In the afternoon hours on July 16th, isolated thunderstorms developed due to very moisture rich Gulf air in place combined with ample afternoon destabilization. Weak wind flow aloft allowed for slow movement with these storms leading to isolated areas of flash flooding to develop.
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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.
In the afternoon hours on July 16th, isolated thunderstorms developed due to very moisture rich Gulf air in place combined with ample afternoon destabilization. Weak wind flow aloft allowed for slow movement with these storms leading to isolated areas of flash flooding to develop.
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 Jul 16, 2:38 AM CST, 10 hours earlier.
Area Forecast Discussion National Weather Service New Orleans LA 338 AM CDT Fri Jul 16 2021 .SYNOPSIS... Bermuda high continues to ridge southwestward across the northern Gulf Coast into Texas. Aloft, troughing extends southward across much of the Mississippi River Valley, with a bit of a weakness along the central Gulf Coast. A few showers noted on radar at 3 AM CDT, mainly over marine areas, and less areal coverage than what we saw at this time yesterday morning. Temperatures mid 70s to around 80 at 3 AM, not really unusual for mid July. && .SHORT TERM (through Sunday night)... As has been the case, seemingly endlessly this summer, the main threat in the forecast will be the daily convective potential. With weak upper troughing in place, there's really nothing to suppress the daily convective threat. Precipitable water values during the afternoons will generally be in the 2.1 to 2.3 inch range over a good portion of the area each afternoon. Convection allowing models indicate that areal coverage will be rather limited over land for most of the morning until the atmosphere reaches the convective temperature, which is forecast to be in the upper 80s each day. Most likely points for development will be along land/seabreeze boundaries, then spreading northwestward in the weak low level flow. Wind fields are expected to remain rather light, so storm motion will be rather slow, 5 mph or less. Efficient rain processes will mean there is at least the prospect of localized street flooding with the most persistent storms each day. As we lose surface heating late afternoon/early evening each day, most, if not all, convection should dissipate. Most areas should see high temperatures in the upper 80s to around 90, and guidance has this well in hand. Little change made to blended numbers, perhaps bumping up a degree or so in some locations to fit most recent trends. 35 && .LONG TERM (Monday and beyond)... This portion of the forecast is virtually no change from what we've been seeing locally for the last few months, and especially over the last couple weeks. The trough that enters the Mississippi Valley Friday will finally slide southeast and dig across the Appalachian Mountains and southwestward. This will send a slow moving frontal boundary towards the CWA. Model solutions indicate that the boundary stalls along the I-20 corridor, as opposed to solutions 24 hours ago showing the front reaching I-12. Either way, it will provide at least some degree of enhancement for convective development. The closer it is to the CWA the greater the heavy rain threat will be. The reason is that a pool of very moist air will be draped across the Gulf Coast region. GFS PW forecast shows that those values will be in the 2.2" to 2.4" range. Thus, the potential exists for heavy rain across the CWA. On Tuesday, models indicate that the base of the trough will pinch off and drift westward into Texas. As it does so, a broad low will be trying to develop. This will only continue to enhance shower and thunderstorm development. As with Monday, a near 100% coverage will be probable as well as the chance for heavy rainfall. Expect convective initiation early in the morning, if not really already ongoing (in weaker fashion) during the overnight to morning timeframe. This wet pattern, maybe not to the same degree of intensity as the frontal boundary and broad low washes out, will continue Wednesday into Thursday. In fact, beyond 7 days looks pretty much like this. Expect to see daily storm coverage increasing steadily from 10am to 2pm with isolated storms producing locally heavy rainfall. On a day to day basis, most rainfall totals will be less than an inch. However, isolated areas may see upwards of a few inches. The good news is high rain chances means more cloud cover and temps at to below normal. Even have highs only in the mid 80s on some days late in the forecast period. MEFFER && .AVIATION... A mix of VFR to barely MVFR ceilings will be possible this morning. By 15z, scattered convection will return and VCTS wording will be in place to reflect this convective risk at all of the terminals through the afternoon and early evening hours. Once again, after convection dissipates, most of the overnight hours will see VFR conditions. && .MARINE... Outside of the typical risk of thunderstorms and waterspouts each day, very benign conditions are expected over the coastal waters through early next week. The thunderstorm and waterspout risk will be most pronounced in the morning hours with convective development easing by the afternoon as a seabreeze pattern takes hold each day. A broad ridge of high pressure will extend from the eastern Gulf across the coastal waters, and this will keep a prevailing onshore flow of around 10 knots in place through the period. Seas will generally remain at 3 feet or less. && .PRELIMINARY POINT TEMPS/POPS... MCB 89 72 90 73 / 70 20 80 20 BTR 90 74 90 74 / 70 30 90 10 ASD 90 75 90 75 / 70 20 80 20 MSY 90 78 91 78 / 80 20 80 20 GPT 89 76 89 75 / 60 30 70 30 PQL 89 75 90 75 / 60 30 70 30 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...None. GM...None. MS...None. GM...None. &&
Special Weather Statement
National Weather Service New Orleans LA
949 AM CDT Fri Jul 16 2021
MSZ081-161515-
Harrison-
949 AM CDT Fri Jul 16 2021
...A STRONG THUNDERSTORM WILL AFFECT CENTRAL HARRISON COUNTY...
At 948 AM CDT, a strong thunderstorm was located over Gulfport,
moving north at 10 mph.
Winds in excess of 30 mph are possible with this storm.
Locations impacted include...
Gulfport, Biloxi, Long Beach, Lyman and Gulfport Airport.
This includes Interstate 10 in Mississippi between mile markers 29
and 44.
Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
LAT...LON 3042 8894 3043 8899 3042 8901 3039 8895
3038 8907 3036 8909 3036 8911 3035 8914
3035 8919 3054 8918 3051 8891
TIME...MOT...LOC 1448Z 188DEG 8KT 3041 8908
MSWSpecial Weather Statement
National Weather Service New Orleans LA
1104 AM CDT Fri Jul 16 2021
MSZ081-082-161630-
Jackson-Harrison-
1104 AM CDT Fri Jul 16 2021
...A STRONG THUNDERSTORM WILL AFFECT NORTHEASTERN HARRISON AND
WESTERN JACKSON COUNTIES...
At 1104 AM CDT, a strong thunderstorm was located 7 miles north of
Latimer, or 11 miles north of St. Martin, moving northeast at 20 mph.
Winds in excess of 30 mph are possible with this storm.
Locations impacted include...
Ocean Springs, Latimer, Vancleave, Gulf Hills, Gulf Park Estates,
Hickory Hills and Wade.
This includes Interstate 10 in Mississippi between mile markers 51
and 60.
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
LAT...LON 3037 8873 3062 8904 3068 8894 3067 8889
3071 8889 3074 8885 3074 8863 3059 8854
TIME...MOT...LOC 1604Z 241DEG 16KT 3060 8885
MSWSpecial Weather Statement
National Weather Service New Orleans LA
1201 PM CDT Fri Jul 16 2021
MSZ081-082-161730-
Jackson-Harrison-
1201 PM CDT Fri Jul 16 2021
...A STRONG THUNDERSTORM WILL AFFECT EAST CENTRAL HARRISON AND
SOUTHWESTERN JACKSON COUNTIES...
At 1200 PM CDT, a strong thunderstorm was located over St. Martin,
moving north at 5 mph.
Winds in excess of 30 mph are possible with this storm.
Locations impacted include...
Biloxi, Ocean Springs, St. Martin, D'iberville, Latimer, Gulf Hills
and Gulf Park Estates.
This includes the following Interstates...
Interstate 10 in Mississippi between mile markers 40 and 57.
Interstate 110 in Mississippi near mile marker 1, and between mile
markers 3 and 4.
Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
LAT...LON 3036 8877 3037 8885 3038 8885 3038 8878
3043 8885 3042 8894 3040 8886 3039 8886
3039 8900 3041 8900 3042 8897 3043 8900
3054 8900 3050 8868
TIME...MOT...LOC 1700Z 194DEG 6KT 3041 8889
MSWSpecial Weather Statement
National Weather Service New Orleans LA
113 PM CDT Fri Jul 16 2021
LAZ061-063-064-077-161845-
Western Orleans-Upper St. Bernard-Upper Plaquemines-Upper Jefferson-
113 PM CDT Fri Jul 16 2021
...A STRONG THUNDERSTORM WILL AFFECT NORTHWESTERN ST. BERNARD...
SOUTHWESTERN ORLEANS AND NORTH CENTRAL JEFFERSON PARISHES...
At 113 PM CDT, a strong thunderstorm was located near Gretna, or near
Marrero, moving north at 10 mph.
Winds in excess of 30 mph are possible with this storm.
Locations impacted include...
New Orleans, Metairie, Marrero, Harvey, Avondale, Timberlane, Belle
Chasse, Chalmette, Jefferson, Gretna, Harahan, Westwego, Elmwood,
Terrytown, Bridge City, Arabi and Woodmere.
This includes the following Interstates...
Interstate 10 in Louisiana between mile markers 227 and 243.
Interstate 610 between mile markers 1 and 4.
Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
LAT...LON 2989 9021 3002 9019 3002 9011 3003 9009
3004 9005 3002 8995 2985 9001
TIME...MOT...LOC 1813Z 195DEG 10KT 2995 9009
MSWThe national radar mosaic for the moment the first event began.
1 flash flood. Local standard time, as filed.
Report of high water on the Paris Avenue underpass near Gentilly Boulevard. High water reported across roads in the area.
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, July 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: 974447.