textproduct: New Orleans/Baton Rouge

KEY MESSAGES

Updated at 536 AM CDT Wed Jun 17 2026

- Potential for Life Threatening Flash Flooding

- A Flood Watch is in effect through Friday morning for most of southeast Louisiana as well as all of southwest and coastal Mississippi.

- Continuing to monitor Potential Tropical Cyclone One just off the south Texas coast as it moves northeast toward the northwest Gulf Coast on Wednesday. There is a high chance (70%) of development. Marine and heavy rain will be the primary impacts.

- River flooding potential exists as well with forecast areal rainfall amounts of 5 to 10 inches with isolated amounts much higher.

SHORT TERM

(Now through Saturday) Issued at 1240 AM CDT Wed Jun 17 2026

Shortwave troughs over Michigan and Montana, with ridging along the Pacific Coast. A tropical disturbance (Potential Tropical Cyclone One) was just off the lower Texas coast at late evening. A weak frontal boundary was over north Mississippi.

Most convection has shifted offshore in the last several hours, but there is still some light rain to the south of Interstate 10. Precipitable water values on the evening soundings around the region ranged from 2 to 2.2 inches. Those values are likely to increase slightly over the next 24 hours to 2.2 to 2.4 inches. Definitely have a deep warm cloud layer in place (500 mb temps -4 to -6C), so convection will likely have very efficient rainfall production.

Multiple locations across the CWA have already seen upwards of 5-8" rain, resulting in flash flooding. So while storms may move individually over the next 48 hours, repeated development along the same corridor could lead to quick rainfall totals of 2 to 4 inches, with isolated quite a bit higher where training occurs. Urban and poor drainage areas will be most vulnerable.

A secondary concern will be a low-end tornado threat. Low cloud bases, sufficient low-level shear (30kts), SRH 200-300 SRH, and boundary interactions could support a brief tornado or two, especially with any stronger surface-based storm that can interact with the stalled front or outflow boundaries. A few circulations occurred yesterday morning, and not much will have changed this morning. This threat should remain localized and conditional, but bears watching given the observed low-level shear and boundary- rich environment.

Today remains interesting. The low that prompted Tropical Storm Watches and Warnings for areas west of the CWA is forecast to track northeast along the Texas coast. CAMs are currently showing quite a bit less convection locally as that system approaches the northern Gulf Coast. That's likely as a result of subsidence on the periphery what NHC forecasts will be a tropical storm at some point later today. However, the atmosphere aloft will still be quite saturated. What you end up with is less convection, so more sunshine which allows for more warming and more instability. Weak low level wind field will be the biggest limit to TOR potential, but still think there's a low-end conditional threat, especially late this afternoon and tonight. Additionally, depending on how organized this system gets, there may be a need for a brief Wind Advisory at some point near the Atchafalaya River Basin.

Thursday carries a mix of threats similar to today, but in different ways. Remnant tropical low will be moving northeast of the area, but that will remain conducive for rain band training. This is something we've seen in the area time and time again. The result of this setup is widespread light/moderate rainfall totals with streaks of very high rainfall amounts. CAMs suggest a swath of 5 to 10 inch rain totals, but 10-20" isolated totals certainly within the range of possibilities. Like all events, if that's over Lake Pontchartrain or the Gulf, no one but the fish are impacted. If it's over land, many people get impacted. The other side of this setup potential is weak TORs embedded within any stronger rain bands, especially where differential heating enhances near- surface instability along boundary/outflow interactions within an already moist, low- LCL, and modestly sheared environment.

While the tropical system should exit the area on Thursday, the frontal boundary to the north isn't really going to help us dry out, as it will still be over northern Mississippi Saturday. Precipitable water values will still be around 1.8 inches, which is still above the 75th percentile, so there will still be enough moisture around to at least support scattered showers and storms Friday and Saturday. Not as much of a threat for heavy rainfall, but it still can't be ignored.

Temperatures likely won't get past the mid 80s today, but as the tropical system departs on Thursday, any glimpses of sunshine will probably allow temperatures to creep back closer to 90. On Friday and Saturday, a pretty good chance we get into the lower 90s. And with all the wet ground around, and dew points likely to be in the mid and upper 70s, it's probably going to be rather steamy any time the sun is out.

LONG TERM

(Saturday night through Tuesday) Issued at 1240 AM CDT Wed Jun 17 2026

Upper ridging is expected to be over the northeast and north central Gulf from Saturday night into Tuesday. Ridging further to the west is expected to build into Arizona early next week. A weakness between the ridges is expected to remain over Texas for the entire period. Any surface frontal boundaries are expected to remain north of our area through this period.

Precipitable water values will generally be in the 1.6 to 1.8 range for Sunday through Tuesday. This should keep the daily convective development in the isolated to scattered range Sunday, mainly north of Interstate 10, and generally dissipate after sunset. Monday and Tuesday should be mainly dry.

Highs likely to be in the lower and middle 90s. Lows in the mid and upper 70s.

AVIATION

(12Z TAFS) Issued at 536 AM CDT Wed Jun 17 2026

VIS and CIG reductions are again expected today with intermittent convection developing, especially later today and tonight. Could have isolated to scattered convection during the day today, so didn't change much from the prior package. Winds will be southerly and gradually increase through the day and overnight tonight, especially terminals west of I55. There is also a signal for LLWS for a few terminals later tonight. (Frye)

MARINE

Issued at 1240 AM CDT Wed Jun 17 2026

The tropical disturbance currently located just off the south Texas coast is forecast to track northeastward along the Texas coast before moving into western and central Louisiana tonight. The interaction between this feature and the strong high to the east will cause winds over local marine waters to increase via tightening pressure gradient. Forecast boundary layer winds well into the mid 20 knot range should be a good predictor for observed winds over the coastal waters. Thus, have issued a Small Craft Advisory for the next few days. Guidance suggests winds won't appreciably relax until at least Friday.

LIX WATCHES/WARNINGS/ADVISORIES

LA...Flood Watch through Friday morning for LAZ034>037-039-046>048- 056>058-064-071-076>087-089-090-092-094-096-098>100.

Coastal Flood Advisory until midnight CDT tonight for LAZ091-093- 095-097.

GM...Small Craft Advisory until 6 AM CDT Friday for GMZ529-531>536- 541-543-551-553-554-557-570-572-575-577.

MS...Flood Watch through Friday morning for MSZ068>071-077-083>088.

GM...Small Craft Advisory until 6 AM CDT Friday for GMZ531>536-541- 543-551-553-554-557-570-572-575-577.