at the base of the trough over the eastern US, is also the primary source of uncertainty for the weekend. A farther west evolution would produce greater rain coverage, more cloud cover and a more noticeable reduction in afternoon temperatures. If it instead remains east of the area and is absorbed into the larger eastern U.S. trough, stronger ridge influence would linger locally and temperatures could remain on the warm side of guidance. At this time, a gradual increase in convection and modest reduction in afternoon heat appears to be the most reasonable middle ground rather than either a major pattern change or uninterrupted extreme heat through the entire weekend.

MEFFER

AVIATION

(18Z TAFS) Issued at 148 PM CDT Mon Aug 17 2026

VFR conditions will dominate the forecast outside of convection. Isolated to scattered thunderstorms are possible during the afternoon, with the greatest potential at eastern and coastal terminals. Direct impacts remain too localized for prolonged restrictions, but any terminal affected by a storm could briefly experience IFR visibility in heavy rainfall along with gusty and variable winds. Convection should diminish during the evening with mainly VFR conditions overnight. A similar pattern is expected Tuesday.

MEFFER

MARINE

Issued at 148 PM CDT Mon Aug 17 2026

Surface high pressure centered over the central Gulf will maintain a generally weak pressure gradient through much of the period. A predominantly westerly flow regime will continue, with a typical summertime diurnal fluctuation in both direction and speed. Winds should generally increase during the overnight and early morning hours to around 10 to 15 knots before relaxing to around 5 to 10 knots during the late morning and afternoon. Nearshore winds may become more southwesterly during the afternoon as the sea breeze develops. Seas over the open waters will generally be around 2 to 3 feet during the stronger nighttime flow and closer to 2 feet or less during the day, with considerably lower wave heights across the tidal lakes and protected waters. Isolated thunderstorms will remain possible, particularly during the overnight and early morning hours over the coastal waters and nearer the coast during the afternoon. Locally higher winds and seas along with frequent lightning will be possible near any thunderstorm.

MEFFER

LIX WATCHES/WARNINGS/ADVISORIES

LA...Extreme Heat Warning until 8 PM CDT this evening for LAZ034>037- 039-046>048-056>058-064-070-071-076>087-089>100.

Heat Advisory from 11 AM to 8 PM CDT Tuesday for LAZ034>037-039- 046>048-056-070-071-090-091-093>097.

Extreme Heat Warning from 11 AM to 8 PM CDT Tuesday for LAZ057- 058-064-076>087-089-092-098>100.

GM...None. MS...Extreme Heat Warning until 8 PM CDT this evening for MSZ068>071- 077-083>088.

Heat Advisory from 11 AM to 8 PM CDT Tuesday for MSZ068>071-077.

Extreme Heat Warning from 11 AM to 8 PM CDT Tuesday for MSZ083>088.

GM...None.