textproduct: New Orleans/Baton Rouge

KEY MESSAGES

Updated at 613 AM CDT Thu Jun 18 2026

- Potential for Life Threatening Flash Flooding. A Particularly Dangerous and Life Threatening Flash Flood Situation exists with a High Risk of Flooding across portions of south Mississippi and southeast Louisiana, especially east of Interstate 55. Considerable Flash Flooding is likely and Catastrophic Flash Flooding is possible today.

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

- Tornado Watch 348 in effect until 6 AM CDT for most of the area.

- Dangerous conditions for mariners of small craft and minor coastal flooding on south facing shores west of the Mississippi River will persist through tonight as Post Tropical Cyclone Arthur moves into southwest Louisiana.

- Extreme heat is expected this weekend. Heat advisories will likely be issued for heat index values of around 110 degrees.

UPDATE

Issued at 354 AM CDT Thu Jun 18 2026

Updated Key Messages for WPC's High Risk of Excessive Rainfall today for portions of the area. Likely to have a fairly large stripe of 6 to 10 inch rainfall with isolated totals significantly higher from Houma and Thibodaux northeastward.

SHORT TERM

(Now through Sunday) Issued at 1220 AM CDT Thu Jun 18 2026

Post Tropical Cyclone Arthur has degenerated to a low pressure area along the Upper Texas Coast. The remnants will continue to track across western Louisiana overnight and will reach the Carolinas coastlines by Friday morning. We've already seen some rotation in radar data, and expect we'll have short-lived spinups overnight. Additionally, we remain highly concerned about extreme rainfall amounts overnight. We already had 2.3 inch precipitable water values at 00z, with guidance indicating that values near 2.6 inches are possible/likely overnight as a 35-40 knot low level jet plugs in. The 02Z HRRR, for instance, has a large area of rainfall totals in excess of 6 inches across the area by mid-afternoon Thursday with spot totals approaching or exceeding 10 inches. If these totals, or anything close are realized, we're probably looking at major flooding in those areas. No changes to Flood Watch anticipated. Could still be scattered precipitation into Thursday evening associated with this system before we start seeing some slight drying.

With precipitable water values remaining near 2 inches through Sunday, still plenty of moisture available for scattered convection, even without large scale forcing to aid in producing lift. The large scale heavy rainfall threat will diminish beyond Thursday evening, but localized heavy rain still possible. Could also see a few microbursts on Friday.

A second issue over the weekend will be heat stress. We'll likely see at least some sunshine at times Friday through the weekend that will allow temperatures to get into the lower, or possibly middle 90s in many areas. With dew points likely in the upper 70s to near 80, and lots of residual moisture on the ground, it's going to be steamy. Likely to have heat index values near our 108 degree criteria for Heat Advisories in many areas on Friday and possibly again on Sunday. This will be addressed once we get past the rainfall and tornado issues this morning. Overnight lows may have trouble getting below 80 degrees for several nights.

LONG TERM

(Sunday night through Wednesday) Issued at 1220 AM CDT Thu Jun 18 2026

Ridging sets up over the northern Gulf for the first half of next week. However, shortwaves will be tracking west to east just north of the local area. If we are going to have a day that is completely dry, it'll probably be Monday. Similar to the weekend, we'll have to monitor for potential Heat Advisories, especially Monday. For Tuesday and Wednesday, the question will be exactly when storms develop. If they develop early enough in the day, that would blunt the heat somewhat. For now, will stick with the NBM forecast temperatures with several days seeing highs in the lower and middle 90s.

AVIATION

(12Z TAFS) Issued at 613 AM CDT Thu Jun 18 2026

Large area of SHRA/TSRA moving across most terminals early this morning with IFR or lower conditions. Main exceptions are KHUM and KBTR, where convection has moved east for now. Eastern terminals could still see gusts to around 40 knots as convection moves through. The current area of convection should be east of all terminals by 18z, but with abundant moisture still in place, afternoon heating could redevelop TSRA. Expect any remaining precipitation to dissipate after sunset, but MVFR ceilings could redevelop before sunrise.

MARINE

Issued at 1220 AM CDT Thu Jun 18 2026

Strong southerly winds of 20 to 25 knots with gusts of 30 knots will remain in place over the coastal waters through tonight and into Thursday and seas of 6 to 9 feet can be expected in the open Gulf waters. Small craft advisories remain in effect due to these conditions. Moving into the weekend and early next week, a broad area of high pressure will build back over the eastern Gulf waters. Persistent onshore winds of 10 to 15 knots and seas of 2 to 4 feet can be expected from Friday through early next week.

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.

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.