textproduct: New Orleans/Baton Rouge

KEY MESSAGES

Updated at 546 PM CST Thu Dec 4 2025 1. An area of low pressure near the coast will bring widespread rain and embedded thunderstorms to the area today through Saturday morning. 3-day rainfall totals will generally be 1.5" to 3" along the I-10/12 corridor with locally higher amounts as high as 6" especially west of I-55.

2. There is a marginal threat of excessive rainfall with this system today where locally higher rain totals of 2" to 4" in a approximately 6 hour period could result in flash flooding of urban and poor drainage areas. Locally higher amounts upwards of 5" cannot be ruled out for the rest of the day.

3. The slow-moving frontal boundary associated with this low will clear land areas tonight. Drier air filtering in will lower rainfall rates and reduce the risk for excessive rainfall and flash flooding. Additional rainfall of up to 3" could occur mainly along and east of the I-55 corridor. However, most areas are likely (>50%) to see between 0.5" and 1.5" with scattered shower activity Friday through Saturday.

SHORT TERM

(This evening through Friday night) Issued at 1208 PM CST Thu Dec 4 2025

The entire area has at least seen some rainfall today as a surface low pressure makes its way along the northern Gulf coast. A 925mb frontogenetic band that set up across the Florida Parishes produced localized rainfall amounts of 5-6 inches this morning. Since then, that main banding has moved off to the east more progressively than this morning and has mostly pushed offshore of the MS Coast. Another 925mb frontogenetic band is seeming to set up across the Atchafalaya Basin this afternoon with lesser rain rates of 0-5-1 inch per hour. These rates are lower than what we saw this morning with the heavy rain across the Florida Parishes, but this one seems like it will affect more populated areas such as Baton Rouge and its surrounding areas. The rain rates as they stand now would not be much of an issue, but if that banding does intensify, then we could see a renewed flash flood threat, mainly for urban areas near and south of Baton Rouge. Rain totals with this new band will likely be in the 1-2 inch range. Drier mid- level air looks to approach the area from the northwest by 7pm, pushing the rain eastward with it. So, expect most of the rain to be out of the area by midnight tonight as that drier air moves in.

Drier air at 850mb looks like it will stick around from tonight and through Friday. This will bump down overall PW values from 1.7-1.8 inches today down to 1.3-1.4 inches (in between the 75th and 90th percentile for this time of year). This drier air will look to keep rain mostly scattered throughout the day tomorrow. Can't totally rule out a band or two across the area, but rain totals with those, if they form, would be up to an inch of rain. Also with the main low pulling away from the area, winds will continue to relax in response to this. So, instead of a cloudy and rainy day such as today, it'll mainly be a cloudy day tomorrow with scattered showers, not widespread.

LONG TERM

(Saturday through Wednesday night) Issued at 1208 PM CST Thu Dec 4 2025

Another impulse in the southwesterly mid-level flow looks to come from the Baja Peninsula and track across northern Mexico and into the northern Gulf Saturday evening and into Sunday. This impulse will spin up another low pressure in the Gulf by Saturday night. This will help to increase PW back to 1.8-2 inches along the SE LA coast. Yet another frontogenetic band looks to form with this low, but way farther south along the SE LA coast as well, so a narrow band of higher rainfall of 2-4 inches is expected late Saturday and into Sunday. thankfully, with this band expected to set up along the coast, there is very little flash flood threat due to those areas being mostly wetlands and marshes.

Drier upper-level air will filter into the area starting Sunday afternoon as an impulse pushes southward across the southern plains. This impulse also pushes a cold front coming through the area on Sunday afternoon, effectively sweeping any rain still left over from the repeated rounds of rain over the weekend. With the cold front, we will see our next shot of freezing temperatures Monday night and Tuesday morning. Since we have already had at least 2 freezes this season, there will not be freezing headlines, but we are expecting freezing temperatures across portions of the northern areas.

Timing, strength, and positioning of the next trough that will traverse the middle parts of the country mid-week differs a lot in the medium-range guidance. All of those things will have implications on if we see rain at all and how warm we get towards the end of the week. As models get into better alignment, the forecast will become more refined pointing one way or another.

AVIATION

(00Z TAFS) Issued at 546 PM CST Thu Dec 4 2025

Widespread SHRA continues to move from west to east across the area with most terminals seeing at least IFR CIGs and MVFR VIS conditions. SHRA is expected to taper off over the next 6 hours from west to east, but IFR CIGs will linger through the overnight hours. Winds will gradually shift from easterly to more northerly by sunrise at most terminals, some terminals along and north of I-10/12 already have seen this shift. Another round of -SHRA begins Friday afternoon and will spread from southwest to northeast across the area. Onset appears to be after 2100 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 1208 PM CST Thu Dec 4 2025

Winds have stayed elevated east of the Mississippi River as a developing surface low moves across the coastal waters. This will have multiple impacts with Small Craft Advisory conditions expected Thursday into Friday. 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. Winds will relax and return to offshore late Friday and then more variable on Saturday with the passage of another weak sfc low. A 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.

PRELIMINARY POINT TEMPS/POPS

MCB 42 50 44 56 / 70 60 60 60 BTR 44 52 46 59 / 70 60 70 60 ASD 44 56 44 59 / 80 40 70 80 MSY 51 57 51 61 / 70 40 70 80 GPT 48 57 47 59 / 80 40 80 80 PQL 45 58 44 59 / 80 40 70 90

LIX WATCHES/WARNINGS/ADVISORIES

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

GM...Small Craft Advisory until 6 AM CST Friday for GMZ530-532-534- 536-538-555-557-577.

MS...Coastal Flood Advisory until 6 AM CST Friday for MSZ086-087.

GM...Small Craft Advisory until 6 AM CST Friday for GMZ532-534-536- 538-555-557-577.