Marine Weather and Tide Forecast for Laplace, LA

LONG TERM
(Wednesday night through Monday)
Issued at 1144 AM CDT Tue Jul 15 2025

Wednesday evening through the weekend, rain chances will be enhanced thanks to the increase in Gulf moisture from the disturbance moving west across the northern Gulf. NHC has a 40% chance of development for this system in the next 7 days.
Regardless of development, heavy rainfall and flash flooding will be the main threat with this system. Generally, the environment is quite conducive for flash flooding with long skinny CAPE, abundant moisture throughout the atmospheric column and fuel source, high PWs around 2.2 inches or greater, low shear, etc.
Additionally, some of the models are hinting at parallel flow in the vertical column, which could be a big concern for training.
These storms will have the potential for Looking at recent model guidance, we are forecasting widespread 3 to 6 inches of rainfall with locally higher amount up to 10 inches possible. This rainfall will also be highly efficient with rainfall rates in excess of 2 to 4 inches per hour likely.

Numerous rounds of rainfall will begin off and on Wednesday night through Saturday with the bulk of the rainfall occurring Thursday and Friday. Right now, there is still a lot of model uncertainty as it pertains to the location of the highest rainfall threat and totals. While this has been fluctuating somewhat, WPC has outlined our westernmost areas on Friday as being in a Moderate Risk (level 3 out of 4) for flash flooding, including the Baton Rouge metro and the Atchafalaya Basin. Given some of the lingering uncertainties, would not be surprised to see this adjusted or expanded in the next 1-2 days. A Flood Watch has been issued to account for this risk of flash flooding. It starts at 18z Wednesday and runs through 00z Saturday for now to highlight the days with the greatest threat, but it could be extended in time further as we get closer to the weekend. It is worth noting that any changes to the track of the disturbance west or east could have a major influence on the locations with the heaviest rainfall.

In terms of the impacts, they could be quite significant, especially Friday, depending on the track of the system. While widespread minor to moderate street flooding, impassable roads, etc. will possible, it is not outside the realm of possibility that we could see more significant localized flooding, especially in urban/vulnerable areas like Baton Rouge, the MS Coast, or even New Orleans. It will highly depend on how the system develops and moves over the next 1-2 days. We especially want to emphasize the worst case scenario (i.e. the highest potential) that we could see from this event. While we have low confidence in the location of the greatest flash flooding impacts, we have medium to high confidence that someone will see those locally higher totals up to 10 inches and significant flooding in our area. The key, as always in Southeast Louisiana and Coastal Mississippi, is where it falls and how quickly. If the higher rainfall totals fall in the Atchafalaya Basin or west, the impacts will be much less concerning. If the higher rainfall totals fall in any urban areas (Baton Rouge, New Orleans, MS Coast) or train multiple times over rural areas, this could cause significant concerns.

Another point we wanted to mention was that a lot of the models have been showing a dry overnight bias that seems unrealistic.
There will still be medium to high (60-80%) chances of heavy rainfall and flooding overnight, similar to the daytime hours. As a result, extra caution should be used if you will be planning to drive at night, since depth of water and any flooding will be impossible to see at night.

This event could be a quite significant rain producer for our area and with so much uncertainty in the location of the heaviest rainfall, it is important to prepare now, while there is still time. Clean out those ditches and catchbasins and make a plan now ahead of time for the potential for flash flooding. MSW

AVIATION
(18Z TAFS)
Issued at 1144 AM CDT Tue Jul 15 2025

VFR conditions prevail at all area airports and will persist through the forecast period. Afternoon and evening showers and storms are possible, so TEMPO groups are in effect to reflect these conditions briefly dropping to MVFR as a result. MSW

MARINE
Issued at 1144 AM CDT Tue Jul 15 2025

Benign conditions will continue through the next few days as high pressure remains overhead or at least nearby. Winds generally onshore at 10 knots or less with seas under 2 feet. The only exception would be brief gale force wind gusts from isolated storms. A broad area of low pressure moving into the northeastern Gulf later this week will increase winds/seas over local waters, especially Thursday through the weekend. MSW

PRELIMINARY POINT TEMPS/POPS
MCB 73 96 73 90 / 10 30 40 90 BTR 76 95 76 90 / 10 40 40 90 ASD 75 95 73 88 / 10 60 70 100 MSY 80 94 78 89 / 10 60 70 100 GPT 77 96 75 88 / 10 70 70 100 PQL 76 95 74 89 / 20 70 70 90

LIX WATCHES/WARNINGS/ADVISORIES
LA...Heat Advisory until 7 PM CDT this evening for LAZ034>037-039- 046>048-056>060-064-065-070-071-076>090.

Heat Advisory from 10 AM to 7 PM CDT Wednesday for LAZ034>037- 039-046>048-056>060-064-065-070-071-076>090.

Flood Watch from Wednesday afternoon through late Friday night for LAZ034>037-039-046>048-056>060-064>071-076>090.

GM...None.
MS...Heat Advisory until 7 PM CDT this evening for MSZ068>071-077- 083>088.

Heat Advisory from 10 AM to 7 PM CDT Wednesday for MSZ068>071- 077-083>088.

Flood Watch from Wednesday afternoon through late Friday night for MSZ077-083>088.

GM...None.