An upper level trough brought a cold front to the region. Ahead of this cold front, moisture levels through the atmospheric column increased to above the 90th percentile for this time of year.
Every event with a place to put it. Tap one for its entry below.
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.
An upper level trough brought a cold front to the region. Ahead of this cold front, moisture levels through the atmospheric column increased to above the 90th percentile for this time of year. Ample instability in place combine with the abundant moisture and lift from the frontal boundary set the stage for numerous thunderstorms producing heavy rainfall and flash flooding.
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 21, 2:53 PM CST, 4 hours 37 minutes earlier.
Area Forecast Discussion National Weather Service New Orleans LA 353 PM CDT Mon Jun 21 2021 .SHORT TERM... Tonight through Thursday... Tonight into Tuesday morning, a frontal system is expected to move through our area, increasing rain chances. Southerly surface winds will help to enhance the lifting and moisture advection into the area. Upper level divergence will help to enhance buoyancy and help with efficiency. PW values will remain above the 75th percentile for the SPC sounding climatology for the next few days. These storms will have the potential for locally heavy rainfall overnight, especially in the vulnerable areas. Lightning will also be a concern overnight as well. Tuesday through Thursday, the frontal boundary will linger over the area. Wednesday and Thursday, the boundary refires convection, mainly during the afternoon hours. Southerly surface winds will help to enhance lifting and moisture advection over the area Tuesday through Thursday. PW values will remain over the 75th percentile for the next few days. Heavy rainfall inside of thunderstorm development will be a concern with this frontal system moving through, particularly Tuesday. Lightning will also be a concern as well. MSW .LONG TERM... Friday through Monday... Friday through Monday, more of a normal summertime pattern will begin to dominate the area. Rain chances will be enhanced, mainly during the afternoon hours. Southerly surface winds will help to enhance moisture advection in the atmosphere. PW values will remain high through this time period. Scattered thunderstorms and showers will be possible daily during the peak daytime heating hours. Lightning will be a concern inside thunderstorm development as well. MSW && .AVIATION... VFR conditions prevail at all area airports. Some vicinity showers will be possible through the afternoon hours. Temporary periods of showers and storms will be possible at all area airports which will cause lower visibilities and ceilings, and TEMPO groups are in place during the best timing for these showers and storms. Overnight tonight through the end of the forecast period, MVFR conditions will be possible due to low ceilings and vicinity showers. MCB may get to IFR conditions around daybreak tomorrow briefing due to fog and vicinity showers before returning to MVFR conditions for the end of the forecast period. MSW && .MARINE... Tonight through Friday, winds will be southerly and moderate (<15 knots). Friday afternoon through Monday, winds will be easterly to southeasterly and moderate (<15 knots). Wave heights will correspond to the wind speeds. MSW && .PRELIMINARY POINT TEMPS/POPS... MCB 71 83 70 89 / 80 80 20 50 BTR 73 86 73 90 / 80 90 30 60 ASD 73 86 72 89 / 80 80 40 70 MSY 76 87 76 89 / 80 80 40 70 GPT 74 85 74 87 / 90 80 40 70 PQL 72 84 72 87 / 90 90 50 70 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...None. GM...None. MS...None. GM...None. &&
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
638 PM CDT MON JUN 21 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0637 PM FLASH FLOOD 1 WNW SLIDELL 30.29N 89.80W
06/21/2021 ST. TAMMANY LA PUBLIC
4-6 IN OF STANDING WATER ON THE BACK PATIO.
&&
KOPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
642 PM CDT MON JUN 21 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0641 PM FLASH FLOOD SLIDELL 30.28N 89.78W
06/21/2021 ST. TAMMANY LA PUBLIC
SCATTERED REPORTS OF STREETS FLOODING.
&&
KOPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
707 PM CDT MON JUN 21 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0415 PM FLASH FLOOD 2 NE HARAHAN 29.96N 90.18W
06/21/2021 JEFFERSON LA PUBLIC
ROADS FLOODED.
&&
KOPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
712 PM CDT MON JUN 21 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0430 PM FLASH FLOOD 2 NW NEW ORLEANS 29.99N 90.11W
06/21/2021 ORLEANS LA PUBLIC
CANAL BLVD. UNDERPASS FLOODED.
&&
KOPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
749 PM CDT MON JUN 21 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0430 PM FLASH FLOOD 2 ESE METAIRIE 29.99N 90.14W
06/21/2021 JEFFERSON LA PUBLIC
ESTIMATED 6-8 IN OF WATER OVER THE ROAD
WAYS.
&&
KOSpecial Weather Statement
National Weather Service New Orleans LA
818 PM CDT Mon Jun 21 2021
LAZ061-064-070-075>078-MSZ080-220145-
Southeast St. Tammany-Western Orleans-Upper St. Bernard-Eastern
Orleans-Northwest St. Tammany-Lower St. Bernard-Upper
Jefferson-Hancock-
818 PM CDT Mon Jun 21 2021
...A LINE OF STRONG THUNDERSTORMS WILL AFFECT CENTRAL ST. BERNARD...
ORLEANS...SOUTHEASTERN ST. TAMMANY...NORTHERN JEFFERSON PARISHES IN
SOUTHEASTERN LOUISIANA AND SOUTHWESTERN HANCOCK COUNTIES...
At 818 PM CDT, radar indicated strong thunderstorms were located
along a line extending from near Metairie to near Meraux to near
Shell Beach. Movement was northeast at 35 mph.
Winds in excess of 40 mph are possible with these storms.
Locations impacted include...
New Orleans, Slidell, Metairie, East New Orleans, Chalmette, Lake
Catherine, Pearlington, Lacombe, Shell Beach, Arabi, Meraux, Violet,
Slidell Airport and Lakefront Airport.
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is also occurring with these storms, and may
cause localized flooding. Do not drive your vehicle through flooded
roadways.
LAT...LON 2977 8972 2994 8993 3000 9021 3018 8968
3026 8998 3039 8995 3031 8959 3019 8944
3016 8966 3015 8963 3002 8972 3002 8984
2994 8984 2996 8973 2987 8968 2987 8961
3008 8949 3005 8938
TIME...MOT...LOC 0118Z 218DEG 32KT 3003 9009 2999 8990 2987 8974
PGThe Mobile radar (KMOB), 71 km away, was scanning. The volume nearest the first event began at 01:27 UTC.
3 flash flood. Local standard time, as filed.
Broadcast media reported Rocky Mountain Drive, Olympia Way and Sierra Cove closed due to flooding.
Broadcast media reported via social media Wilkes Avenue closed due to high water.
Broadcast media shared a video of a car stalling in flood water on MS Highway 90 near Courthouse Road.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Mississippi in 2021Every state in 2021This day in weather historyWarnings in Mississippi, 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: 968107, 968108, 968109.