Gulf moisture surging into the local area pushed precipitable water values to above the 90th percentile for this time of year. At the same time, an upper level trough was digging into Texas.
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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.
Gulf moisture surging into the local area pushed precipitable water values to above the 90th percentile for this time of year. At the same time, an upper level trough was digging into Texas. Showers and thunderstorms began developing ahead of this feature. A weak wind field in place was a prime environment for a slow moving storm to produce 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 Sep 28, 2:40 PM CST, 2 hours 20 minutes earlier.
Area Forecast Discussion National Weather Service New Orleans LA 340 PM CDT Tue Sep 28 2021 .SHORT TERM (Tonight through Thursday Night)...A broad upper level trough over the Rockies will continue to push a series of weak upper level vorticity maxima into the Lower Mississippi Valley through Thursday night. At the same time, favorable jet dynamics will support additional forcing aloft as the region resides within the right entrance region of the sub-tropical jet. In the low to mid-levels a ridge axis will remain centered over the eastern Gulf and Florida, and this will allow for continued deep layer moisture advection into the region through the period. This moisture is reflected well by expected precipitable water values of 2 to 2.1 inches. These values are well above the climatological averages for late September. This combination of increased upper level omega and moisture will support the continued development of convective activity both Wednesday and Thursday. The convection will tend to be diurnally driven with activity peaking in the late morning and afternoon hours. The other concern will be the potential for another low level inversion to form late tonight into early tomorrow morning. Boundary layer decoupling looks likely tonight given the weak boundary layer flow in place, and the high relative humidity in place will support the formation of low stratus and fog around sunrise tomorrow. Similar conditions look to be in place for another round of low stratus and fog development on Thursday morning. .LONG TERM (Friday through Monday Night)...The models and ensembles are in fairly good agreement on the overall pattern evolution over the weekend and into early next week. Friday should see a mid to upper level ridge centered over the eastern Gulf expand westward across the forecast area. The broad upper level trough will also continue to reside over the Rockies, but should retrograde and weaken slightly. As a result, a lower chance of convective activity is expected as temperatures warm slightly aloft and lapse rates weaken. There will be a fairly sharp POP gradient with higher POP in the chance to likely range of 40 to 60 percent over the far western zones and POP of 20 percent or less over the far eastern zones where the influence of the ridge is expected to be strongest. Similar conditions are expected on Saturday as the ridge remains firmly entrenched over the central and eastern Gulf. Conditions will turn more unsettled as the low parked over the Four Corners quickly lifts to the northeast across the Plains and into the Midwest Saturday night into Sunday. As the low pulls to the northeast it will begin to shear out and convert over to a more open shortwave trough axis. There is some disagreement on the strength of this trough between the various models, but there is stronger agreement on the timing. Fully expect to see a round of showers and thunderstorms accompany the passing trough axis, and POP should be higher than seen on Friday and Saturday across the forecast area. By early next week, another pattern shift is expected to take hold as a closed low forms over the Midwestern states. This will keep the forecast area in a deep layer westerly flow pattern for Monday and Monday night. Jet dynamics looks favorable for additional convective development by Monday afternoon across the forecast area, and have chance POP of around 40 percent in place to reflect this risk. && .AVIATION...Another round of low stratus and fog will be the primary concern at KBTR, KHDC, KMCB, and KASD around daybreak tomorrow. IFR or lower conditions will be possible. Another round of showers and thunderstorms should then begin to develop after 15z, and this could result in brief periods of gusty winds and IFR visibilities. && .MARINE...A persistent southeast flow of 10 to 15 knots is expected to continue through the weekend and into early next week as a broad ridge of high pressure dominates the Southeastern states. Winds may briefly approach exercise caution criteria of 15 to 20 knots over the outer waters at times this weekend, but the duration is not expected to be long enough to produce any significant impacts to maritime operations. Scattered thunderstorm activity will also be persistent through Thursday, and some of these storms could produce waterspouts and gusty winds. && .PRELIMINARY POINT TEMPS/POPS... MCB 69 82 67 83 / 30 70 50 70 BTR 71 84 69 85 / 30 80 50 70 ASD 71 84 69 84 / 40 70 40 60 MSY 74 83 72 84 / 50 80 40 60 GPT 72 82 70 82 / 40 50 30 50 PQL 71 84 68 85 / 30 50 30 40 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...None. GM...None. MS...None. GM...None. && PG
Special Weather Statement
National Weather Service New Orleans LA
1238 PM CDT Tue Sep 28 2021
MSZ082-281845-
Jackson MS-
1238 PM CDT Tue Sep 28 2021
...A strong thunderstorm will impact portions of northern Jackson
County through 145 PM CDT...
At 1238 PM CDT, Doppler radar was tracking a strong thunderstorm 8
miles northwest of Wade, or 14 miles south of Lucedale, moving east
at 15 mph.
HAZARD...Winds in excess of 40 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
Locations impacted include...
Big Point, Hurley, Wade and Vancleave.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is also occurring with this storm and may lead to
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 3060 8881 3073 8882 3074 8841 3054 8840
TIME...MOT...LOC 1738Z 277DEG 13KT 3072 8865
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...40 MPH
TDBThe national radar mosaic for the moment the first event began.
1 flash flood. Local standard time, as filed.
Veronica Drive in Chalmette was 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, September 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: 986770.