textproduct: New Orleans/Baton Rouge

KEY MESSAGES

Updated at 833 PM CST Sat Dec 13 2025 - The coldest air of the year will bring dangerous wind chills and a widespread freeze to the area Sunday night into Monday morning. A Cold Weather Advisory is in effect over this time period.

- Strong winds and dangerous seas are expected Sunday into Monday after a strong cold front moves through. Small Craft Advisories and Gale Warnings are now in effect for this time period.

UPDATE

Issued at 833 PM CST Sat Dec 13 2025

Dense fog advisory was issued earlier for coastal Mississippi and the accompanying waters. Advection/marine fog is impacting those locations right ahead of the approaching front and coastal MS saw conditions rapidly deteriorate. This will be a short window though as the fog should quickly improve once the cold front moves into that area during the early morning hours with fog transitioning into stratus. /CAB/

SHORT TERM

(This evening through Monday night) Issued at 1247 PM CST Sat Dec 13 2025

No significant changes in the overall forecast from before as the model guidance remains in very good agreement on the timing of a strong cold front that will pass through the region late tonight and tomorrow morning. A rapidly deepening northern stream trough will quickly descend into the eastern third of the CONUS tonight into tomorrow. As this trough deepens, the arctic airmass over the northern Plains will begin to sweep southward along the Mississippi Valley in the form of a fast moving frontal boundary.

Before the arctic airmass intrudes into the region, a very unseasonably moist and warm airmass will be over the area this evening into the late overnight hours with temperatures still sitting in the 50s and even lower 60s through late evening. Some moisture pooling will occur in advance of the front in the late evening and early overnight hours, and this will allow PWATS to climb to near the 90th percentile for this time of year. However, the moisture will be shallow, residing below 700mb. The shallow nature of the moisture and a lack of mid-level instability will keep any pre-frontal convective activity at bay. However, this warm and moist airmass will be easily lifted over the shallow cold pool to produce a period of post-frontal stratiform light to moderate rainfall late tonight into early Sunday morning. Rainfall totals should remain below a quarter of an inch. The rain will quickly come to an end by mid-morning tomorrow as the drier and colder arctic airmass moves in from the north. In fact, skies should be clear by the mid-afternoon hours based on the depth and strength of the arctic airmass moving in.

Although the main brunt of the colder air will remain well displaced to the north and east of the forecast area, we will still experience the coldest air we have seen this season with lows falling into the 20s and lower 30s Sunday night into Monday and highs only warming into the mid to upper 40s on Monday. For areas north of I-10/12, a hard freeze and a threat to pipes will exist tomorrow night as temperatures will remain below 25 degrees for several hours. In addition to the cold air temperatures, dangerous wind chills will take place tomorrow night across the region as gusty north winds of 10 to 20 mph persist through the night. Wind chill values will fall into the teens along and north of the I-10/12 corridor and the low to mid 20s further south. These wind chill values are low enough to prompt the issuance of a cold weather advisory for the entire area.

The thermal trough axis associated with the deep layer cold pool over the eastern third of the country will start to shift to the east Monday night, but that will not mean a return to milder conditions. After a chilly and sunny Monday with highs struggling to reach the mid to upper 40s per the latest 925mb temperature profiles, lows will easily fall back into the upper 20s and lower 30s for most of the region Monday night. Only the immediate coast of Louisiana and areas along the southshore of Lake Pontchartrain remaining in the mid to upper 30s.

LONG TERM

(Tuesday through Friday night) Issued at 1247 PM CST Sat Dec 13 2025

A return to a much warmer and more humid airmass will quickly happen as we move into Tuesday and Wednesday of next week. On Tuesday, the trough over the eastern CONUS will fully depart and a shortwave upper level ridge axis will slide in from the west. In the low to mid-levels, a broad high will also slide to the east. This will allow for a deep layer onshore flow pattern to develop, and PWATS will gradually climb back to more average levels for this time of year by Wednesday. A weak southern stream vort max will slip through on Wednesday night and Thursday, but limited mid and upper level moisture over the area will keep any shower activity isolated to widely scattered even as PWATS rise to over 1.2 inches. Once this system passes by, a zonal flow regime will develop over the area for Friday. A weak front will slightly cool temperatures, but only by a few degrees from the mid 70s on Thursday into the upper 60s on Friday. These temperatures are still well above average for mid-December.

AVIATION

(00Z TAFS) Issued at 833 PM CST Sat Dec 13 2025

Fog probabilities continue to remain high mainly for coastal MS and GPT. This is right ahead of the approaching cold front. As the cold front passes the fog will quickly improve but low clouds will still impact those terminals. Elsewhere low cigs will become an issue overnight but especially as the cold front moves across the region. MVFR to IFR cigs will impact all terminals likely bottoming out between 700-1300. CIGS should begin to improve from northwest to southeast around 14/15Z with all terminals back in VFR or very close to VFR around 18/19z. That said there will still be low clouds around they should just be above 3k ft by then. In addition scattered light rain will be accompany the front. /CAB/

MARINE

Issued at 1247 PM CST Sat Dec 13 2025

Light onshore flow and a warm and humid airmass moving across the cooler waters of the sounds and tidal lakes could support some fog development this evening into the early overnight hours. However, this fog will quickly clear later tonight as a front moves through all of the waters. A rapid change in conditions will take place tomorrow morning as a very strong cold front moves through. Winds will turn northerly and increase in speed to between 25 and 30 knots with higher gusts from mid to late morning tomorrow through Monday morning. Small Craft Advisories and Gale Warnings are in effect for the waters over this time period. Another high will then quickly settle over the area on Tuesday, and this will allow winds to turn more easterly and fall back to less than 10 knots. Seas will also begin to subside as the winds decrease Monday night into Tuesday. Wednesday and Thursday will see a slight increase in the onshore flow to 10 to 15 knots as the pressure gradient over the waters tightens in response to a passing shortwave feature, but no impacts to mariners are expected once we get past Sunday and Monday.

PRELIMINARY POINT TEMPS/POPS

MCB 41 47 21 48 / 70 10 0 0 BTR 46 52 24 49 / 60 20 0 0 ASD 47 57 22 49 / 40 30 0 0 MSY 52 59 32 47 / 30 30 0 0 GPT 48 57 26 49 / 40 30 0 0 PQL 47 57 22 49 / 40 30 0 0

LIX WATCHES/WARNINGS/ADVISORIES

LA...Cold Weather Advisory from 9 PM Sunday to 9 AM CST Monday for LAZ034>037-039-046>048-056>060-064>071-076>090.

GM...Small Craft Advisory from 6 AM Sunday to 9 AM CST Monday for GMZ530-532-534-536-538-550-552-555-557.

Dense Fog Advisory until 6 AM CST Sunday for GMZ532-534.

Gale Warning from 6 AM Sunday to 9 AM CST Monday for GMZ570-572- 575-577.

MS...Cold Weather Advisory from 9 PM Sunday to 9 AM CST Monday for MSZ068>071-077-083>088.

Dense Fog Advisory until 4 AM CST Sunday for MSZ083>088.

GM...Small Craft Advisory from 6 AM Sunday to 9 AM CST Monday for GMZ532-534-536-538-550-552-555-557.

Dense Fog Advisory until 6 AM CST Sunday for GMZ534.

Gale Warning from 6 AM Sunday to 9 AM CST Monday for GMZ572-575- 577.