textproduct: New Orleans/Baton Rouge

KEY MESSAGES

Updated at 1139 AM CST Thu Dec 11 2025 - Little or no rain expected through Saturday. Higher rain chances Saturday night into Sunday morning with a cold front.

- The coldest air of the year will bring dangerous wind chills and a widespread freeze to the area Sunday night into Monday morning.

- Strong winds approaching gale force and dangerous seas are expected Sunday into Monday after a strong cold front moves through.

SHORT TERM

(This afternoon through Saturday Night) Issued at 1139 AM CST Thu Dec 11 2025

A more zonal and southern stream focused mid to upper level flow pattern will develop tonight into tomorrow over the area and remain in place through Saturday. Embedded within this zonal flow regime, a weak southern stream vorticity max will slide through the northern Gulf Friday night into Saturday. In the low levels, a broad surface high extending from Florida westward across the eastern Gulf will keep a persistent southerly flow in place starting tonight and lasting through Saturday. Low level warm air and moisture advection from the Gulf will take place over the period, and this will allow PWAT values to rise to between the 50th and 75th percentile for this time of year, or around 1 to 1.1 inches. This increased moisture will combine with the weak forcing from the passing vort max Friday night into Saturday to form scattered offshore showers. Over land, a few low topped showers will form over this period, but the bigger threat is the increased potential for fog development late Friday night into Saturday morning. Fog probabilities are highest for areas to the north and west of Lake Pontchartrain including the Northshore, metro Baton Rouge, southwest Mississippi, and the River Parishes, and fog is included in the forecast for these areas. Temperatures will remain cool tonight with the coldest readings in the upper 30s in the Pearl and Pascagoula River basins and the rest of the region falling into the 40s. However, the southerly flow will help push readings above average starting tomorrow and lasting through Saturday with highs upper 60s and lower 70s and lows in the 50s.

Saturday night is another pattern shift as a very strong northern stream trough digs into the eastern half of the CONUS. This will drive a strong arctic cold front southward and into the area by the late overnight hours. All of the model guidance is in remarkably good agreement on the timing of this system, so confidence is high that the system will move through in the late Saturday night time period. As the shallow cold pool moves into the area and lifts the warmer and more unstable airmass in place, a broad area of post-frontal light stratiform rain will develop across the area late Saturday night. Some moisture pooling ahead of the front will also push PWATS up to the 75th percentile or around 1.2 inches briefly late Saturday night, but the moisture depth will be limited to 700mb and lower. Given this, deeper convection appears to be unlikely even with more favorable lapse rates in the 700mb to 500mb level. The light stratiform rainfall should come to end by mid-morning on Sunday as the front races offshore and much drier and colder airmass begins to move into the region.

LONG TERM

(Sunday through Wednesday) Issued at 1139 AM CST Thu Dec 11 2025

This much drier and colder airmass mentioned in the short term section will be the main weather concern in the long term period. Probabilities of temperatures below 32 degrees have increased across the entire area for Sunday night into Monday morning due to the orientation of the northern stream trough shifting further west and digging deeper into the region. The model trends have captured this with the guidance is surprisingly decent agreement that a widespread freeze with dangerous overnight wind chills will take place Sunday night into Monday morning. The NBM has high probabilities of over 80 percent that a hard freeze will also impact areas north and west of Lake Pontchartrain including all of southern and coastal Mississippi. For metro New Orleans and coastal Louisiana, the probabilities of a hard freeze range between 20 and 30 percent, but the probabilities of a light freeze are much higher at 70 to 80 percent. Given this, there is higher than average confidence that a significant widespread freeze event will occur Sunday night. Winds will also be breezy, so wind chills will fall into the teens along and north of the I-10/12 corridor and the low to mid 20s south of this corridor. Cold weather products have a high chance of being issued over the weekend for this event.

Fortunately, the cold snap will be short-lived as the trough quickly pulls to the east and a broad upper level ridge axis starts to build in from the west on Tuesday and Wednesday. As the heart of the 925mb thermal trough axis pulls east, high temperatures will warm from the mid to upper 40s on Monday to the upper 60s and lower 70s by Wednesday. Lows will also warm from the 20s and 30s Monday night into the upper 30s and 40s by Tuesday night. These warmer temperatures will be in response to a southerly flow redeveloping and spreading increasing low level moisture and warm air advection from the central Gulf waters into the area.

The upper level ridge will quickly push east on Wednesday as a fast moving southern stream shortwave trough axis approaches from the west. Strong moisture advection on Wednesday will help to push PWATS above average. Isolated to widely scattered shower activity could form as a broad area of upper level forcing associated with a region of positive vorticity advection ahead of the trough moves over the area taps into the available moisture and weak instability.

AVIATION

(18Z TAFS) Issued at 1139 AM CST Thu Dec 11 2025

VFR conditions will be the rule at nearly all of the terminals through the period. However, conditions look marginally favorable for some light fog to form at BTR, and the forecast has MVFR visibility restrictions due to fog in the forecast between 13z and 15z tomorrow morning. Otherwise, there are no concerns to aviators through the entire forecast period.

MARINE

Issued at 1139 AM CST Thu Dec 11 2025

Light onshore winds of 10 knots or less and calm seas of 2 feet or less will persist over the waters through Saturday as a broad area of high pressure remains centered over the region. A rapid change in conditions will then take place Saturday night and Sunday morning as a very strong cold front moves through. Winds will turn northerly and increase in speed to between 25 and 35 knots with higher gusts from Sunday afternoon through Monday morning. There is a decent probability that a gale warning will be issued for the waters over this time period due to high winds and rough seas anticipated. 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.

PRELIMINARY POINT TEMPS/POPS

MCB 40 69 52 70 / 0 10 20 20 BTR 43 70 55 73 / 0 20 10 20 ASD 40 70 52 72 / 0 10 10 20 MSY 48 71 58 72 / 0 10 10 10 GPT 44 68 55 69 / 0 10 10 20 PQL 40 69 52 70 / 0 10 10 20

LIX WATCHES/WARNINGS/ADVISORIES

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