textproduct: New Orleans/Baton Rouge

KEY MESSAGES

Updated at 617 PM CDT Tue May 19 2026

- Low confidence high impact forecast tonight with the possibility of flash flooding across northwestern portions of the CWA. This includes the cities of Baton Rouge and McComb.

- Showers and thunderstorms will become more numerous and widespread Wednesday through the weekend. 7 day rainfall totals will range from 4 to 7 inches in the northwest to less than an inch of much of coastal MS and extreme SELA.

- Minor coastal flooding may slightly impact typically known problem areas like Waveland, MS today and Wednesday around midday.

SHORT TERM

(Now through Wednesday) Issued at 256 PM CDT Tue May 19 2026

The short term forecast is going to focus on the remainder of this afternoon, evening and then look at tomorrow but probably a little more focus on the next 6-12 hours than normally with the regular package. Some of the CAMs for the past 24 to even 30 hours have consistently focused on the northwestern quadrant of our CWA developing convection during the late afternoon through the evening hours. This is remarkable consistency given that they have been very inconsistent with any MCS or remnants of an MCS moving into the area overnight tonight.

The convection of concern would begin to develop around 21/22z and is well ahead of any MCS. The big question is why would this develop and develop over the areas mainly near and northwest of a line from Baton Rouge to McComb. A few things look like they could be coming together. First models are suggesting that even though the LL winds don't necessarily increase but there will be a decent increase in the LL confluence across the northwest starting around 22z and persisting through the evening or until an MCS or remnant boundary of an MCS moves through overnight. There is already a mid lvl impulse pushing into the Lower MS Valley and it is already adding to the lift giving us isolated to widely scattered showers across the western half of the CWA. There is also a remnant boundary from an MCV that was over southeast TX earlier today moving towards the Atchafalaya and that could help to spark some development across the northwest in the next few hours. Last we will see an increase in the diffluence aloft at the same time we are seeing that increase in the LL confluence. In almost a classic split flow type setup, the northwestern portions of the CWA will be directly under an enhanced V which will provide very efficient diffluence aloft.

Looking at the current conditions there is abundant moisture in place. PWs are ranging from 1.7 to just under 1.9" based off of GOES19 TPW product. LL moisture has also been increasing for the past 24 to 36 hours and dewpoints are in the lower to mid 70s. Instability is also not in short supply with ML CAPE of 2500 and sfc based CAPE between 3-3500 j/kg however the Mid lvl lapse rates are likely around 5.5-6 C/km which this makes sense given the moisture laden airmass we have. This also would tend to take hail off the board from a standpoint of severe aspects. I won' t say tornadoes are not possible but they aren't the top concern given the lack of shear. 0-1 and 0-3 km helicity is absent basically and 0-6km bulk shear is generally around 20-30kt. This suggest more multicellular setup and not really organized severe weather. That said with the amount of moisture and instability in place there will be a risk possibly a wet microburst or two with any thunderstorm that can become a little more potent. So at this time severe can not be ruled out but it is not the biggest concern, that may actually be flash flooding but it will be highly dependent on where the storms fire and of course if we actually get deeper convection to persist for the 4 to 8 hours that some of the CAMs are advertising.

At this time confidence is still in the medium range mainly do to convection developing, how long it persists, and especially location. That said confidence is high that any thunderstorms that develop late this afternoon and through the evening will be extremely efficient due to weak steering currents, abundant moisture and instability, and enhanced diffluence aloft. The REFS PMM shows widespread totals greater than 4 inches across much of the northwest with multiple locations possibly seeing greater than 7 inches and that is before 12z tomorrow. The majority of this risk looks to be from 22z till 4z today/tonight but storms could persist longer and there is still a great deal of uncertainty with respect to any MCS developing and trying to move towards the area overnight. Biggest concern is if storms get anchored in and around the BTR metro (includes Denham Springs, Walker, Baker, portions of West Baton Rouge) or some of the flashier parts of southwest MS where there is some elevation changes and could lead to some very problematic flash flooding.

As for overnight and tomorrow this is more of a question mark. It looks like a disturbance coming out of Mexico may be what helps get another MCS to develop over southeast TX this evening and that will try to work east. This lift may also try to help redevelop a decaying MCS moving south and SSE out of northeast TX and southwest AR. There is a lot of uncertainty with how all that develops and move into the region. If it strengthens and develops a strong cold pool it would surge SSE towards the instability and likely moves into or skirts the western fringes of the CWA and into the Gulf early tomorrow...probably before sunrise. However there will be some remnant boundary stretching back to the north from it across the CWA which may be the focus of development tomorrow. The biggest question is how much cloud cover do we have over the area and will it allow us to destabilize enough to get convection to develop early enough or does it hold off and we wait for the next subtle impulse to come across the area in the southwest flow aloft tomorrow afternoon/evening. /CAB/

LONG TERM

(Wednesday night through Monday night) Issued at 256 PM CDT Tue May 19 2026

Focus is really on the short term especially given the next 4 to 8 hours and uncertainty overnight. That said models have not changed and the pattern we will be in just screams active weather for the next week. Obviously rain won't be occurring the entire time as there will be breaks and possibly even one or two days with limited rainfall as timing any of these impulses is difficult to futile this far out and depending how long one rain event lasts it could work us over pretty well leading to the area needing some time to recover. No deviations made from the latest NBM.

As we have been mentioning for the last few days, we will remain under persistent southwest flow aloft with abundant moisture in place. This is going to leave us in a rather favorable regime for multiple rounds of storms and locally heavy rain. Biggest difference the previous rain event we have had and is a positive difference is there is no real well defined front laying up over the area to act as a sfc/LL focus. That said with the ridge still holding strong over the eastern Gulf and into the southeastern CONUS and southwest flow aloft we still look like there could be quite the dichotomy across the region with the northwest seeing multiple inches of rain, 3-6 inches after tonight and tomorrows possible rain and maybe struggling to even get an inch of rain over portions of coastal MS and extreme southeast LA. Temperatures will be slightly above normal mainly due to above normal lows as we remain very humid throughout the forecast. /CAB/

AVIATION

(00Z TAFS) Issued at 621 PM CDT Tue May 19 2026

VFR/MVFR conditions through the cycle with a couple of opportunities for convective development. First will be overnight for the western half of the area as a decaying line of storms moves closer to those terminals. Additional convective development will be possible Wednesday afternoon and evening. If convection moves over a terminal there will be a bit more erratic winds as well as IFR or perhaps lower in the heaviest rainfall. Otherwise, winds will remain light to moderate from the south. (Frye)

MARINE

Issued at 256 PM CDT Tue May 19 2026

A large area of high pressure will remain situated over the western Atlantic through the week and into the weekend. This will maintain light to moderate onshore flow through the time. Winds will bounce around headline criteria with sustained winds right around to slightly below 15 kts, especially closer to the coast and west of the MS River. As for showers and thunderstorms, daily isolated to scattered showers will be possible each day however the bulk of the coverage will remain inland. With any thunderstorms locally hazardous winds and waves can be expected.

Any minor coastal flooding that occurred today should quickly abate and expecting tides to be a little lower each day through the remainder of the week and into the weekend. /CAB/

LIX WATCHES/WARNINGS/ADVISORIES

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