textproduct: New Orleans/Baton Rouge

KEY MESSAGES

Updated at 1225 PM CDT Thu Apr 30 2026

- Heavy rainfall and increased risk of flash flooding will impact much of the region Friday night. - The threat for thunderstorms, some possibly strong to severe will continue through Friday night.

- Cooler than normal high temperatures are expected Friday through Monday.

SHORT TERM

(Now through Saturday night) Issued at 1225 PM CDT Thu Apr 30 2026

An excellent setup for locally heavy rainfall to develop will remain in place through the entire short term period. A stalled frontal boundary will remain in place along the I-10 corridor PWATS will be near the daily maximum through tomorrow night. At the same time, favorable upper level jet dynamics will support continued deep layer forcing over the area. In the low to mid- levels a region of enhanced baroclinicity beneath the upper level jet couplet will allow a low pressure to form along the stalled front by tomorrow morning. This low will track to the east and help to increase both isentropic forcing behind the front and moisture convergence along the frontal boundary. Mean storm relative flow will be largely parallel the frontal boundary, so any storms that form will track along the boundary. This will allow for a greatly increased risk of training thunderstorms to form as early as late Friday afternoon, but more likely on Friday night when our flash flood threat peaks. Rainfall totals of 2 to 4 inches are generally expected over the next 2 days, but localized areas of 4 to 8 inches can be expected. Even with the latest high resolution modeling, the axis of heaviest rainfall will be highly dependent on exactly where the stationary boundary and greatest moisture convergence develops. The threat looks to be highest north of I-10 at this time, but if the boundary sinks further south than expected, that heavy rain axis could shift into metro New Orleans and the River Parishes. We will need to monitor the positioning of the front carefully as we move into tomorrow. We have also opted to hold off on issuing a flood watch due to the uncertainty in where the heaviest rainfall will occur.

Looking beyond the heavy rain concerns, ample instability and speed shear will also be in place to the south of the stalled frontal boundary through Friday night. 0-6km shear will remain on the order of 50 to 60 knots and areas south of the front will see MLCAPE values of 1000 to 1500 J/KG each afternoon. These values combined with the deep layer forcing over the region will support a risk of isolated severe thunderstorm development both this afternoon and again Friday afternoon for coastal Louisiana and the offshore waters. Although directional shear will be more limited at around 100 to 150 m2/s2 in the lowest 3km, some weak mesocyclonic development in the updraft will occur with any severe storms. Tornadoes are unlikely to occur, but these weakly rotating updrafts will support a larger hail formation as residence time increases in these longer lasting and deeper updraft cores. As the cores aloft finally exceed the buoyant forcing with the updraft, they will collapse and produce periods of severe hail and strong damaging winds in coastal Louisiana and offshore.

Temperatures will be much cooler than previous days due to the boundary being stalled over the area. Persistent cloud cover and periods of rain will combine with fairly strong cold air advection behind the front to keep temperatures in the 60s and lower 70s north of the front. South of the front, temperatures will remain warm with highs climbing into the upper 70s and lower 80s both today and tomorrow. A very small diurnal range is expected tonight and dewpoints remain very high with readings only cooling into the upper 50s and lower 60s north of the front and the upper 60s south of the front. By tomorrow night, temperatures and dewpoints will begin to drop quickly as the front pushes offshore late in the night. Lows should drop into the low to mid 50s by daybreak on Saturday.

A deep northern stream longwave trough axis will pass through the area on Saturday and this will help to fully drive all of the rain out of the area as a cold front sweeps out into the central Gulf. Breezy and significantly colder conditions will take hold by Saturday afternoon with northerly winds of 15 to 20 mph and temperatures in the upper 60s and lower 70s expected. The combination of clear skies and continued cold air advection into the area Saturday night will allow lows to cool into the upper 40s and lower 50s across most of the area. Only the immediate southshore of Lake Pontchartrain and the immediate coast of Louisiana will see lows in the mid 50s due to the warmer nearby waters modifying the temperatures slightly.

LONG TERM

(Sunday through Wednesday night) Issued at 1225 PM CDT Thu Apr 30 2026

A broad and deep low to mid-level high will remain in firm control of the forecast area on Sunday and Monday. Skies will remain largely clear and humidity will remain low as this high dominates the region. Temperatures will also run a bit below average with highs in the mid 70s Sunday afternoon and the upper 70s Monday afternoon. Lows will also remain cool Sunday night as clear skies, low dewpoints, and lighter winds allow temperatures to fall back into the upper 40s and lower 50s over inland areas. Coastal locations will once again fall into the mid 50s.

Tuesday and Wednesday will see the pattern shift once more. A zonal flow regime will develop in the upper levels while a persistent and deep layer onshore flow pattern will form on the western periphery of a departing high in the low to mid-levels. This onshore flow regime will allow for Gulf moisture and warmth to begin feeding back into the area. Tuesday will remain dry as the mid-levels remain dry and a capping inversion lingers, but as moisture deepens on Wednesday a passing southern stream vort max will allow for isolated to widely scattered convective activity to form Wednesday afternoon. This activity will be diurnally induced as temperatures warm into the mid to upper 80s and MLCAPE exceeds 1000 J/KG. Overall, a return to the warmer and more humid pattern seen recently is expected to return by the middle of next week.

AVIATION

(18Z TAFS) Issued at 1225 PM CDT Thu Apr 30 2026

IFR conditions will be the rule at all of the terminals throughout the entire forecast period as a stationary front lingers over the region. Periods of showers and thunderstorms will impact all of the terminals and this threat is reflected by TEMPO and PROB30 groups. As convection moves through, visibilities will fall to between 2 and 5 miles, resulting in periods of IFR and MVFR conditions. Ceilings will also vary between 500 and 2000 feet as the showers and storms move through.

MARINE

Issued at 1225 PM CDT Thu Apr 30 2026

Winds will be variable in direction this afternoon into tonight as a stationary front remains parked over the area. To the north of the front in the tidal lakes and sounds, northeast winds of 10 to 15 knots will persist into the overnight hours. South of the front, southeast winds of 5 to 10 knots will be the rule through tonight. Tomorrow, a developing low pressure system will move into the area along the front. Winds will increase in response to this low with northeast winds of 15 to 20 knots forming over the tidal lakes and sounds and southeast winds of 10 to 15 knots developing in the open Gulf waters. As the low tracks to the east, it will help drive the front offshore Friday night into Saturday. Strong northerly winds of 20 to 25 knots will develop Friday night and persist through Sunday morning over all of the waters, and a small craft advisory will be issued for these conditions by tomorrow. Winds and seas will quickly fall off to less than 10 knots and 3 feet Sunday night into Monday as a broad area of high pressure settles over the region. As the high shifts to the east on Tuesday, winds will turn southerly at around 10 knots.

LIX WATCHES/WARNINGS/ADVISORIES

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