A warm front across the region was the focus for thunderstorm development. There were numerous reports of large hail with the severe storms.
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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 warm front across the region was the focus for thunderstorm development. There were numerous reports of large hail with the severe storms.
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 May 13, 11:30 AM CST, 18 minutes earlier.
Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 1230 PM CDT Sat May 13 2023 .UPDATE... Issued at 1225 PM CDT Sat May 13 2023 Thunderstorms have begun forming along a convergent line nearing the Mississippi River just north of St Louis. Instability has maximized in our area today, with dewpoints in the low 70s and temperatures warming into the 80s, yielding surface based CAPE in excess of 3000. Wind shear is not overly strong, but sufficient for briefly organized storms. Low level easterly flow developing across Illinois will act to enhance the overall shear as storms move east. Development further south is expected as the storms encounter greater moisture and low level southeasterly inflow. Large hail has been the primary threat so far, but damaging winds are also becoming a possibility especially as storms form into a cluster and progress to the southeast through Illinois. Kimble && .SHORT TERM... (Through Sunday Night) Issued at 324 AM CDT Sat May 13 2023 (Today - Tonight) A warm front as of 0700 UTC was located near a KSTJ>>KSTL>>KMVN line this morning, growing more diffuse with southeastward extent. This boundary likely will serve as the focus for thunderstorm development this afternoon into the early evening as the warm front slowly moves poleward. Further southwest, generally weak convection in southeastern Kansas and northeastern Oklahoma (nearly in the same locations as 24 hours ago) is moving eastward. The storms are outflow dominant. Given this fact and a weakening low-level jet after sunrise, the expectation is for just some scattered showers and a few rumbles of thunder to reach parts of central and southeast Missouri this morning. By late morning, we likely will see a lull or complete dissipation in activity given the weakening low- level jet and associated moisture convergence. Around midday or shortly thereafter, additional storms should form near the warm front. There is some uncertainty on how widespread storms will be given that the front becomes more diffuse with east/southeast extent, and therefore, the convergence along it weakens. There should be enough instability (HREF probabilities for >2000 J/kg 40-50%) and adequate deep-layer shear (20-30 knots) for a few strong to severe thunderstorms. Convective mode is likely to be a combination of pulse storms and multicellular clusters, with a transient supercell or two possible in parts of northeast Missouri and west-central Illinois this afternoon where the deep-layer shear is strongest. Steep midlevel lapse rates and high amounts of CAPE within the hail-growth zone suggest hail is the main threat, though damaging winds are also possible along with a brief tornado potentially near the warm frontal boundary. A continued chance of showers and thunderstorms exists tonight, mainly in west central and south-central Illinois closer to the position of the warm front. Convective coverage is once again a question mark, as deterministic guidance suggests the best low- level moisture convergence to be well to our northeast overnight tonight in eastern Iowa and northern Illinois. In terms of severe chances, the expectation is for these storms to be sub-severe overnight due to lessening instability. (Sunday - Sunday Night) On Sunday, a midlevel shortwave trough is forecast to drop across the western Great Lakes and into the Ohio Valley. This feature is expected to help push the surface boundary southward as a cold front. This cold front is likely to serve as the focus for showers and thunderstorms through Sunday night. There remains some uncertainty on the exact timing of this front, but the most likely scenario is for thunderstorms to blossom in the afternoon hours along/behind the front and continue through the evening. The best coverage of storms will most likely be in parts of south central and southwest Illinois where surface convergence is expected to be strongest. A few of the storms on Sunday may be strong to severe, with large hail the primary threat given continued presence of steep midlevel lapse rates and tendency for storms to become more elevated with time on Sunday. Gosselin .LONG TERM... (Monday through Friday) Issued at 324 AM CDT Sat May 13 2023 (Monday - Wednesday Night) Behind Sunday's cold front, there is high confidence in a cooler and drier pattern for early/mid next week. While some shower activity may be possible with weak/subtle northwest flow shortwave troughs and associated secondary cold frontal passages, dry low-level air, nebulous/weak forcing for ascent, and instability remaining well south and west of the CWA all suggest most if not all of the area will stay dry. Temperatures on Monday will be the coolest of the period as 850-hPa temperatures drop back to near +10C and the anomalously strong surface high to our northwest has its most influence over the region. Highs in the low to mid 70s are forecast Monday afternoon, with a gradual warming trend through Wednesday. The coolest night of the period is expected to be Monday night into Tuesday morning, with a clear sky and light/variable winds in close proximity to the surface anticyclone. Forecast lows range from the low to mid 50s, but given dewpoints in the mid 40s, would not be surprised to see some 40s for lows in northeast Missouri and west- central Illinois. (Thursday - Friday) Ensemble guidance is in high agreement that mid/upper level northwest flow will continue to end the work week. Another shortwave trough is likely to transverse the Upper Midwest into the Great Lakes during the period, with a cold front moving across the Mississippi Valley. The specifics with these features is uncertain at this time, including but not limited to: the strength/timing of the midlevel shortwave trough and the timing of the cold front. This front should bring a chance of showers and thunderstorms. Ahead of the front, above normal temperatures are likely on Thursday, with cooler temperatures behind it on Friday. Ensemble guidance show that the air mass behind this front is likely to be cooler than the front moving through late Sunday. Anomalies of 850-hPa temperatures on both the GEFS/EPS are in the 4 to 6C range below normal for late May. Gosselin && .AVIATION... (For the 18z TAFs through 18z Sunday Afternoon) Issued at 1225 PM CDT Sat May 13 2023 Primary impact for TAFs is the timing of thunderstorms this afternoon. Storms have begun to form and so confidence has increased in the timing of storms moving through the metro in the next couple of hours. This looks like the primary threat window for today, with conditions improving after the storms move through. A cold front moves in from the north on Sunday and may bring some MVFR ceilings with it when it arrives at Quincy. It could also serve as a focus for more thunderstorm development on Sunday as it pushes southward. Kimble && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && WFO LSX
Hazardous Weather Outlook...CORRECTED National Weather Service St Louis MO 453 AM CDT Sat May 13 2023 ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027- 034>036-041-042-047>052-059>065-072>075-084-085-099-140845- 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- 453 AM CDT Sat May 13 2023 This Hazardous Weather Outlook is for portions of eastern and central Missouri as well as west central and southwest Illinois. .DAY ONE...Today and tonight. Scattered thunderstorms are forecast today. A few of these storms may be strong to severe between 1 and 7 PM with large hail the main threat. Damaging winds and a tornado are also possible. .DAYS TWO THROUGH SEVEN...Sunday through Friday. There is a chance for thunderstorms Sunday through Sunday night. A few of these storms may be strong to severe Sunday afternoon and evening with large hail the main threat once again. Another chance of thunderstorms exists across the area Thursday through Friday. .SPOTTER INFORMATION STATEMENT... Spotters are encouraged to report any hail or damaging winds to the National Weather Service in St. Louis. Gosselin
The St Louis radar (KLSX), 27 km away, was scanning. The volume nearest the first event began at 17:49 UTC.
6 hail. Local standard time, as filed.
A swath of large hail fell between Foristell and Wentzville/Flint Hill area. The largest hail stones reported were 1.5 inches in diameter.
A swath of very large hail fell in eastern St. Charles County. Areas that received large hail includes St. Peters, Harvester and St. Charles, mainly along and east of Jungermann Road. This includes the main street area of St. Charles.
A wide swath of large hail fell across northern portions of St. Louis County. Large hail was reported in Earth City, Maryland Heights, Bridgeton, St. Ann, Breckenridge Hills, Saint John, Overland and Woodson Terrace.
Another severe storm moved through the southern portions of St. Louis County. There were numerous reports of large hail. The hail was reported in Twin Oaks, Peerless Park, Valley Park, and Kirkwood.
Large hail was reported across the southern portions of the City of St. Louis.
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, May 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: 1105682, 1105684, 1105699, 1105703, 1105707, 1105710.