As an outflow boundary moved south across the forecast area, scattered showers and storms developed along it. Some of the storms produced heavy rain causing flash flooding.
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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 LSX wrote it up.
As an outflow boundary moved south across the forecast area, scattered showers and storms developed along it. Some of the storms produced heavy rain causing 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 St. Louis, MO wrote its last area forecast discussion before the first event at Aug 31, 11:05 PM CST, 2 hours 55 minutes earlier.
Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 1205 AM CDT Wed Sep 1 2021 .SHORT TERM... (Through Late Wednesday Night) Issued at 302 PM CDT Tue Aug 31 2021 Latest surface analysis indicated that a surface outflow boundary from thunderstorms earlier this morning was moving east across the CWA with a stationary front along the Missouri/Iowa border. There were showers and a few thunderstorms that developed earlier along this boundary, but they have since dissipated. Latest objective analysis continues to show a narrow window of 500-1000 MLCAPES ahead of this boundary with little CINH, so there remains some time the rest of the afternoon for scattered thunderstorms to develop. If they do develop, there remains the potential for a isolated strong wind gusts and heavy downpours. Also kept a slight chance of thunderstorms tonight as both the NAM/GFS are showing a weak shortwave dropping southeast across Missouri and Illinois this evening. Various CAMS are support at least isolated showers and thunderstorms tonight. By Wednesday, high pressure will build into the area bringing dry weather. Britt .LONG TERM... (Thursday through Next Tuesday) Issued at 302 PM CDT Tue Aug 31 2021 The majority of the ensemble members are showing that a upper ridge that will be over the area on Thursday will break down and that a upper trough will move from the northern Plains Great Lakes over the weekend. This will bring an attendant cold front that will move through the area on Saturday night. This will support a chance of showers and thunderstorms in the forecast Friday into Sunday as the front slowly moves through the area. The models are showing high pressure moving slowly into the area from the north early next week which will bring in drier air. Forecast plumes support highs in the low-mid 80s on Thursday and Friday that will slowly climb into the mid-upper 80s over the weekend into early next week. Britt && .AVIATION... (For the 06z TAFs through 06z Wednesday Night) Issued at 1153 PM CDT Tue Aug 31 2021 Showers and thunderstorms have moved southeast of the terminals. While a few isolated showers are possible overnight in/around the St. Louis metro terminals, probabilities appear too low to include anything in the TAFs. Therefore, the main concern will be stratus. Low-level flow out of the northeast suggests most of it overnight should be focused in central Missouri, with it exiting the KUIN vicinity imminently and the metro terminals likely being just far enough to the east. Tailored 6Z TAFs toward this scenario with a period of high IFR ceilings at KCOU and low MVFR conditions at KJEF. This stratus should gradually lift and then scatter out Wednesday morning. The remainder of the TAF period will be dry/VFR with light northeast surface winds. Gosselin && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && WFO LSX
Hazardous Weather Outlook National Weather Service Saint Louis MO 407 PM CDT Tue Aug 31 2021 ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027- 034>036-041-042-047>052-059>065-072>075-084-085-099-011200- Adams IL-Audrain MO-Bond IL-Boone MO-Brown IL-Calhoun IL-Callaway MO- Clinton IL-Cole MO-Crawford MO-Fayette IL-Franklin MO-Gasconade MO- Greene IL-Iron MO-Jefferson MO-Jersey IL-Knox MO-Lewis MO-Lincoln MO- Macoupin IL-Madison IL-Madison MO-Marion IL-Marion MO-Moniteau MO- Monroe IL-Monroe MO-Montgomery IL-Montgomery MO-Osage MO-Pike IL- Pike MO-Ralls MO-Randolph IL-Reynolds MO-Saint Charles MO- Saint Clair-Saint Francois MO-Saint Louis City MO-Saint Louis MO- Sainte Genevieve MO-Shelby MO-Warren MO-Washington IL-Washington MO- 407 PM CDT Tue Aug 31 2021 This Hazardous Weather Outlook is for portions of eastern and central Missouri as well as west central and southwest Illinois. .DAY ONE...Tonight. There is a chance of thunderstorms through tonight. A few of these storms may be strong to severe through early this evening. Damaging winds to 60 mph and brief heavy downpours are the main threats. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. There is a chance of thunderstorms Friday into Sunday across parts of the region. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed through early this evening. Byrd
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ST LOUIS MO
1012 PM CDT TUE AUG 31 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0923 PM TSTM WND DMG 2 WNW FRANKCLAY 37.87N 90.64W
08/31/2021 ST. FRANCOIS MO LAW ENFORCEMENT
TREE DOWN AT HIGHWAY 8 AND GERMANIA.
&&
KDPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ST LOUIS MO
1013 PM CDT TUE AUG 31 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0933 PM TSTM WND DMG 3 NNE BISMARCK 37.81N 90.60W
08/31/2021 ST. FRANCOIS MO LAW ENFORCEMENT
TREE DOWN OVER HIGHWAY 32 AND OLD IRONDALE
ROAD.
&&
KDPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ST LOUIS MO
1023 PM CDT TUE AUG 31 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0930 PM TSTM WND DMG 4 WNW BELLEVIEW 37.70N 90.82W
08/31/2021 IRON MO LAW ENFORCEMENT
TREE DOWN AT HIGHWAY 32 AND COUNTY ROAD 41.
&&
KDPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ST LOUIS MO
1028 PM CDT TUE AUG 31 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0905 PM TSTM WND DMG 1 ESE OLD MINES 38.01N 90.76W
08/31/2021 WASHINGTON MO LAW ENFORCEMENT
TREE DOWN AT HIGHWAY 21 AND HIGHWAY 47.
&&
KDPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ST LOUIS MO
1034 PM CDT TUE AUG 31 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0905 PM TSTM WND DMG 1 S OLD MINES 38.00N 90.77W
08/31/2021 WASHINGTON MO LAW ENFORCEMENT
POWER LINE KNOCKED OVER ALONG HIGHWAY 21.
&&
KDPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ST LOUIS MO
1036 PM CDT TUE AUG 31 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0928 PM TSTM WND DMG 1 ESE IRONDALE 37.83N 90.66W
08/31/2021 WASHINGTON MO LAW ENFORCEMENT
TREE DOWN ALONG NURSING HOME ROAD AND SCOUT
CAMP ROAD.
&&
KDThe Lincoln radar (KILX), 98 km away, was scanning. The volume nearest the first event began at 07:58 UTC.
1 flash flood. Local standard time, as filed.
Up to four inches of rain fell in a short amount of time causing flash flooding. Several roads were flooded in Irving and Witt. Also, Coffeen Road, and Filmore Trail were briefly flooded.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2021Every state in 2021This day in weather historyWarnings in Illinois, 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: 983515.