textproduct: New Orleans/Baton Rouge

KEY MESSAGES

Updated at 939 PM CST Thu Dec 4 2025 1. A widespread area of 2-4" of rainfall has been measured over the past 24 hours along the I-10/12 corridor. A slightly higher swath of 5-6" of rainfall exists along a line from Morganza, LA east through Amite, LA and to Saucier, MS. Coastal Louisiana and Southwest MS received lower totals of 0.5" to 2.5" during this period.

2. The slow-moving frontal boundary associated with the coastal low is progressing southeastward and will clear land areas through the morning hours. Drier air filtering in will lower rainfall rates and reduce the risk for excessive rainfall and flash flooding on Friday. Additional rainfall of up to 3" could occur mainly along and east of the I-55 corridor, near the coast. However, most areas are likely (>60%) to see between 0.5" and 1.5" of additional rainfall with scattered shower activity Friday through Saturday.

3. Another shot of colder air will come from a stronger cold front late on Sunday. Colder air from this front won't arrive until Monday so the coldest night of the forecast period will see temperatures near freezing in southwest MS and adjacent parishes on Tuesday morning.

SHORT TERM

(Tonight through Saturday night) Issued at 939 PM CST Thu Dec 4 2025

Southeasterly surface winds are beginning to flip northerly across the I-10/12 corridor indicating the passaging of a weak frontal boundary in association with the coastal trough of low pressure scooting east along the northern Gulf coast. Shower activity is finally tapering off as this frontal boundary pushes southeast. Weak shower and misty, low-stratus conditions will continue through the overnight hours, but a lull in rainfall is expected through the most of the morning. Drier air aloft will gradually filter in behind this front causing PWATs to drop from daily max levels down closer to the 75-90th percentile. This will reduce the efficiency of rainfall rates and consequently reduce the risk of flash flooding over the area on Friday and Saturday.

PWATs will remain elevated (~1.5") near the coast as the frontal boundary stalls out and southwest flow aloft persists into the weekend. Another weak shortwave within the longwave flow will help to kick up more convective activity later on Friday morning and into with the heaviest rainfall likely to occur near the coast. An additional round is likely to develop beyond this wave as we head into Saturday which will likely be the final round before the shortwave finally pushes through. Additional rainfall will be lighter especially farther inland, but NBM guidance points to some areas receiving upwards of 1.5 to 2" of additional rainfall along and east of the I-55 corridor, closer to the coast where PWATs are higher through Saturday. However, rainfall rates should remain limited enough to mitigate the flash flood risk.

LONG TERM

(Sunday through Thursday night) Issued at 939 PM CST Thu Dec 4 2025

The longwave trough situated over the central CONUS will gradually propagate east and lift out allowing for southwest flow aloft to become northwesterly and pushing a stronger frontal boundary and a colder air mass through the area on Sunday and into Monday. This will not only notably dry things out areawide, but also bring near freezing temperatures to southwest MS and adjacent Louisiana parishes. Surface high pressure will dominate early next week, but it may not last long before another shortwave dives out of the northern Great Plains, following the northwest flow aloft. Global model guidance remains in some disagreement pertaining to the timing and depth of this shortwave trough which will determine whether a substantive frontal boundary increases PoPs and breaks down surface high pressure by later in the week.

AVIATION

(06Z TAFS) Issued at 939 PM CST Thu Dec 4 2025

SHRA has gradually tapered off from west to east, but IFR CIGs will linger through the overnight hours. Winds have switched to northerly at all terminals in response to a frontal boundary passage which is progressing offshore tonight. Another round of -SHRA begins midday Friday and will spread from southwest to northeast across the area. Some areas closer to the coast could see some TSRA conditions, but this should remain south of all terminals. Onset appears to be closer to 1800 UTC and will persist into the overnight hours on Friday night. Have introduced these SHRA lines to the end of the forecast cycle to depict latest forecast timing at respective terminals.

MARINE

Issued at 939 PM CST Thu Dec 4 2025

Winds will relax and return to offshore late Friday post-frontal passage and then more variable on Saturday with the passage of another weak sfc low. A stronger frontal passage on Sunday night will bring another push of strong offshore winds on Monday which could prompt small craft headlines for much of the coastal waters.

With the wind direction being primarily out of the east, minor coastal flooding is expected mainly for St. Bernard, eastern Orleans, southeastern St. Tammany parishes, as well as coastal Hancock and Harrison counties on Friday morning. Subsequent forecasted tide cycles appear elevated but will be lower than Friday so no additional headlines appear to be warranted for this weekend at this time.

PRELIMINARY POINT TEMPS/POPS

MCB 50 41 48 42 / 100 70 50 30 BTR 54 42 50 45 / 100 60 40 40 ASD 57 44 55 44 / 90 80 50 60 MSY 61 50 56 50 / 90 70 50 60 GPT 57 46 56 47 / 90 90 50 60 PQL 58 44 57 45 / 90 90 50 60

LIX WATCHES/WARNINGS/ADVISORIES

LA...Coastal Flood Advisory until 6 AM CST Friday for LAZ070-076-078.

GM...None. MS...Coastal Flood Advisory until 6 AM CST Friday for MSZ086-087.

GM...None.