A sea breeze boundary became the focus for afternoon thunderstorms. As storms began to develop, weak steering winds prevented them from moving very much.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS LIX wrote it up.
A sea breeze boundary became the focus for afternoon thunderstorms. As storms began to develop, weak steering winds prevented them from moving very much. This resulted in heavy rain over an extended period which led to flash flooding in the New Orleans area.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS New Orleans, LA wrote its last area forecast discussion before the first event at Jun 23, 2:28 AM CST, 9 hours 22 minutes earlier.
Area Forecast Discussion National Weather Service New Orleans LA 328 AM CDT Wed Jun 23 2021 .SYNOPSIS... Aloft, upper ridging over the Rockies, with a longwave trough over about the eastern third of the country. Water Vapor imagery indicates that drier air has pushed into the area from the north, although it wasn't really noticeable in surface observations. A subtle boundary was located somewhere around the Interstate 10 corridor, with main difference in airmasses being slightly cooler and drier on the north side of it. For the first time in quite a while, no precipitation noted on radar within our area of responsibility. Temperatures and dew points generally in the 70s across the area. && .SHORT TERM... No real indication of a shortwave moving into the area to trigger convection today, so it will be more meso to microscale factors, such as sea and lake breeze boundaries to produce thunderstorms. Areal coverage of thunderstorms should be a bit less than what we've seen the last couple of days, especially across the northern third of the area. While the LIX 00z sounding had precipitable water values in excess of 2 inches, the NAMBUFR sounding for McComb has values in the 1.5 to 1.7 range this afternoon. We may be a bit on the high side with PoPs for today, but our numbers are in agreement with neighboring offices. Would also note that while general QPF forecast doesn't carry any organized heavy rain, any heavy rain that occurs in the Interstate 10 corridor could produce problems as quite a few areas have seen close to a foot of rain in the last 5 days. Thursday and Friday are also likely to see somewhat limited amounts of convection, mainly along sea/lake breeze boundaries, as a small piece of the upper ridge to our west works its way into the area. This will mainly be during the diurnally favorable hours, afternoon on land and 2nd half of the night over coastal waters. Will trend high temperatures to the upper end of guidance, and occasionally above guidance. Most guidance has been consistently a few degrees on the cool side over the last week or so. Wouldn't be surprised to see some areas in the lower 90s, especially tomorrow. Overnight lows probably remaining in the lower/mid 70s for most of the area. 35 && .LONG TERM (Saturday and beyond)... Only minor tweaks made to the extended as previous forecast remains in line with latest thinking and guidance. Amplified upper trough remains entrenched in the middle of the country, leading to continued favorable pattern for daily showers and thunderstorms as local area position on the western periphery of the Bermuda high continues to bring in Gulf moisture. Expect to see a fairly typical diurnal fluctuation in rain chances. Most days should see scattered showers beginning near the coast during the morning hours and spreading inland throughout the day, with the greatest rain chances during the afternoon hours. Though rain chances will be high and moisture will be plentiful, the transient nature of the convection should keep rain totals in check most places. However, as is common this time of year, any given thunderstorm could drop a quick inch or two of rain. High rain chances and associated cloud cover should help keep afternoon highs from rising much above 90. Overnight lows should remain in the 70s. 95/DM && .AVIATION (12z TAF package)... Cigs will occasionally drop down to around FL010 feet as some lower clouds move over terminals through about 14z. Patchy FG at KMCB possible around sunrise. Conditions will be MVFR to VFR after 15Z today as TSRA gets fired up again, but areal coverage expected to be considerably less than what has been observed over the last few days. Conditions will improve after 00Z, with again a small potential for patchy FG at KMCB toward 12z Thursday. && .MARINE... Main marine concern over the next few days will continue to be the threat of thunderstorms. Prevailing winds will mostly top out in the 10 to 15 knots range through the weekend, so am not really anticipating any wind- related headlines over the coastal waters through the end of the week and weekend. && .PRELIMINARY POINT TEMPS/POPS... MCB 90 73 91 72 / 40 10 50 10 BTR 91 74 92 74 / 60 10 60 10 ASD 90 74 91 74 / 70 10 60 20 MSY 90 78 92 77 / 70 20 60 10 GPT 88 76 88 75 / 60 20 60 20 PQL 87 73 88 73 / 60 20 60 20 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...None. GM...None. MS...None. GM...None. &&
The national radar mosaic for the moment the first event began.
3 flash flood. Local standard time, as filed.
A member of the public reported numerous roads flooded near Elmwood.
Numerous roads in the Lower Garden District were flooded.
Multiple roads in Bridge City were impassible due to high water.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Louisiana in 2021Every state in 2021This day in weather historyWarnings in Louisiana, June 2021
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 968133, 968134, 968136.