A marginally severe environment resulted in generally disorganized scattered convection in the late afternoon. A weak convective line and separate cell produced severe wind gusts and isolated damage in portions of southeast and east central Missouri, respectively.
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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.
A marginally severe environment resulted in generally disorganized scattered convection in the late afternoon. A weak convective line and separate cell produced severe wind gusts and isolated damage in portions of southeast and east central Missouri, respectively.
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 Sep 4, 1:54 PM CST, 2 hours 51 minutes earlier.
Area Forecast Discussion National Weather Service Saint Louis MO 254 PM CDT Mon Sep 4 2023 .SHORT TERM... (Through Late Tuesday Afternoon) Issued at 253 PM CDT Mon Sep 4 2023 Key Messages: 1) Isolated-widely scattered convection will continue into the early evening before largely dissipating. While some storms may be strong, they are not expected to be severe. 2) Tuesday will be another hot and humid day with heat index readings between 95 and 100 degrees. Scattered thunderstorms will also be possible. 3) A cold front will move through the area on Wednesday with another chance for rain. The remainder of the week into the weekend will be cooler with near normal temperatures. Isolated to widely scattered showers and thunderstorms have developed this afternoon as an upper level low moves into southwest Missouri/northwest Arkansas. This convection will continue into the early evening as the low drifts northeast and opens up...finally becoming absorbed into the mean flow aloft tomorrow. The SPC mesoanalysis is showing around 2500 J/Kg MLCAPE this afternoon, but the deep layer shear is only 15-20kts. While some storms could briefly be strong, storms capable of producing 60 mph winds and 1 inch or larger hail seem unlikely at this time. The storms should weaken and largely dissipate by 02-03Z. Some weak, isolated convection may linger over southeast Missouri forced by mid-level vertical motion and upper level divergence out ahead of the low. Tuesday continues to look hot and humid, with well above normal temperatures and heat index readings between 95 and 100 degrees. It looks like scattered convection could redevelop in the morning due to weak to moderate low level moisture convergence, and continuing upward vertical motion as the base of the now open short wave swings through the Mid Mississippi Valley. ~2500 J/Kg MLCAPE provides potential for strong convection once again, but the weak shear will once again be the limiting factor for storms to reach severe strength. The shear does strengthen later in the afternoon, but by then most of the forcing looks like it will be east of the area. Carney .LONG TERM... (Tuesday Night through Next Monday) Issued at 253 PM CDT Mon Sep 4 2023 Guidance shows the short wave which is currently moving through Idaho/Montana moving into the Midwest on Wednesday morning. The surface reflection of the wave is forecast to be over Wisconsin at 12Z Wednesday with a trailing cold front dipping through the Mid Mississippi Valley into the southeast Plains. Models agree well on the position of the wave Wednesday morning, although there are differences on timing the FROPA through our area. Faster solutions have the front moving into eastern Illinois by 12-15Z, while slower models show the front lagging back into central Missouri at that time. This means the difference between a cooler and drier, or warmer and stormier forecast for Wednesday. The LREF favors the latter with the 1st and 3rd quartile CAPE hinting that the front will be extending from near Chicago south-southeast through central Illinois into the St. Louis Metro area and continuing southeast to near Springfield Missouri. This lends more confidence to the slower NAM and ECMWF solutions; and the current warmer forecast with 20-40 PoPs on Wednesday extending from southeast Missouri into southwest and south central Illinois still looks good. The pattern becomes more amplified toward the end of the week with a long wave trough over the eastern U.S. and a strong ridge over the west. The trough to our east locks relatively cool high pressure in across the Midwest and Great Lakes, and current indications are that this pattern won't break until sometime next week. There may be some lingering convection Thursday/Thursday night as the tail end of the front waves back to the north over parts of west/central Missouri. Otherwise, the high should keep us dry with near normal temperatures through the weekend. Carney && .AVIATION... (For the 18z TAFs through 18z Tuesday Afternoon) Issued at 1242 PM CDT Mon Sep 4 2023 Widely scattered showers and thunderstorms are possible this afternoon into early evening, primarily across southeast and east central Missouri into southwest and south central Illinois. Most of this convection should dissipate within an hour or two of sunset...though a few showers may linger or redevelop overnight. Otherwise, VFR flight conditions will prevail outside of thunderstorms. Gusty south-southwest flow will weaken and turn to the southeast overnight, and then restrengthen from the south Tuesday morning. Carney && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && WFO LSX
Hazardous Weather Outlook National Weather Service St Louis MO 255 PM CDT Mon Sep 4 2023 ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027- 034>036-041-042-047>052-059>065-072>075-084-085-099-052000- Greene IL-Macoupin IL-Montgomery IL-Bond IL-Fayette IL-Clinton IL- Marion IL-Washington IL-Randolph IL-Adams IL-Brown IL-Pike IL- Calhoun IL-Jersey IL-Madison IL-Saint Clair IL-Monroe IL-Knox MO- Lewis MO-Shelby MO-Marion MO-Monroe MO-Ralls MO-Pike MO-Boone MO- Audrain MO-Moniteau MO-Cole MO-Osage MO-Callaway MO-Montgomery MO- Lincoln MO-Gasconade MO-Warren MO-Saint Charles MO-Franklin MO- Saint Louis MO-Saint Louis City MO-Jefferson MO-Crawford MO- Washington MO-Saint Francois MO-Sainte Genevieve MO-Iron MO- Madison MO-Reynolds MO- 255 PM CDT Mon Sep 4 2023 This Hazardous Weather Outlook is for portions of eastern and central Missouri as well as west central and southwest Illinois. .DAY ONE...Tonight. Isolated to scattered thunderstorms are expected today over parts of the area into the early evening. A few storms may linger into the overnight hours. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. There is a chance of thunderstorms across portions of the area Tuesday through Thursday. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. Carney
The St Louis radar (KLSX), 104 km away, was scanning. The volume nearest the first event began at 22:44 UTC.
2 thunderstorm wind. Local standard time, as filed.
Multiple sources including the public and amateur radio operators reported estimated 60mph wind gusts in the Farmington area. Only minor tree damage was noted from the gusts.
One cell amidst a group of disorganized convection produced wind gusts strong enough to bring down multiple power poles along I-70 very near the Montgomery and Warren county line.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Missouri in 2023Every state in 2023This day in weather historyWarnings in Missouri, September 2023
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: 1148661, 1148663.